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diff --git a/34869-8.txt b/34869-8.txt new file mode 100644 index 0000000..24c17f1 --- /dev/null +++ b/34869-8.txt @@ -0,0 +1,3116 @@ +The Project Gutenberg EBook of The Essentials of Illustration, by +T. G. (Thomas George) Hill + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: The Essentials of Illustration + A Practical Guide to the Reproduction of Drawings & + Photographs for the Use of Scientists & Others + +Author: T. G. (Thomas George) Hill + +Release Date: January 7, 2011 [EBook #34869] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK THE ESSENTIALS OF ILLUSTRATION *** + + + + +Produced by Lesley Halamek, Chris Curnow and the Online +Distributed Proofreading Team at https://www.pgdp.net (This +file was produced from images generously made available +by The Internet Archive) + + + + + + + + + + THE ESSENTIALS OF ILLUSTRATION + + A PRACTICAL GUIDE TO THE REPRODUCTION + OF DRAWINGS & PHOTOGRAPHS + FOR THE USE OF SCIENTISTS & OTHERS + + By + T. G. HILL + + Reader in Vegetable Physiology in the University + of London, University College + + LONDON + WILLIAM WESLEY & SON + 28 Essex Street, Strand + 1915 + + +PRINTED BY THE WESTMINSTER PRESS, LONDON, W. + + + + +CONTENTS + + + PAGE + +INTAGLIO PRINTING 1 + + Intaglio plates 2 + + Line engraving 2 + + Etching 5 + + Soft-ground etching 6 + + Mezzotint 7 + + Photogravure 8 + +PLANE SURFACE PRINTING 15 + + Lithography 15 + + Chromolithography 20 + + Photolithographic processes 23 + + Collotype 23 + + The preparation of illustrated pages 26 + +RELIEF PRINTING 33 + + Woodcuts and engravings 33 + + The Half-tone process 37 + + The Half-tone three-colour process 46 + + Photomechanical line blocks 49 + + The drawing of microscopic details 67 + + The drawing of diagrams and apparatus 72 + + The drawing of maps 76 + + The drawing of graphs or curves 79 + + The swelled gelatine process 84 + +The Relative Cost of blocks and plates by + various processes 89 + +LITERATURE 95 + + + + +ILLUSTRATIONS + + +1. PLATES + +PLATE + + 1 An original lithograph by Mr. Harry Becker. + + 2 Chromolithograph. Messrs. Gerrards, Ltd. + + 3-5 Collotype. Messrs. André, Sleigh & Anglo, Ltd. + + 6 Half tone. Swan Electric Engraving Co., Ltd. + + 7 Half tone. \ + | + 8 Photogravure. | + | + 9 Collotype. | Messrs. André, Sleigh & + > Anglo, Ltd. + 10 Half tone. | + | + 11 Half tone. | + | + 12 Half tone three colour. / + + +2. TEXT FIGURES + + Tailpiece, p. 11. Electrotype from the original wood + engraving by Bewick. + + Tailpiece, p. 30. Line block. Messrs. Bourne & Co. + + Fig. 1. Wood engraving. + Messrs. Edmund Evans, Ltd. + + Fig. 2. Wood cut. Mr. G. N. Oliver. + + Figs. 3-6. Line blocks. + Messrs. André, Sleigh & Anglo, Ltd. + + Figs. 7 and 8. Line blocks, reproductions of a wood + engraving. Mr. C. Butterworth. + + Fig. 9. Line block. + + Figs. 10-13. Line blocks, reproductions of wood + engravings. + + Fig. 14. Line block. + + Fig. 15. Line block. + Messrs. André, Sleigh & Anglo, Ltd. + + Fig. 16. Line block. + Swan Electric Engraving Co., Ltd. + + Fig. 17. Line block. + Messrs. André, Sleigh & Anglo, Ltd. + + Figs. 18-20. Line blocks. + + Figs. 21-23. Line blocks. Messrs. Bourne & Co. + + Figs. 24 and 25. Line blocks. + + Fig. 26. Line block. Messrs. Bourne & Co. + + Fig. 27. Line block. + + Figs. 28 and 29. Line blocks. + Messrs. André, Sleigh & Anglo, Ltd. + + Fig. 30. Line block. Mr. C. Butterworth. + + Fig. 31. Line block. + Messrs. André, Sleigh & Anglo, Ltd. + + Fig. 32. Line block. Mr. C. Butterworth. + + Figs. 33 and 34. Line blocks. + + Figs. 35 and 36. Line blocks. + Messrs. André, Sleigh & Anglo, Ltd. + + Fig. 37. Line block. Messrs. Bourne & Co. + + Fig. 38. Lithograph reproduced by the Swelled + Gelatine Process. + Artists Illustrators, Ltd. + + Tailpiece, p. 86. Line block. + Messrs. André, Sleigh & Anglo, Ltd. + + + + +PREFACE + + +Modern scientific publications, although they may in some or even +many cases equal in their scientific quality the memoirs of earlier +workers, do not, on the average, reach a high standard as regards +illustration. For instance, in Great Britain botany is pre-eminent +in its morphological aspects; it should therefore follow that the +illustrations, which form so important a part of such papers, should +be beyond reproach. This is not always so, a fact which must be patent +to anyone with the slightest critical knowledge who looks through a +typical journal. This is a fact much to be regretted, since many of +the earlier scientists were accomplished draughtsmen and, indeed, +often artists; in this connection the Hookers and Professor Daniel +Oliver may be mentioned. The implication is not intended that there +are no good amateur draughtsmen nowadays; there are, and in some cases +possessed of great ability. The beautiful work of Church in his Floral +Mechanisms may be cited as an example. + +It may, of course, be argued that any picture which serves to +illustrate the particular feature is good enough; this is the +contention of one who takes an insufficient pride in his work. A +feature worthy of an illustration deserves the best the author can +produce, more especially as a literary form is still, fortunately, +preserved or, at any rate, aimed at. + +The reason for indifferent illustrations is primarily due to bad +or mediocre drawings, or to their unsuitability for the kind of +reproduction in view. + +With regard to the first point: this lack of draughtsmanship often +obtains; when education entirely replaces mere instruction, it is to +be hoped that all students of science will be trained in the rudiments +of drawing. Meanwhile the difficulty can be partly overcome, as will +be seen later on, by the simple means of drawing on an enlarged scale, +in order that in reproduction reduction can be made. + +The second reason, the onus of which also falls on the authors, is +a lack of knowledge regarding the kind of drawing suitable for the +different modes of reproduction; this is a very important point, for +"technical conditions govern even genius itself." + +Authors, however, are not always to blame; it would appear that even +editors sometimes are wanting in the requisite knowledge, for we have +known straightforward line drawings reproduced by half-tone; in other +cases the paper used is unsuitable for the reproduction and, at other +times, the printers are at fault. + +With a view to remedying, at any rate in part, these deficiencies, a +course of lectures, arranged by the Board of Studies in Botany of the +University of London, was delivered in the Lent term of 1913 in the +Department of Botany of University College, London. + +In gratifying the wish expressed by some that these lectures should +be given a more permanent dress, the author feels that some apology is +necessary, for he can lay no claim to authoritative knowledge of much +of the subject-matter; questions relating to the graphic arts and to +illustrations, however, have always been of interest to him, so that +he has tried various experiments, often with disastrous results, and +thus has gained some experience. + +In these matters the author has benefited much through his association +with Professor F. W. Oliver, who, characteristically, has been ever +ready to discuss these problems with, and to place his knowledge and +experience at the disposal of the author. + +The outline of the ways and means of illustration contained in the +following pages is primarily intended for ordinary working scientists, +not for artists, professional draughtsmen or skilled amateurs. + +The point of view is mainly botanical, primarily because the present +writer is a botanist and also because the requirements of modern +botany in the way of illustrations are more extensive than those of +any other science; the requirements of other sciences, however, have +not been overlooked. With regard to other branches of knowledge, the +principles considered will, it is hoped, prove of some value to the +workers therein. + +The details of technique have been kept as brief as possible; in +fact, sufficient only has been said to indicate the main principles +involved. In the literature cited, to which the author is indebted +particularly for matters relating to technique, will be found full, +and sometimes exhaustive, accounts. + +With regard to the illustrations, these have been selected to +illustrate the various methods of reproduction described or to +demonstrate the points raised. In those instances where the source has +not been acknowledged or the draughtsman or photographer mentioned +by name, the figure is by the author: and since the actual making +of plates and blocks is of considerable importance, the firms, when +known, responsible for their making are mentioned in the Table of +Illustrations. In this connexion the author desires to express his +appreciation of the skill shewn and care taken by Messrs. André, +Sleigh and Anglo, Limited, who prepared the majority of the new +illustrations which appear in the following pages. + +The author is indebted to many who have helped in various ways in the +production of his work; particularly is he desirous of expressing +his warmest thanks to Miss O. Johnston for the charming drawing +of _Geranium columbinum_ (Plate 2) and to Mr. Harry Becker for +his beautiful lithograph (Plate 1). To Miss S. M. Baker, Dr. W. G. +Ridewood, and Miss Winifred Smith thanks are due for the loan of +original drawings; also to Mr. Edward Hunter and Mr. Hugh Hunter for +information regarding matters of technique and cost. + +The number of illustrations would have been less but for the +generosity of Messrs. Chapman and Hall, the Editors of the "Annals +of Botany," "The Imprint," and the "New Phytologist," Professor F. W. +Oliver and Mr. G. N. Oliver in lending blocks. Recognition also must +be made of the kindness of Mr. Richard G. Hatton in consenting to the +use of certain blocks from his admirable "Craftsman's Handbook," +of the Delegates of the Clarendon Press for permission to reproduce +figure 14, and of Messrs. Frederick Warne and Co. for permission to +make use of the wood engraving by Messrs. Edmund Evans, Ltd., of Kate +Greenaway's charming Milkmaid. Finally, the author desires to express +his sincerest thanks to Mr. Gerard T. Meynell, of The Westminster +Press, for the keen interest he has taken in the work, for his help +with the illustrations, and for the great care he has taken in the +production of the book. + + University College, London + _January, 1915._ + + + + +INTAGLIO PRINTING + + +In the biological sciences the massing of illustrations into plates is +still the favourite method of illustration, although text-figures have +recently become more numerous. + +This is partly due to innate conservatism, for most of the earlier +memoirs were so illustrated, doubtless because it saved time, since if +wood engravings were used with a view to text-figures, the compositor +had to wait for the blocks, whereas in the case of plates the +compositor and the engraver worked independently. Also the +possibilities of plates are enormous; they may be very beautiful +indeed besides being biologically satisfactory, for much finer results +can be obtained by engraving metal than by engraving wood. Then again +there are many different processes available for the making of +plates, so that if one proves unsuitable for a subject an excellent +reproduction may be obtained by another. + +Before passing on it is desirable to point out the essential +differences in the three ways of printing. + +_Intaglio printing._ If the finger-tips be examined, many ridges and +furrows will be seen on their under surfaces; if now a thick ink +be well rubbed into these so as to fill well the furrows, and the +superfluous ink be wiped off from the general surface, an impression +will be obtained of the furrows on pressing the fingers on to a piece +of smooth white paper. Better still, if the copper plate of a visiting +card be examined, the name will be found cut into the surface. If an +intimate mixture of tallow and lamp-black be well rubbed into these +depressions and the excess of ink wiped off the surface of the plate, +an impression can be obtained by placing a piece of damp paper on +the plate and passing both through the domestic mangle--the kind with +rubber-covered rollers. In each case the principle is the same, the +pressure forces the paper into the depressions of the plate so that it +takes up the ink. + +_Plane surface printing._ This is characteristic of lithography and +allied processes. Writing or a design well chalked on a blackboard +can be transferred on to a smooth piece of paper merely by a little +vigorous rubbing on the back of the paper placed in position over +the drawing. The transfers of childhood provide a further simple +illustration, so also does the hectograph (jellygraph). + +_Relief printing._ In this case, the design is raised above the +general surface of the substance. A rubber stamp is an obvious +example. + +It will be noticed that intaglio and relief are the reverse one of +the other, whilst plane-surface printing is intermediate between these +extremes. In intaglio, the ink is taken from a depression; in relief +from an elevation; and in flat printing from a plane surface. + + +INTAGLIO PLATES. There are several methods of making intaglio plates, +but only a few are used in the illustration of scientific papers; +attention however may be drawn to the others, not only for their +own sake, but also on account of their influence on some modern +photo-mechanical processes. + + +LINE-ENGRAVING. Line engraving, by which is meant cutting lines into +copper, steel, or other suitable material with a burin or graver, is +a very ancient art. Its employment for illustrative purposes is an +outcome of the art of the metal workers--particularly the Florentine +goldsmiths of the fifteenth century--who filled up the lines cut in +the metal with a black enamel of silver and lead sulphides (niello) +which was made by heating together a mixture of these metals with +sulphur. This enamel when once in was very hard to remove, so that in +order to see how their lines were progressing, the artists rubbed +well into the metal, in order to fill up the lines, a sticky ink. The +superfluous ink was then wiped off the general surface of the metal +and a piece of paper was placed in position and pressed sufficiently +hard to make it enter the depressions, which alone contained the +pigment, and take up the ink. A print was thus obtained of the work +and so its state was ascertained. + +Metal engraving is carried out in the same fashion at the present +time. A flat plate of copper or steel is well polished and is worked +upon with a graver or burin, so that the picture is represented +by lines cut into the metal. Any line, however fine, will give an +impression on printing, hence it is hardly surprising that engraving +has long been a popular means of expression by artists, since force, +depth and delicacy are possible of attainment. + +The printing is carried out in exactly the same way as by the early +metal workers: the plate is covered with a thick ink which is forced +well into the lines and then the superfluous ink is removed. The plate +is now ready for printing; to do this, the plate is placed in the bed +of a copper-plate press and over it is laid a sheet of damped paper +which is covered with two or three layers of blanket. The whole is +then passed under the roller which forces the paper into the incised +lines, so that not only is the ink picked out, but a mould of them +is taken on the paper, hence the very finest lines will give an +impression. Having passed through the press the paper is carefully +peeled off, and thus the print is obtained. + +With regard to the metal employed, copper is commonly used, since +it is soft and easy to work; its softness however is, in a sense, a +disadvantage, since the plate will soon wear, the finest lines being +the first to go, so that a limited edition of good impressions only +is possible. To overcome this difficulty, the plate may be faced with +steel, by which means it is rendered very durable. + +Steel, although once popular, is not much used nowadays owing to its +hardness and the rapidity with which it rusts. As compared with copper +engravings, steel gives a somewhat harder line, whilst copper gives +a soft line, but this, of course, does not mean that steel engravings +are harsh; the finest work can be done on steel and of remarkable +delicacy. + +At the present day line engraving is seldom or never used as a means +of illustrating scientific work. It is obvious that the average +scientist has not the time and he certainly does not possess the skill +to make his own plates; the engraver must translate the originals into +lines, so that much consultation would be necessary. Further, a +line engraving takes a long time to make, and most publishers would +certainly look at the expense. + +In the past, however, the line engraving was much used, and very +beautiful work was often accomplished. The following works contain +outstanding examples. + + Bojanus: _Anatome Testudinis Europaeæ_, Vilnae, 1819-1821. The + plates are beautiful engravings by Lehmann after the drawings + by the author. + + Chatin: _Anatomie Comparée des Végétaux_. Good steel + engravings illustrating the structure of various plants. + + Curtis: _Flora Londinensis_, London, 1777. The illustrations + are hand-coloured copper engravings by Sowerby and others, + many of which, particularly the earlier ones, are of + outstanding excellence. The engraving is often nothing more + than the mere outline of the plant, whilst in cases where the + structures are more massive, a certain amount of shading is + used. The colouring is very good indeed, and it is obvious + that much care was taken not only in the actual painting but + also in the choice of pigments which, as far as can be judged, + are as fresh now as when first used. + + _Curtis's Botanical Magazine_ and _Edwards's Botanical + Register_ contain some excellent examples of hand-coloured + copper engravings. + + Levaillant: _Histoire Naturelle des Oiseaux d'Afrique_. Paris, + 1805-8. This work contains beautifully coloured engravings by + Feesard. The original drawings were by Reinold. + + Lyonet: _Traite Anatomique de la Chenille_. La Haye, 1762. + The plates are amongst the best illustrative of zoological + science. + + Martius: _Flora Brasiliensis_. The earlier volumes, _e.g._, + Vol. 13, Part I, contain excellent engravings. + + Passæus: _Hortus Floridus_. Arnheim, 1614-17. + + Sowerby and Smith: _English Botany_. London, 1790-1866. The + illustrations are hand-coloured copper engravings. + + Thuret et Bornet: _Etudes Phycologiques_. Paris, 1878. This + work contains the finest plates ever published in a botanical + work. Riocreux drew from the preparations, and his drawings + were engraved on steel by Picart, Thomas and others. + + +ETCHING. Etching is a term very loosely used; strictly speaking it +consists in corroding a metal plate or a flat stone with acid, or +other substance possessed of a kindred action, so that depressions are +formed. A pen and ink drawing, although usually so termed, is not an +etching. Briefly the method is this: a well polished copper, steel or +zinc plate is covered with a substance, known as the etching ground, +consisting commonly of a mixture of asphaltum, white wax and pitch, +which resists the action of the acid. The ground may be laid in more +than one way; the simplest, perhaps, is to dissolve the etching ground +in some solvent such as chloroform, which readily volatilises, and to +pour the solution on to the plate, which is tilted this way and that +until the liquid is evenly distributed; the excess is poured off and +what remains is allowed to dry, the plate being kept level during the +process. + +The plate is then warmed until the ground is softened, when it is held +over a smoking candle and is rapidly moved here and there so that if +properly done the fine soot is evenly incorporated in the ground. +When the plate is cold, the drawing may be made by cutting through the +etching ground, so as to expose the underlying copper, with needles of +various sizes. The work is then etched by means of dilute nitric acid. + +When this is satisfactorily accomplished, the ground is cleaned off, +the plate well inked with copperplate ink, and the surface ink removed +by coarse muslin. The plate is then gone over with fine muslin, but +the ink must not be removed from the depressions; finally the damped +paper is placed in position and impressions obtained by the use of the +copper-plate press. + +Etching, although suitable, especially when natural-printed,[A] for +the illustration of many scientific subjects, is but seldom employed +at the present time for this purpose; the preliminary announcement +of Warburg's _Die Pflanzenwelt_, however, states that some of the +illustrations are etchings. + + [Footnote A: A plate is said to be natural-printed when all + the ink is removed except from the depressions; in artificial + printing some ink is allowed to remain on the flat parts. + Artists frequently, after removing the superfluous ink, + lightly dab the plate in order to make the pigment spread + slightly beyond the actual limits of the depressions; this is + known as _retroussage_.] + + +SOFT-GROUND ETCHING. This is a somewhat rare method of reproduction +nowadays; it may, however, be described briefly, for it would appear +to be suitable for scientific purposes, since it should not prove a +matter of great difficulty for an author who is a sufficiently skilled +draughtsman to make his own plates. The polished copper plate is laid +with ordinary ground to which is added lard in a quantity according to +the warmth of the weather. + +Over the plate is then placed a sheet, larger than the plate by an +inch or two, of damp, thin, grained paper, the edges of which are +folded over and pasted to the back of the plate. When the paper is dry +it will be well stretched and in close contact with the plate. With +the hand resting on a bridge, in order to avoid inadvertent touching +of the plate, the drawing is made on the paper with a pencil of a +hardness suited to the softness or otherwise of the etching ground. +When the drawing is finished the paper is carefully removed; wherever +the pencil has been used, the etching ground will adhere to the paper, +so that in such places the metal will be exposed. The plate is then +etched and printed as in the normal process. + +No reproductions of drawings of scientific subjects apparently have +been reproduced by this method. Examples can conveniently be examined +in _The Seven Lamps of Architecture_ by Ruskin. + + +MEZZOTINT. The characteristic feature of mezzotint is that the +subject is translated into tones rather than lines as in the preceding +intaglio methods. + +The surface of a smooth metal plate--usually copper--is raised into +innumerable and minute projections by going over it in all directions +with a curved steel tool, known as a rocker, the edge of which is +finely toothed. An impression taken of the plate in this condition +will give a deep rich tone. The high lights are obtained by scraping +and burnishing away the elevations so that there are no pits left +to hold the ink, and, similarly, intermediate tones are produced by +partly removing the pile so that the pits are made of varying degrees +of shallowness and consequently will print in tones according to their +depth. + +Impressions are taken in the same way as in the case of etchings. + +Mezzotint apparently has never been used for the reproduction of +scientific subjects. Indeed, in a sense, this process is much too +artistic for the purpose. At their best, illustrations reproduced +by this method have mystery and depth and give the imagination +much employ; in a word, they are subjective rather than objective, +qualities unsuited for our purpose. + + +PHOTOGRAVURE. Photogravure may next be considered, for although it +is a photo-mechanical process, it corresponds to mezzotint. Excellent +results may be obtained by its use provided the drawings--usually +executed in monochrome such as sepia--be really good, otherwise they +are hardly worth reproducing by this relatively expensive method.[A] + + [Footnote A: This account refers only to plates made and + printed entirely by hand, not to photogravure for printing on + a rotary machine.] + +Photogravure is particularly suitable for the reproduction of drawings +showing a large amount of detail and made up of a variety of tones +rather than lines or stipple. + +The photographic part of the process is essentially the same as making +a carbon print from a photographic negative. This consists in exposing +under the negative the carbon tissue, which is a mixture of gelatine, +in which is dissolved bichromate of potash, and a suitable pigment. +Such a film of bichromate gelatine is, when dry, sensitive to light. +If no light gains access to it, the gelatine is readily soluble in +warm water; if light acts upon it, the gelatine becomes insoluble in +proportion to the degree of its exposure. Obviously, the pigment will +be retained in varying degrees according to the relative insolubility +of the different parts of the gelatine. + +The carbon tissue having been exposed, is rolled down on a wet sheet +of paper covered with some adhesive and is dried under pressure. The +paper is then soaked in warm water when the basis of the carbon tissue +easily peels off; the picture is developed by laving in warm water, +which will dissolve the gelatine in proportion to its exposure to +the light. The print when dry is remarkably permanent and, from the +picturesque point of view, is infinitely superior to the ordinary +silver print. + +The method of making the photogravure plate is, in outline, as +follows: + +The original drawing is photographed, and it is very important that +the negative should be as perfect as possible. + +From the negative, a positive is made upon transparency carbon tissue +which is mounted upon a sheet of plate glass. The procedure is, in +essentials, exactly the same as described above for the making of a +carbon print. This positive when dry may be touched up; after which +a negative, which also may be touched up, is made from it upon an +ordinary sheet of carbon tissue. + +The negative so obtained is transferred to a prepared plate of copper, +developed with warm water and dried. + +The copper plate is prepared as follows: after being well polished +until quite free from all scratches, the surface is dusted over with +finely powdered resin or, more usually, bitumen. The plate is then +heated until the dust adheres. + +After the carbon negative has been stuck on to the plate, developed +and dried, the margins and back of the copper are protected with an +acid-resisting varnish. When dry, the plate is placed in the etching +bath of nitric acid or, more generally, of ferric chloride. The +etching fluid will pass through the thinnest parts of the negative +first, so that the surface of the copper will be etched to a degree +corresponding to the thickness of the gelatine. The high lights on the +negative obviously will be represented by thick coatings of gelatine, +consequently such parts will be but slightly etched and vice versâ. + +If the plate had not been laid with resin, the surface after etching +would show more or less extensive depressions and elevations; but the +grains of resin protect the copper immediately beneath them from the +action of the acid, which consequently can only dissolve the exposed +parts of the metal between the resinous particles. The result is, +therefore, that the plate is covered over with numberless fine pits of +varying depths. The deepest ones will, on printing, give the darkest +tones, since they will hold more ink, the shallower ones will give +the lighter tones, whilst the shallowest and those parts unetched will +give the high lights. + +The plate is usually etched three or four times successively in +varying strengths of fluid, after which the etching ground and +gelatine is cleaned off. + +A strong copper-plate ink is then well rubbed in by means of a dabber, +after which the ink from the surface is removed, first with a coarse +piece of muslin and finally, with fine muslin. The ink must not be +removed from the pits. + +The first pull is then taken as in a line engraving with a +copper-plate press, and its appearance shows what corrections are +necessary. The plate nearly always requires a certain amount of +engraving; the high lights may be improved by means of a burnisher, +the shadows by means of a rocker or a roulette--a small steel wheel +the rim of which is beset with fine teeth--and so on. Finally, if a +large edition is required, the plate is steel faced. + +Although much used for the reproduction of pictures, photogravure is +too rarely employed for scientific purposes; this is to be regretted, +for the process is admirably suited to the reproduction of photographs +and drawings with delicate tones. As compared with the usual +half-tone, the cost is high, and this no doubt militates against its +use. + +Examples of outstanding excellence will be found in the _New +Phytologist_, Vol. xi, 1912, plates 5 and 6. These are absolute +facsimiles of the original drawings by Mr. McLean, both as regards +colour and reproduction of tones. Plate 8 may also be examined and +compared with plates 9 and 10 which are reproductions of the same +subject in collotype and half-tone respectively. + + + + +PLANE SURFACE PRINTING + +[Illustration: PLATE 1.--An original lithograph by Mr. Harry Becker.] + + + + +PLANE SURFACE PRINTING + + +LITHOGRAPHY. Of these methods of printing, lithography is the +outstanding example: it is a method of reproduction possessed of great +possibilities, for by its employment a facsimile of any drawing can be +obtained. + +As a means of artistic expression it ranks high amongst the graphic +arts, and, for the reproduction of drawings of a scientific nature, it +is very popular, since it meets most requirements and is comparatively +inexpensive. + +The art, which was discovered by Senefelder towards the end of the +eighteenth century, depends on the fact that grease and water are +immiscible: a drawing made with a greasy pigment upon a suitable +surface adheres very strongly, whilst those parts free from it retain +water, so that when damped and rolled up (_i.e._, inked), the ink used +will stick only to the lines, etc., of the drawing, but not to the +other parts. + +Clearly the surface is all important, and this is provided by +lithographic stone, a limestone occurring in Germany, France, England +and Canada. The best stones occur at Solenhofen near Munich, those +from other localities being inferior in quality. Incidentally it may +be mentioned that zinc and aluminium plates are not infrequently used +in place of stone. + +Lithographic stones vary in hardness, colour and grain. For the best +work the stone should be homogeneous and of a hardness suitable for +the subject; the colour affords an indication of the hardness, the +lighter-coloured stones, which are much the commoner, being softer +than the darker. + +There are two modes of procedure; the drawing may be made direct on +the stone with lithographic ink or crayon--both being mixtures of +tallow, wax, soap and shellac, with a sufficiency of pigment to render +the drawing visible to the artist--or else the drawing may be made +upon transfer paper. + +The former method, although the more satisfactory and often used +by artists, is seldom pursued in scientific drawings except when +professional draughtsmen are employed. In such cases it may be +necessary to reverse the drawing, which is conveniently done by +viewing it in a mirror, and, of course, all lettering must be +reversed. + +The majority of amateur draughtsmen make their drawings in pencil or +ink and these the lithographer traces upon lithographic transfer paper +and transfers them to the stone; he, the lithographer, may merely +trace the salient features and work the drawing up on the stone. The +transfer papers are coated with gelatine, starch or gum, or mixtures +of these substances, the idea being to interpose between the real +paper and the pigment--in the form of lithographic crayon or ink--some +substance soluble in water which will hold the pigment and prevent +it soaking into the paper, so that a transfer has only to be damped +through the back, pressed on to the stone and peeled off. The work, +together with more or less of the film, will thus be transferred on to +the stone and, of course, will be reversed, since the part uppermost +on the stone will be the back of the original drawing. + +The original drawings may be made upon the transfer paper direct, and +in so doing mistakes in tracing will be obviated. Suitable papers are +made for various purposes, e.g., smooth for ink work and variously +granulated for crayon (see Plate 1, which was drawn by Mr. Harry +Becker on transfer paper). + +Another advantage in drawing directly upon the transfer paper is that +the draughtsman can make corrections pretty easily for, if needs be, +a bad piece of work can be entirely cut out and a fresh piece of paper +inserted. + +Assuming that the transfer method has been employed, the stone must be +prepared according as the drawing is made with ink or with crayon. + +The stone is first thoroughly ground, in order to rid it of all traces +of previous work, and then polished for ink work or grained--_i.e._ +roughened--for crayon work, the small points produced taking up the +crayon in proportion to the amount present on the transfer and the +pressure used. + +The transfer is then damped with water, sometimes with a dilute +solution of nitric acid, and placed in position on the stone, which +is then passed two or three times through the lithographic press until +dry. Then the back of the paper is damped and the sheet peeled off. + +The stone is next proved, _i.e._, prepared for printing. + +It is first carefully examined for broken lines and other blemishes, +which are touched up with ink or crayon. The stone is then painted +over with a solution of gum in water which is allowed to dry, it is +then washed in water and rolled up with ink. The drawing will now be +clearly visible, for if properly inked the clear parts of the stone +will not take the pigment, so that any parts which require cleaning +up may be deleted. This is accomplished by means of a pencil of snake +stone, a piece of pumice stone, an acid stump--a rod of hard wood, the +sharpened end of which is dipped into nitric acid--or with a scraper. +The stone is again washed and rolled up strongly with ink and etched +with a dilute solution of nitric acid which is applied with a sponge; +then the surface is again gummed and the stone allowed to dry. It is +sometimes necessary to re-etch the stone; if so, the damp stone is +rolled up with thin ink and allowed to dry, it is then dusted over +with finely powdered resin, the superfluous resin is removed by means +of a wet sponge, and the surface is painted over with a solution +of gum arabic mixed with dilute nitric acid. If the resin is well +incorporated with the ink, the work will suffer no damage in the +process. The acid gum is then dabbed off with a rag, the stone is +cleaned up with turpentine, rolled up once more, gummed and finally +set aside to dry. + +All this appears complicated, but it is very necessary to get a good +surface for printing. The action of the gum does not appear to be +clearly understood, the nitric acid obviously will etch the stone, so +that the gum will easily penetrate. It is sometimes supposed that the +arabic acid of the gum enters into a chemical composition with the +calcium carbonate, making a film which is the real ink-resisting +surface. This film has not a long life, so that in printing it is +necessary to renew it periodically by the application of gum solution. + +If possible, the stone should be allowed to rest for a day or two +after proving, in order that the ink may sink well in. + +Before printing, the gum is washed off and the stone allowed to +remain in the press-room until its temperature is the same as its +surroundings. The stone is then thoroughly and evenly damped all over, +placed in the press, and rolled up with lithographic ink; the paper +is then laid on, and the whole passed through the lithographic press. +After the first few pulls it will be seen whether all is well. The +essentials of a good impression are these: the lines must be black and +not grey, provided black ink is used; the lines must not be wider or +blacker ("smutty") than those on the stone, nor must they be ragged or +broken ("rotten"). + +In printing, the stone must be damped and inked before each impression +is taken, and occasionally re-gumming is required. Good printing +requires a considerable amount of ability, especially in the case of +crayon drawings. + +The paper used is a very important matter, the selection of which can +be safely left to the lithographer, provided he be a good one, unless +the author possesses the necessary technical knowledge. If a smooth +paper is required, and the paper is not to be damped before printing, +India paper is best and plate paper next best. All coarse or grained +papers must be damped before printing. + +As has already been remarked, lithography is a good process for +scientific work; but, unfortunately, considering the number of +lithographic plates published, really first-class examples are rare. +This is largely due to the original draughtsman; it is unreasonable to +expect a lithographer, in all probability ignorant of the subject of +the plate, to turn out first-class reproductions of drawings which are +obviously bad. On the other hand, lithographers vary greatly in their +capabilities, and indifferent plates may be entirely due to their +ability not being first rate. + +As drawings have to be traced, mistakes are apt to occur; the proofs +should, therefore, be carefully examined, for a certain amount of +correction can be made on the stone. + +The following works contain excellent lithographs, which should be +studied by those interested in the subject. + + Bornet et Thuret: _Notes Algologiques_. Paris, 1876-1880. This + contains some of the best work, illustrative of science, known + to the present author. The original drawings mostly were + made by Bornet, and the lithography was carried out by + Riocreux--one of the best if not the greatest of botanical + artists--Arnoul, Picart and Pierre. + + Davis and Thurnam: _Crania Britannica_. London, 1865. + + Mirbel: _Sur le Cambium_, Paris, 1842. The plates provide + excellent examples of ink lithography by Laplante. + + Von Mohl: _Schriften botanischen Inhalts_. Tübingen, 1845. + Good examples by Federer. + +The first volumes of the _Annales des Sciences Naturelles_ (Paris) may +be referred to for lithographic work earlier than the above (1820). + +For more modern examples the following may be consulted: + + Blackman and Welsford: _Fertilisation in Lilium_, Annals of + Botany, Vol. 27, 1913. + + Gravis: _Recherches anatomiques sur les organes végétatifs de + l'Urtica Dioica_, Bruxelles, 1885. This memoir contains both + good and indifferent plates. + + Keibel: _Normentafeln zu Entwicklungsgeschichte der + Wirbeltiere_, Jena, 1904. + + Reed: _A Study of the Enzyme-secreting Cells in the Seedlings + of Zea Mais and Ph[oe]nix dactylifera_. Annals of Botany, Vol. + 18, 1904. + + Semon: _Zoologische Forschungsreisen in Australien_, Jena, + 1904. + + Vaizey: _On the Morphology of the Sporophyte of Splachnum + luteum_, Annals of Botany, Vol. 5, 1890. + + Woodburn: _Spermatogenesis in Blasia pusilla_, Annals of + Botany, Vol. 27, 1913. + +Several memoirs in the _Fauna und Flora des Golfes von Neapel_ +(Berlin) are illustrated by excellent lithographic plates. Many good +examples of chromolithography also will be found there. + + +CHROMOLITHOGRAPHY. Lithography is much used for the reproduction +of coloured pictures and illustrations, the process being termed +chromolithography. The principles involved are the same as for +ordinary work, but it is necessary to print from several stones, one +for each colour. It is obvious that much skill is required, for the +employment of different colours will give a large number of secondary +and tertiary tints when printed one above the other in various +combinations. Thus, by printing part of a design in yellow and +the other part in blue, the finished product would show three +colours--yellow, green and blue, and by the use of three primary +colours a large number of different tints may be obtained. + +As already mentioned, each colour is printed by a separate stone, +there is thus no limit--excepting that of expense--to the number of +different colours which can be obtained. + +In practice it is usual to make an outline of the essential parts +of the composition on a stone, known as the keystone, which is not +necessarily used in printing the picture. An impression of this +outline is taken upon a sheet of paper, which is used to transfer the +design on to the stones, on each of which the artist will draw only +those parts which he desires to be printed in one particular pigment. + +Although the sequence of colours is generally blue, red and yellow, it +is obvious that various changes in this order must be made according +to the colours used and the exact tint required. For instance, a +body colour such as cadmium yellow would precede a glaze such as +madder-lake; again, two distinct tints may be obtained from red and +blue, for example, according to the order of printing--red upon blue +will give a mauve, whilst blue upon red will give a purple. + +A knowledge of pigments is thus all important, and in printing, the +superposition must be perfect. + +Plate 2 is an example of a chromolithograph. Miss O. Johnston first +drew the outline of the plant, which was phototransferred on to the +stone. An impression was then pulled and tinted by the artist, +and from this tinted impression the colour stones were made by the +lithographer. It may be added that only three colours were used in +printing the plate. + +Examples: + + Baur: _Einführung in die experimentelle Vererbungslehre_ + (Plate 1). Berlin, 1911. + + Bruce and others: _A Note on the Occurrence of a Trypanosome + in the African Elephant_. Proceedings of the Royal Society of + London, B. Vol. 81, 1909. + + Cropper: _The Development of a Parasite of Earthworms_. _Id._ + Vol. 85, 1912. + + Oliver: _On Sarcodes sanguinea_. Annals of Botany, Vol. 4, + 1889-1891. + + Rubbel: _UEber Perlen_ ... Zoologische Jahrbuecher, Vol. 32, + 1911-12. + + Biometrika, 1906-7, Vol. 5, Plate 23. + +Mention has been made of the value of a knowledge of colours. The +subject is much too extensive to be considered adequately on the +present occasion even if it were desirable; its importance, however, +warrants a few passing remarks.[A] + + [Footnote A: See Ridgway: _Color Standards and Color + Nomenclature_.] + +No two people will describe in the same way the colour of, say, a rose +petal; both will have a different conception of the colour "crimson." +The majority have but a limited sense of colour, and even when this +faculty is possessed, the personal equation looms large; further, +the ordinary names of colours are quite inadequate for descriptive +purposes. For these reasons the importance of a scientific system of +colour nomenclature and colour standards is all important. By the +use of such a scheme, the exact colour of an object can be found +by comparison with an adequate chart, and the name there given will +convey to others exactly what colour is described or desired. The +plumage of a bird or the colour of a flower can thus be described +correctly, and an author can indicate exactly the colour desired in +certain parts of a chromolithograph or other reproduction in colour. + + +[Illustration: PLATE 2.--GERANIUM COLUMBINUM. + +A chromolithographic reproduction of a drawing by Miss O. Johnston] + +PHOTOLITHOGRAPHIC PROCESSES.--Of these methods of reproduction there +are several, their value lying in the fact that the originals can be +reduced or enlarged with the greatest of ease. The general principles +are as follows. + +A photographic negative is taken of the original drawing and a +positive made on a film of bichromate gelatine. Wherever light reaches +the film, the gelatine is rendered more or less insoluble according to +the intensity of the light acting upon it; through the dark parts of +the negative but little light will pass, so that the gelatine will +remain soluble. + +The exposure of the positive having been made, the film, which may be +mounted on paper, is inked with lithographic ink in the dark room and +then washed. The pigment will adhere to those parts acted on by light, +but will wash away from those regions unacted upon; obviously the +half-tones will retain ink in direct proportion to their density. + +The developed positive is then transferred to a stone or zinc plate +and impressions taken as in pure lithography for the dark parts are +resistant to water and will take the ink, whilst the high lights will +retain water and so will not be inked. The intermediate tones will +take the pigment according to their density. + +In distinction to the previous methods, corrections cannot be made +except in so far as the negative can be touched up. + + +COLLOTYPE.--Of the various photolithographic methods which have from +time to time been employed, collotype is the one in most general use +at the present time, especially for the reproduction of photographs. + +Collotype is a simple process which does not require so extensive a +technical knowledge and ability as some of those previously described. +But notwithstanding this, the results are sometimes unsatisfactory +and unequal; faults due to indifferent originals and to unsatisfactory +conditions obtaining in the work rooms. The great drawbacks to good +collotype are cold and dampness, and it is for these reasons that +continental firms, blessed with a more stable climate, often produce +much the best work. Provided the workshops are properly heated, the +collotypers of this country ought to be able to turn out good work at +all times of the year; indeed, the best firms do. + +For this and for other processes in which photographs form the +originals to be reproduced, authors should send the negative to the +collotyper; if this be impossible, positives of the best possible +quality, printed on ordinary P.O.P. paper, toned to various shades +of purple, and also on smooth bromide paper, in ordinary black tones, +should be provided in order that the collotyper can choose the print +he most prefers to work with. Also, it is usual to glaze the prints. + +The method is as follows. A piece of british plate glass, about +half-an-inch in thickness, is ground on one side with fine emery +powder, and then thoroughly washed and dried. The plate is covered +with a filtered mixture of the colloids sodium silicate and dextrine +or albumin, and placed in a warm oven to dry. If metal plates are +used, such as zinc or copper, this preliminary coating is unnecessary; +glass plates, however, must have the substratum in order that the +sensitised gelatine--which is next put on--may stick. + +When the plate is dry, it is thoroughly washed with water in order to +remove any free silicate; it is then dried and put away until required +for use. + +The sensitising solution is made up of gelatine and bichromate of +potash dissolved in water; before use it is filtered, freed from air +bubbles and heated to not more than 120° F. The plate is now placed +on a stand, which is provided with levelling screws, in the oven, and, +when the temperature has reached 120° F., an amount of the bichromate +gelatine solution sufficient to make a thickness of film proper for +the mode of printing to be employed is poured upon the plate. + +The oven is kept at a constant temperature, 120° F., until the +gelatine is dry, when it is allowed to cool gradually. + +Whilst the gelatine is setting, precautions against vibration must be +taken else the plate will be spoilt. + +When dry, the collotype plate is sensitive to light and moisture; +its surface shows a more or less regular series of convolutions which +resemble those of the outer surface of the human brain, although, +of course, very much smaller. The character of the grain is very +important, for if it be too fine it will not take up a sufficiency +of ink, and, on the other hand, if too coarse it will yield coarse +impressions. + +A reversed negative, of a quality beyond reproach, must be made of the +original; if the subject is dark or has heavy shadows the negative is +frequently slightly over exposed so as to soften them. + +The collotype plate is then exposed under the negative and washed in +cold water until the yellow bichromate no longer comes away. It is +then dried. + +In printing, the plate is damped and rolled up with ink as in +lithographic printing; the amount of ink adhering to the film depends +on the extent to which the different parts have been acted on by +the light, as has already been mentioned. The moistening of the +plate--mis-termed etching--is best done with dilute glycerine +containing 75 per cent. of water, which when first applied should be +allowed to remain on for about half-an-hour. The excess of moisture is +taken up with a sponge or a ball of rag, and then the plate is inked +and printed in a lithographic or a collotype press. The picture is +usually masked with tin foil in order that its edges may be quite +clean. + +Of the faults which may occur, the following may be alluded to. A +mottled appearance may obtain in the high lights; this is due to the +coating of gelatine being too thick. More commonly, the reproductions +may appear flat owing to the degradation of the high lights; this is +a sign that the sensitive film has been acted upon by moisture during +its critical existence between the drying and the washing out of the +potassium bichromate, or that the temperature has been too low. + +The following contain good examples of collotype. + + Karsten and Schenck: _Vegetationsbilder_, Jena. + + Oliver: _Notes on Trigonocarpus and Polylophospermum_. New + Phytologist, Vol. 3, 1904. + + Semon: _Zoologische Forschungsreisen in Australien_. Jena. + 1912. + + Thompson: _The Anatomy and Relationships of the Gnetales_. + Annals of Botany, Vol. 26, 1912. + + See also Plates 3, 4, 5 and 9 in the present work. + + +THE PREPARATION OF ILLUSTRATED PAGES. Of the processes dealt with, +photogravure lithography and collotype are those most generally used +at the present day for the printing of plates or insets. Half-tone +also is employed, a process which will be considered later since it +is essentially relief printing. This, therefore, is a convenient +opportunity to make a few general observations on plates. + +Plates should only be employed for the reproduction of subjects of +such complexity that cannot be reproduced satisfactorily by figures in +the text. + +A plate or page made up of several illustrations should look well as +a whole; in other words, it should not outrage all the canons of +composition, it should have some pictorial effect. At the same time, +for facility of reference, the individual figures should run in a +convenient sequence. This latter point is so important that a plate +composed really well is distinctly rare, for a compromise nearly +always has to be made. At the same time there are, apparently, +comparatively few authors who pay much attention to plate design. + +Although it is not desired to write of the laws of pictorial +composition, attention may be drawn to a few points which are amongst +those generally neglected. + +The figures should not be crowded together; a reasonable amount of +margin should be left around each. They should be arranged, as far as +possible, in such a way that a sense of balance is maintained. As +to how this is to be accomplished will depend upon the nature of the +illustrations; if they are all about equal in tone, the largest ones +should preponderate towards the base of the plate, and not _vice +versâ_. The difference which this makes will be obvious if the two +accompanying illustrations (Figs. 1 and 2, Plate 3) be compared. The +first is a reduced copy of the plate as it was published: it will be +noticed that it has a top-heavy appearance, which is corrected in the +second figure by the simple device of turning it upside down. + +[Illustration: PLATE 3.] + +If, on the other hand, the figures are some lighter and others darker, +the latter should form the base, since low tones give the idea of +solidity; this is so marked that in cases where the figures vary much +in size and tone, the darker ones may nearly always be situated at the +base or at any rate low down on the plate unless they are very much +smaller than the lighter toned ones.[A] + + [Footnote A: If, of course, the reader understands + chiaroscuro, he will take no notice of this paragraph, but + arrange his plates in accordance with his ability.] + +An examination of the figures on Plates 4 and 5 will roughly +illustrate these points. The upper figure of Plate 4 is well designed, +and no improvement could be made, bearing in mind the compromise +alluded to above. The lower figure is, however, not so good, it was +obviously a difficult one to arrange; it would have been improved if +Figs. 23, 26 and 28 could have been placed in the top tier, but this +would have seriously disturbed the sequence. The first illustration +on Plate 5 is well designed; it would, however, have been improved by +interchanging 8A and 11B. + +[Illustration: PLATE 4.] + +[Illustration: PLATE 5.] + +We may now pass on to the individual figures; these should shew the +essential features, together with some surrounding and comparatively +extraneous matter; often there is included too much of unimportance +and its retention means a waste of valuable space. The first thing to +do, therefore, is to trim, if needs be, the figures; their shape is +more or less immaterial, provided that in cases where there are a +large number of illustrations on one plate, they are not all alike. +The American fashion of circular figures is particularly displeasing, +at any rate to the author. + +Having trimmed the figures, the next point to decide is whether any +require reduction; if they do, cut out pieces of paper (referred to as +patterns below) of the size which the figures will ultimately appear: +on the whole, it is better to avoid reduction of the originals, +for without a good deal of experience it is very difficult to judge +exactly what the result will be; a good idea, however, may be gained +by the use of a diminishing glass. + +The size of the available surface of the plate should now be ruled +on a white sheet of fairly thick cardboard, and the figures, or their +patterns, arranged so as to be easy of reference, to compose as well +as may be, and spaced in such a way that, in the case of a quarto +plate to be folded vertically, no figure is placed so that the fold +will pass through its centre. Nothing is more irritating than having +an illustration spoilt in this way. + +All this may be done by arranging in different ways until a +satisfactory result is obtained, a process which may take an hour +or two. The figures should then be pasted down, covered with several +sheets of blotting paper and placed in a press. A press is seldom +available; when such is the case, a number of heavy books serve +equally well. + +The lettering must next be attended to. The individual figures are +usually designated by numbers; this is a bad method, since it involves +referring to the description of the plate. The best way is to use a +number, and after it to add the name of the plant or animal, and, if +needs be, a description as short as may be. If the author can "print" +or write reasonably well, well and good; if not, it is better to +attach a slip to the plate with full directions relating to lettering, +and to write in pencil on the plate the titles, etc., required in the +proper places for the guidance of the craftsman. The typewriter is +sometimes employed for this purpose by authors; it is purely a matter +of taste, but some readers feel a slight shock when this method is +resorted to. + +In some cases a key to the plate printed on tough translucent tissue +paper and having the necessary information, guide lines, etc., is +inserted with the plate.[A] + + [Footnote A: See Kerner and Oliver: _Natural History of + Plants_ (First Edition) London, 1894.] + +In the case of glossy chromolithographs this practice is best avoided, +for the key is apt to stick to the plate if too much pressure is used +when the book is bound. + +With regard to the "catch letters" used to indicate different parts: +these should be as obvious as possible, and the guide lines should be +either in black or in white ink, according to the general tone of the +illustration. These lines should be conspicuous without being heavy. +Not infrequently they, together with the lettering, are printed on the +plate by a second impression in red ink. + +The foregoing is primarily the business of the author; with regard to +editors and publishers, all plates should be mounted in a manner to +facilitate reference and should be printed on suitable paper; the +former is seldom or never done. All plates which must be constantly +referred to in reading the text should have a selvedge as broad as the +book, so that when unfolded the whole plate is visible, no matter what +page is being read. This would, no doubt, prove an additional expense, +but this should not militate against the suggestion here made, not by +any means an innovation, for in many cases it would save the expense +of mounting on guards, and, further, the additional expenditure could +be saved several times over in other ways. + +With regard to paper, this generally is satisfactory; unfortunately, +highly glazed paper, mis-termed art paper, with an enamelled or chromo +surface, and consisting chiefly of china clay and size, is generally +used for printing the best half-tone reproductions. For this purpose +a paper with a suitable surface, obtained by means other than those +mentioned and not too costly, is highly desirable, since art paper has +the reputation of being not at all permanent, owing to the deleterious +action of moisture, and is somewhat brittle. When used, art paper, if +folded, should have a proper paper hinge along the fold. + +Half-tones are occasionally printed on a kind of vegetable parchment, +a paper which should be more extensively used since it will sometimes, +but not always, give as good a reproduction as art paper, and the +final result is more pleasing from the artistic point of view. + +[Illustration: G. Oliver, del.] + + + + +RELIEF PRINTING + +[Illustration: + + Little maid, little maid, + Whither goest thou? + Down in the meadow + To milk my cow. + +Fig. 1.--A wood engraving, by Edmund Evans, from the original drawing +by Kate Greenaway. + +Reproduced by permission of the publishers, Fredk. Warne & Co.] + + + + +RELIEF PRINTING + + +In order that illustrations may be incorporated in the text, the +blocks used must be in relief the same as the type; a mixture of +intaglio and relief is impossible, for the whole surface must be level +in order to be inked by the rollers, which deposit the pigment evenly, +so that only one tone of colour--that of the ink--is possible. + +Up to quite recent times wood cuts and engravings were the only means +available for text-illustrations, so that this method may next be +considered.[A] + + [Footnote A: See Treviranus, C.L.: _Die Anwendung des + Holtzschnitts zur bildlichen Darstellung von Pflanzen_. + Leipzig, 1855.] + +WOOD CUTS AND ENGRAVINGS. The invention of illustrating by means of +wood blocks followed closely on the heels of the use of moveable types +for printing. The Chinese were the first, as far as is known, to use +these methods of printing and illustration; in the western world the +first wood blocks date from the beginning of the fifteenth century. + +All the earlier cuts were made, commonly on pear wood, on the +longitudinal face of the wood, in technical language "on the plank," +and seemingly, in many instances, were made from drawings in ink. By +cutting on the plank, the craftsmen were enabled to make large blocks, +but were prohibited from doing anything more than relatively simple +and straightforward work. Such blocks are known as wood cuts; wood +engravings were not made until the possibilities of a hard wood like +box carved upon the transverse section were discovered at a much later +date. This is, strictly speaking, wood engraving, an art which almost +entirely, if not quite, superseded the older craft, on account of its +great possibilities; indeed, wood engravers imitated metal engraving +so closely as to deceive many. But such work was enormously laborious; +for instance, in the case of a fishing net, if the string were to be +printed black, the engraver would have to cut out hundreds of small +diamond-shaped pieces of wood in order that the string of the net +should be in relief. But few artists would do this of their own +free will, and generally such laborious work will only be found +in wood-engravings which were intended for the reproduction of ink +drawings or other kinds of pictures where the lines, shading, etc., +had to be faithfully copied. This point may be illustrated by the +accompanying cut (Fig. 2), which was made by my friend Mr. Geoffrey +Oliver, who at the time was totally uninstructed in the art and +knew nothing of its literature. It will be seen that he, quite +unconsciously, treated his wood in the same way as an engraver would +his metal; the result, of course, is just the opposite to metal +engraving since the printing of the wood block is the reverse to +intaglio. + +[Illustration: Fig. 2.] + +In fact, the cut illustrates the three fundamentals of wood engraving; +the white line made by cutting out the wood so that no impression will +be obtained when printed; the white space which is similarly obtained; +and the black space, which is made by leaving the wood untouched. It +was, however, necessary to employ the black line, otherwise the tape +with which the two men--the artist and his father--are measuring the +trunk of the tree would be invisible where it crosses the sky. In a +word, the little picture illustrates very nicely the legitimate use of +wood in the graphic arts. + +As already remarked, the majority of the earlier wood cuts and +engravings are reproductions of line drawings, so that although we may +admire and often marvel at the technical ability of the engraver, the +credit for what artistic merit such illustrations may possess must, in +the majority of cases, go to the draughtsman. + +The work of the earlier wood engravers may be conveniently studied in +_A Lyttel Booke of Nonsense_, by R. D., London, 1912. (See also the +relevant works cited under Literature, p. 94). + +Bewick, of course, is an outstanding example of an artist who used +wood engraving for illustrating natural history; the methods he +pursued may be studied in the tailpiece on p. 11, which was printed +from an electrotype of the original block. + +Wood engraving, up to quite recent times, was the method of +reproducing text figures; not only for scientific books and +periodicals, but also for general literature and journals. + +Much of this work is of outstanding excellence; for scientific work +the following may be studied: + + Duchartre: _Eléments de Botanique_. Paris, 1867. The drawings + were made by Riocreux and engraved by Leblanc. + + Baillon: _Histoire des Plantes_, Paris, 1887. This work + contains some beautiful wood engravings, reproductions of + drawings by Faguet. + + Bentham: _Handbook of the British Flora_, London, 1865. The + engravings are from drawings by W. H. Fitch. + + Deschanel: _Natural Philosophy_, London, 1890. The engravings, + many of which are of excellent quality, are by Laplante, + Rapine and others. In many cases, notably in the + representation of the rays of light passing through lenses + and also in the illustrations of snow crystals, the use of the + white line is admirably demonstrated. + + Kerner: _Pflanzenleben_, Leipzig, 1888. This contains some + excellent engravings by Winkler and others. + + Le Maout et Decaisne; _Traité général de Botanique_, Paris, + 1876. This work contains splendid examples by Riocreux and + Steinheil (see Fig. 8). + + Oliver: _First Book of Indian Botany_, London, 1869. This + contains some characteristic work of W. H. Fitch. + +It does not appear to be generally known that excellent reproductions +in colour may be obtained from wood blocks by superposed printing in +a manner comparable to that followed in chromolithography although, of +course, in the present instance, the blocks are in relief (Fig. 1). + +From the foregoing account it is obvious that the engraving even of +a small illustration, except it be in mere outline, involves a +considerable amount of labour; in fact, if the subject were large +it was usual to cut it up into areas and distribute between several +engravers, the finished blocks finally being joined together to make +the block of the whole picture. Hence it is not surprising to find +that when the photo-mechanical processes were perfected, the older +methods of reproduction were ousted by the newer, more especially +since they are much less expensive; these, therefore, may next be +considered. + + +THE HALF TONE PROCESS.--For the making of a relief block by +photo-mechanical means, the main difficulty is the proper rendition of +the tones intermediate between black and white; this has been solved, +at any rate in part, by the discovery of the half-tone process. + +If an ordinary photographic negative be highly magnified, it will be +seen that the high lights, the low lights, and the intermediate tones +are made by the varying density of the reduced silver. In the lighter +parts the small black particles are surrounded by colourless areas, +whilst in the dark regions small colourless patches are surrounded by +black areas owing to the closeness of the particles of silver (Plate +5, Fig. 2). + +What is required, therefore, is a relief block which will print +a number of dots of equal density but of unequal size. Vervasser +illustrates the point in an ingenious way: a plate, covered with a +number of cones, is supposed to be acted upon by light in such a way +that the cones are truncated in varying degrees according to intensity +of the light falling upon them. The section of such a plate would +therefore shew a curve (Fig. 3); now if the truncated cones be brought +down to one level and a print taken from them, the high lights would +be represented by black dots surrounded by white areas and so on. + +[Illustration: Fig. 3] + +This illustrates the principle which obtains in the making of +half-tones in which the image is made up of a large number of dots +varying in size but all equally dense, so that when viewed from a +suitable distance the dots are individually invisible but compose +to give gradations of light and shade. In other words, the structure +obtaining in a photographic negative is, in a sense, realised by +optical chemical means, although the dots in a half-tone block are +much coarser than those in a negative (Plate 5, Fig. 3). + +This result is obtained by interposing between the diaphragm of +the camera and the negative--for the half-tone process is a +photo-mechanical one--a glass screen covered with intersecting +engraved lines (Fig. 4). As a matter of fact, each screen consists of +two plates of glass similarly ruled and cemented face to face so that +the lines intersect. + +[Illustration: Fig. 4] + +It may at first be thought that the effect of such a screen placed in +front of the negative would be to produce merely a cross hatching on +the reproduction; this, however, is not the case; if the screen be +placed in a proper position relative to the negative and the size +of the diaphragm of the camera, the picture will be reproduced in a +series of dots of varying size. + +The optical and other reasons for this phenomenon must be sought +elsewhere,[A] but the following brief consideration will serve to +illustrate what happens. The rays of light which ultimately reach the +sensitive plate are acted upon by two lenses, that of the camera and +the meshes of the screen, each one of which acts as a lens on the +principle of the pin-hole camera. Each mesh, therefore, brings the +image of the diaphragm to a focus on the negative, but the lens of +the camera focusses the picture as a whole, thus the amount of light +falling on the different pin-holes will vary in intensity, and hence +the dots produced will vary in size, for it is assumed, with good +reason, that each dot is built up from its centre and radially expands +according to the amount of light acting upon it. + + [Footnote A: See Verfasser, _loc. cit._, p. 94.] + +It is obvious that the quality of the resulting picture will depend, +other things being equal, upon the coarseness of the screen employed. +Screens are ruled with lines varying from 50 to 400 to the inch: the +lower rulings give very coarse reproductions, and are only used for +posters, whilst the higher rulings yield very fine impressions and are +employed only for the best work. It is hardly necessary to remark that +the finer the screen the better must be the skill of the printer. +To illustrate the difference in the results obtained by the use of +different screens, the two figures on Plate 6 have been prepared; both +were made from the same negative, but for the upper figure a 100-line +screen was used, and for the lower a 200-line screen. It will be +observed that there is more contrast in the former, and more detail +in the latter. Authors should therefore mention when sending in their +original pictures the qualities they require in the reproduction; it +must, however, be remembered that the blocks made from the finer ruled +screens will not print satisfactorily except on more or less highly +glazed paper, to the use of the "art" varieties of which there are +objections on æsthetic and other grounds. + +[Illustration: PLATE 6. Half Tone reproduction of a photograph by Mr. +W. Rowan. + +Part of a shingle beach shewing plants of Sea Blite (_Suaeda +fruticosa_) and a ring plover's nest with four eggs.] + +Before passing on it may be mentioned that screens with patterns other +than that represented in Fig. 4 are sometimes employed; for instance, +the wavy-line screen gives the impression of coarse collotype. + +The preparation of the blocks may now be briefly dealt with. + +A negative of the picture, using a screen suitable for the purpose, +is taken on a special dry gelatine plate ("process" plates) or on some +other form of negative, _e.g._, wet collodion which is most commonly +employed. This negative requires very careful development in order to +get the dots right. + +From the negative a positive is made upon a copper or zinc plate, +suitably coated with a sensitive film. The usual practice is to coat +the polished metal plate with a mixture of water, albumen, fish glue, +ammonium bichromate, chromic acid and ammonia; the plate is then dried +and, when cooled, exposed under the negative. The action of the light +on such a film, the essentials of which are the albumen, the glue +or gelatine and a chromate, has already been described. The mixture +becomes more or less insoluble in water, according to the intensity of +the light falling upon it. + +The positive is now rinsed in water, and is sometimes stained with +an aniline dye in order to render the film more visible. Next it +is developed in a stream of water until the surface of the metal is +visible between the dots, the last traces of the soluble gelatine +being removed with warm water. After drying, the plate is evenly +heated over a Bunsen burner until the dots of gelatine mixture turn +chocolate colour, when the plate is allowed to cool gradually. This +is known as burning in. The plate, if necessary, is now touched up and +the back, sides and margins varnished in order to protect them from +the acid: when the varnish is dry, the plate is etched in a weak +solution (about 2-1/2 per cent.) of nitric acid if the metal be zinc; +if the plate be copper, it is usually etched with a solution of iron +perchloride. + +On taking a proof, there is almost certain to be a lack of contrast, +the plate is then fine etched, by which means a considerable +improvement can be made; and, by covering certain parts with an +acid-resisting substance ("stopping out"), it is possible to fine etch +locally. + +Incidentally it may be mentioned that machine etching, by which a fine +spray of the etching fluid is distributed over the plate, has recently +come into vogue, for it is claimed that the results print better and +are in other ways an improvement upon the older method. + +The plate may now pass through the hands of an engraver, who removes +any blemishes, as far as is possible, improves the high lights, and so +on; in fact, a skilful engraver can improve the plate considerably. + +After the plate is trimmed, and the superfluous metal cut out by means +of a routing machine, it is firmly tacked to a wooden mount, usually +of oak, but sometimes of mahogany, especially if the plate is large. +In order to obtain the best results, the printing, in a typographical +machine, should be done on highly calendered paper--so-called "art" +paper; in fact, this is absolutely essential if a fine screen has been +used; it is only the blocks made with the coarser screens that will +give fair prints on ordinary paper. For this reason reproductions made +by the half-tone process are very generally treated as plates unless +the glazed paper is used throughout the book. The process is used +principally for the reproduction of photographs, and for pencil or +wash drawings. + +With regard to photographs, it has already been mentioned that authors +should send the negative or two or three prints differently toned, +in order that the operator can choose the one most likely to give the +best result. + +It is sometimes difficult in a photograph of a landscape to obtain +a negative in which the particular feature it is desired to +represent--_e.g._, in photographs of vegetation--stands out with the +requisite contrast. This is due to the position of the sun at the +time of exposure, or to the use of ordinary plates. The remedy for the +first is to take the photograph when the proper light obtains; with +regard to the second, the use of colour correct plates, together with +a colour screen in front of the lens, will obviate the defect. Since +for scientific purposes the correct interpretation of the various +tones of the vegetation, for example, may not be essential, variously +coloured screens may be used in order to emphasise a particular +feature. For instance, it will be noticed how well the bushes in Plate +7 stand out. This effect was obtained by the use of a panchromatic +plate in conjunction with a red colour screen. + +[Illustration: PLATE 7.--Half Tone reproduction of a photograph taken +by Dr. Mees through a red screen.] + +With regard to drawings in wash, charcoal or pencil, in which +there are half-tones; these are better drawn on an enlarged scale, +especially if the author is not a skilled draughtsman, for improper +gradations in shading and other imperfections will not appear so +noticeable in the reduced reproduction. Originals should all be +made in one colour; in the case of wash drawings, diluted Indian ink +(really Chinese ink) will give excellent results. + +In making pencil drawings, a fairly stout hand-made paper with not too +much grain should be used. If the drawing is to be of some size, the +paper may be damped and pasted by its edges on to the drawing board, +it will then be stretched quite flat and will not cockle when dry. + +The outline of the object may first be sketched in lightly with a +soft pencil and then the shading may be proceeded with. To do this, +broad-pointed soft pencils, 2 B, 3 B, or 4 B, should be used, and it +is better generally to work from the high lights to the shadows. To +avoid rubbing finished parts, the work should proceed from the top of +the board downwards, especially in the case of large drawings. + +In order to obtain a nice gradation and a more smooth appearance--more +especially when a very coarse paper has been used--the work may be +gone over with paper stumps of appropriate size and softness, and, of +course, India rubber may be employed where it is desired to reduce the +density of the shading. + +When finished, the edges of the various parts may appear woolly owing +to the rubbing of the lead; this may be cured by cleaning up the edges +with a trimmed piece of India rubber, but in so doing there is always +a risk of rubbing out part of the shading, especially if the outline +be at all intricate. If preferred, all the shaded parts may be fixed +by painting them over with a suitable solution, gelatine for instance, +paying particular attention in following the correct outline. When +dry, the application of soft india-rubber will soon clean up the +blurred edges. + +If charcoal be used the same procedure may be followed. Charcoal and +pencil drawings should be fixed, in order to prevent rubbing, before +sending to the block makers. A suitable fixative may be purchased or +one may be made by dissolving white resin in alcohol and applying it +to the paper by means of a scent spray or an atomizer. A very good +fixative may be made by dissolving a little gelatine in hot water and +applying it whilst hot by means of a broad, flat camel hair brush, +or ordinary milk may be used in a similar way. After the fixative has +been put on, the drawing should be pinned up by one corner--unless, +of course, it was pinned up before the fixative was employed, which is +the best way when the fixative is an alcoholic solution--and allowed +to dry; it may then be placed under pressure in order to flatten it, +for fixed drawings generally shew a tendency to curl, especially when +the preparation used for fixing has only been applied to one surface +of the paper. + + +In making drawings for reproduction by means of the half-tone process, +there are a few general points to which attention should be paid. + +It should be remembered that there is not infrequently a tendency +towards flatness in the reproduction; it is therefore important that +the originals should be "plucky," and, on the whole, it is better to +exaggerate with regard to high light and shade, especially if there is +much modelling or perspective. + +Finally, with regard to lighting, it is better for the majority in +drawing their objects--solid objects in relief are referred to--to +use a more or less lateral illumination and to represent only the +high lights, shades and shadows referable to this main direction of +illumination. A high relief will thus be obtained, and the effect +will prove more satisfactory than if minor sources of illumination +are unsuccessfully dealt with. This is especially important in drawing +complicated structures such as models of vascular tissues, embryos, +etc. + +In cases where many such figures are to occur on one page, it is +highly desirable that the lighting of each should be from the same +direction. + +The use of the half-tone block is now almost universal, so that it is +hardly necessary to mention examples, more especially as they are hard +to judge without seeing the original picture. Those in the present +book are all of a high quality. Excellent examples will also be found +in Tansley's _Types of British Vegetation_ (Cambridge, 1911) and in +the _Journal of the Royal Horticultural Society_. + + +Proofs should be carefully compared with the originals, particular +attention being paid to the rendering of the tones; as already +remarked, fine etching will clear up a block and will often prove a +remedy to flatness. + +An author will naturally consider whether a photograph is to be +reproduced by means of photogravure, collotype or half-tone. It is +impossible to lay down any laws on the subject, but the following +points should be considered. + +If it is essential to have the reproduction in the text, a half-tone +block must be used; it must, however, be remembered that the paper +used for the letterpress may be very unsuited for the printing of +half-tones. On the other hand, if it be immaterial where the picture +is placed, then the relative merits of photogravure, collotype and +kindred processes and half-tone must be weighed. + +Provided that expense need not be considered, photogravure will, in +the majority of cases, give the best results; on the other hand, if +this process is too costly, then the choice lies between collotype +and half-tone. The latter method will often give a result with more +contrast as compared with collotype, whilst collotype will give a +truer interpretation of the tones. + +As has already been remarked, the best results with half-tone blocks +only are to be obtained by the employment of a paper which +seemingly has no lasting qualities; it therefore follows that if +the reproduction forms an important record, the use of collotype is +indicated, since many varieties of good paper are available. As a +general rule photo-micrographs are best reproduced by collotype. + +In order that the respective qualities of these three +processes--photogravure, collotype and half-tone--may be compared, +Plates 8, 9, and 10 have been made from the same photograph, a view +taken by Dr. F. F. Blackman of the Bouche d'Erquy, a salt marsh in +Brittany, which was selected chiefly on account of the large number of +tones it contains. + +[Illustration: PLATE 8. Photogravure] + +[Illustration: PLATE 9. Collotype] + +[Illustration: PLATE 10. Half Tone] + +These three plates are not entirely comparable, since the heavy +shadows in the right hand bottom portion of the photogravure have been +touched up by the engraver. This was not intended by the author, but +the plate was retained as it shews that directions regarding this +point should not be omitted when sending the drawing or photograph to +be reproduced. It also indicates that for critical work, when an exact +a facsimile as possible is required, collotype should be used, for the +plate cannot be touched up. + +With regard to the reproduction of drawings shaded by means of wash +or pencil, the same remarks apply, with the addition that if it be +possible to express what is desired by other means, suitable for +reproduction by line block, these latter should be employed. To +illustrate this point, Figures 5, 6, and Plate 11 have been inserted; +all illustrate the vascular skeleton of a fern (_Marattia fraxinea_), +the first one is in outline and the second is shaded by lines of +varying thickness; both of these are reproduced by means of the +line block, whilst the third is a reproduction by half-tone of a +pencil-shaded drawing. In order to obtain a fair comparison, the +half-tone is reproduced as a plate, owing to the fact that it would +not print satisfactorily on the paper used for the letterpress. + +[Illustration: Fig. 5] + +[Illustration: Fig. 6] + +[Illustration: PLATE 11] + + +THE HALF-TONE THREE COLOUR PROCESS.--This process is much used for +colour reproductions of various subjects; and, in view of the fact +that the best results can only be obtained by the best photography, +the object should, if possible, be sent to specialists for +reproduction. In many cases, however, this is impossible, _e.g._, +landscapes and animal and plant portraits amidst their natural +surroundings, so that the scientist, if unable to make a water colour +drawing, which will give by far the best result, must make his own +negatives. + +The first thing to do is to purchase a set of colour-filters, adapted +to the colour-correct plates to be used, from firms who specialize in +these matters, Messrs. Paget or Messrs. Wratten for instance, and +from them the inexperienced should obtain full information regarding +exposure, etc., for it is essential that the exposure of the negatives +should be correlated in order that all may have the same tone-value. + +The colour-screens, blue, green and orange, are made by dyeing +gelatine with suitable stains; the films are stuck on to perfectly +plane glass and are mounted in frames. In practice these screens are +usually placed behind the lens, in which case a special camera is +necessary, or they may be adapted to fit on to the front of the lens. +In either case the procedure is the same; three negatives are taken +one after the other through each colour filter, the exposure being +modified in order that the tones in each case may be of equal value. + +There are thus obtained three negatives which, of course, yield +positives which look very different one from the other. These prints +may be sent to the block makers, but it is better, on the whole, to +send the negatives with clear indications as to the colour of each. + +From each negative there is made by contact a transparency, and from +these positives there are prepared a set of half-tone negatives from +which are made the half-tone blocks. + +The reproductions are made by superposed printing of the three blocks, +yellow being printed first, then red, and finally blue (Plate 12). + +[Illustration: PLATE 12.--Three Colour Half Tone.] + +As indicated above, it is hardly worth while to make negatives for +this process unless the operator is a really skilful or at least an +efficient photographer, and even then the final product may prove +unsatisfactory. + +Better results are generally to be obtained by sending to the block +maker a Lumiere colour photograph with full instructions regarding any +corrections in the colours which may be necessary. + +Examples:-- + +Bateson: _Mendel's Principles of Heredity_, Cambridge, 1909. Church: +_Types of Floral Mechanism_, Oxford, 1908. Seward: _Darwin and Modern +Science_, Cambridge, 1909. + +PHOTO-MECHANICAL LINE BLOCKS.--The photo-mechanical line block, +commonly known as a zinco, is in a sense the lineal descendant of +the wood block. As a means of reproduction the possibilities of line +blocks are very great, for not only is it possible to reproduce by +their means all kinds of line drawings, but also drawings in charcoal +and crayon, provided they be suitably executed on a proper grained +surface. In fact, an artist or draughtsman who has a thorough +knowledge of the process and its capabilities can obtain extraordinary +results. The process has the further advantage of being both quick +and inexpensive, a few hours only being required to make the finished +product. + +Their mode of manufacture is the same in principle as for half-tone +blocks; in the case of the latter, the method known as the enamel +process was described; in the present instance a different procedure +may be dealt with. + +A photograph of the drawing is taken on a negative, the wet collodion +process being generally followed, although dry process plates may be +used. + +A highly polished zinc plate is sensitised with bichromate of potash +and gelatine, or by other means, and, when dry, is exposed under the +negative. + +The exposed metal plate is then taken into the dark room and evenly, +but thinly, coated with etching ink. When the ink is dry, the plate is +developed in water; the unexposed gelatine, and with it, the ink, will +come away, its removal being helped by the judicious application of a +dabber of wet cotton wool. + +The plate may next be "rolled over" with an ink which will more +stoutly resist the action of the acid than that used in the first +inking, but prior to this it is usual to soak the plate in a mixture +of gallic acid, phosphoric acid and gum. This second rolling up must +be carried out as if the plate were for lithographic reproduction; +and, when dry, powdered resin may be applied, in order to make a +better acid-resist, as in the preparation of a lithographic stone. + +The plate is now etched slightly in a weak solution of nitric acid; it +is then rinsed, dabbed dry and placed upon a hot plate until the resin +has stuck well to the ink. When cool, the margins, sides and back are +protected from the action of the acid by means of a varnish and the +plate is given its first real etch, which is a very slight one. After +rinsing and drying, the plate is again heated until the ink and resin +have melted and flowed down the exposed sides of the ridges of metal +produced in the first etching. This application of ink and resin must +be repeated in order that the exposed sides of the ridges may be well +covered with the acid-resist and so will not be undercut. The plate +is then given its second etch, and this is done with a stronger acid, +after which the sides of the lines are again protected with resinous +material in the same way as before. The third etch follows, after +which the metal is thoroughly cleansed from all the ink, etc. + +In order to smooth the shoulders of the lines, the plate is given a +finishing etch: the cleaned plate is warmed and rolled up with hard +etching ink; the metal is then heated until the ink becomes glazed, +and, when cool, is placed in the acid bath for the requisite amount +of time. If necessary the plate, after cleaning, is touched up with a +graver, and the superfluous metal is cut away. Finally it is mounted +on a block of wood, and after the corners and sides have been trimmed +square, the block is ready for the press. + +To illustrate the enormous improvement which may result from the block +passing through the hands of a skilful engraver, two line blocks of a +wood engraving by Riocreux (see p. 36) have been prepared. Fig. 7 is +the impression given by the block as ordinarily turned out, whilst +Fig. 8 is a precisely similar block which has been worked up by an +engraver. + +[Illustration: Fig. 7] + +[Illustration: Fig. 8] + +There are several other methods of making the blocks, but the +principles are the same as in the foregoing process. + +In examining the proofs it must be remembered that deletions are not +the only alterations that can be made in the finished block; not only +can lines be cut away, or their character altered by removing part +of the metal from them, but additions can be made in reason. For +instance, lines can be added across open spaces, and if part of the +printing surface has been accidentally removed in cutting away the +superfluous metal, the damage can be made good by building up with +solder and working on this with the graver. If, however, the additions +required are at all extensive or complicated, it is better to have a +new block made. + +Inasmuch as scientific illustrations are to describe and explain +definite facts, the drawings must needs be materialistic rather than +suggestive; in other words, a more or less conventional system must be +employed. + +In making their drawings for reproduction by line blocks, authors have +at their disposal the black line, the white line, the black space, +the white space, the black dot and the white dot, all of which may be +combined in various ways. No tones, other than black and white, are +available; if it be desired to represent half-tones, they must be +rendered by the above-mentioned means. + +In the majority of cases the originals should be made with black ink +on white Bristol board or smooth white paper; ordinary lead pencil +drawings on smooth paper are useless, and lead pencil, black crayon +or charcoal in combination with grained paper or board should not +be employed unless the draughtsman has the requisite skill and knows +exactly the limitations of the line block. For all ordinary folk black +ink and Bristol board cannot be improved upon. + +The drawing may be made first with a soft lead pencil, using the +camera lucida or other optical aids to correct delineation. The pencil +lines are then gone over with ink; for this purpose a good black +ink is necessary. Wolff's Indian ink, Higgins' waterproof ink and +Steuber's waterproof drawing ink are highly satisfactory, and +there are many others. With regard to pens, a suitable implement is +all-important; Gillott's lithographic pens and Brandauer's No. 515 are +recommended. For straight lines of an even thickness a ruling pen is +very useful, and these may be obtained fitted with an adjustment which +enables the worker to rule a line of a definite thickness, _e.g._, .5 +mm. and so on. + +All drawings should be made larger than it is intended the +reproduction to be, for slight inaccuracies, ragged lines, and other +blemishes will thus appear less obvious. This drawing on a large scale +is often a stumbling block, because the work appears too open and the +draughtsman is tempted to put in too much; this must be avoided, else +the crowded lines may join together in the reduced reproduction. Also +it must be remembered not to draw too finely, else the work in parts +may disappear entirely in the reproduction. In drawing on an enlarged +scale a certain amount of exaggeration may be employed, in order that +when reduced the drawing may not be quite spiritless. + +When representing a solid object, such as a plant or an animal, to +shew the external morphology, it is to be borne in mind that form +is the main thing to represent, and this can be expressed by outline +drawing alone. In fact, more or less primitive methods must be +employed, and better models cannot be followed than the best wood +cuts. + +[Illustration: Fig. 9. The Lesser Celandine (_Ranunculus Ficaria_). By +R. G. Hatton. (From Hatton's _Craftsman's Handbook_).] + +[Illustration: Fig. 10. The Lesser Celandine. After Fuchs. (From +Hatton's _Craftsman's Handbook_.)] + +An examination of figures 10 and 12 will shew that Fuchs[A] attained +his object by simple outline drawings; he never employed local colour, +and shading he used very sparsely indeed, and then only to give +expression to the form of some thick part. Fuchs's celandine (Fig. 10) +should be compared with the drawing of the same plant (Fig. 9) by R. +G. Hatton. + + [Footnote A: The methods followed by the illustrators of + the Herbals may be conveniently studied in Hatton's "The + Craftsman's Plant Book," London, 1909, and Arber's "Herbals," + Cambridge, 1912.] + +[Illustration: Fig. 11. The Apple (_Pyrus Malus_). After Matthiolus. +(From Hatton's _Craftsman's Handbook_).] + +The methods of Matthiolus (Figs. 11 and 13) were somewhat more +advanced, for he used shading not only to express form but also to +give a certain amount of relief. It will be noticed that he shaded by +lines which followed the moulding of the parts. + +The work of Riocreux (Fig. 8) should also be studied; it will be +observed that he managed to get a very high relief in his drawings by +the simple means of straight or curved lines, according to the shape +of the part, of varying thicknesses. + +[Illustration: Fig. 12. Charlock (_Brassica Sinapis_). After Fuchs. +(From Hatton's _Craftsman's Handbook_)] + +There is no necessity for keeping all the lines of even thickness. +For instance, provided the character of the form is not altered, the +outline on the shaded side may be made thicker than on the illuminated +side; also distance can be indicated by the use of thinner lines, for +these, although really black, will give the impression of greyness. +Then again, a line may be drawn with local increases and decreases in +thickness, as in ordinary writing, and such lines drawn by a skilled +hand can be made to express a marvellous amount of modelling. + +[Illustration: Fig. 13. Sea Lavender (_Statice Limonium_). After +Matthiolus. + +(From Hatton's _Craftsman's Handbook_.)] + +The draughtsman, however, is not restricted to lines; any marks which +can be made with a pen and black ink may be employed, provided they be +sufficiently firm and large. + +The accompanying figure (14) which is a reduction of an illustration +in Church's _Floral Mechanisms_, illustrates the use of lines of +varying lengths for shading. + +[Illustration: Fig. 14. _Viola odorata_: Floral morphology. A +reduction of a figure in Church's _Floral Mechanisms_.] + +In shading, the effect of shadow may be obtained by increasing +the thickness of the lines, but they must not be drawn too closely +together; on the other hand, the lighter parts can be represented by +thinner lines placed further and further apart, and the lightest parts +by the white of the paper. Cross hatching may also be employed (see +Fig. 15), but the crossed lines must not be too close together, for +otherwise they will tend to thicken in the making of the block and so +will print too black. + +[Illustration: Fig. 15. A Seedling of _Abronia villosa_.] + +For very delicate shading and tinting, stipple may be employed, +but the dots must be quite definite, sufficiently large to stand +reduction, and not too close together (Figs. 18, 28c, and 32). A +particularly good example of this method will be found in Butler's +paper on _Allomyces_ in the Annals of Botany, 1911, vol. 25. Dots have +also been employed in Fig. 28c (p. 69). + +With regard to local colour; this may be indicated by shading, by a +white space, or by a black space. + +Hitherto, drawing with black ink on white paper alone has been +considered, but the reverse is equally available; much can be +expressed by drawing with white ink on black paper. + +Drawing in white upon a black ground is not frequently attempted, but +an excellent example by Miss Janet Robertson is shewn in figure 16, +which is well worthy of study, since it illustrates to a nicety some +of the means at the disposal of the draughtsman for line blocks. The +black surface is best obtained by the use of a waterproof Indian ink +applied with a brush to a white surface, the drawing being made with a +dense white ink, using a pen or a brush. The white ink may be made by +diluting any good opaque white water-colour paint, or process white +may be used. The composition of this should be zinc oxide or baryta, +for these do not darken with age; the author once used for this +purpose a white pigment which proved excellent at the time; the +drawings, however, subsequently turned dark brown owing to the fact +that the basis of the paint was apparently a compound of silver. + +[Illustration: Fig. 16. _Neuropteris Heterophylla_. + +A line reproduction of a drawing by Miss Janet Robertson.] + +The top part of the drawing (Fig. 16), shewing the general morphology +of the plant, was drawn with a brush charged with white ink upon a +black ground. In the simplest possible way relief has been obtained by +representing the leaflets of the nearer fronds by white spaces, whilst +those further away are represented by white outlines. An enlargement +of a frond is shewn on the lower part of the picture, and here the +parts are represented in black on a white ground. The leaflets are in +black outline and the fruits are made to stand out, as in the upper +part, by the use of local colour--in this instance black--their shape +being indicated by the curve of the higher lights. In brief, a very +effective drawing has been made by the simplest use of the white line, +the white space, the black line and the black space. + +[Illustration: Fig. 17. _Fucus volubilis_, var. _Flexuosus_, a +seaweed. + +(From a drawing by Miss Baker.)] + +This may be compared with figure 17, which was drawn by Miss Baker; +the method pursued is entirely different to the last, it being a pure +pen and ink drawing on white paper. No local colour has been employed, +and the modelling has been expressed by the lines used for shading +which have been made by short strokes with a fine pen. The result +is suggestive of an engraving but this was not intentional; under no +circumstances should an attempt be made to imitate in a relief block +effects which can only be obtained by intaglio. + +From what has been said it is obvious that the photo-mechanical line +block can be used for the reproduction of all kinds of drawings in +pure black and white; to illustrate this figures 18-26 have been +inserted. + +[Illustration: Fig. 18. The Larkspur (_Delphinium ajacis_). By R. G. +Hatton. (Hatton, _Craftsman's Handbook_.)] + +[Illustration: Fig. 19. Hollyhock (_Althaea rosea_). By R. G. Hatton. +(Hatton, _Craftsman's Handbook_.)] + +[Illustration: Fig. 20. A Liverwort (_Lepidozia reptans_). (Evans, +_Annals of Botany_, 1912, vol. 26.)] + +[Illustration: Fig. 21. A Seedling of _Bruguiera gymnorhiza_, a +mangrove. Drawn by Mrs. F. E. Fritsch. (Tansley and Fritsch, _New +Phytologist_, 1905, vol. 4.)] + +[Illustration: Fig. 22 + +A diagrammatic sketch by Mrs. F. E. Fritsch of _Rhizophora conjugata_, +a mangrove. (Tansley and Fritsch, _New Phytologist_, 1905, vol. 4.)] + +[Illustration: Fig. 23 + +A shoot of _Acanthus ilicifolia_, a mangrove. Drawn by Mrs. F. E. +Fritsch. (Tansley and Fritsch, _New Phytologist_, 1905, vol. 4.)] + +[Illustration: Fig. 24 + +A longitudinal section of a fossil seed, _Conostoma oblongum_. Drawn +by Dr. E. J. Salisbury. (Oliver and Salisbury, _Annals of Botany_, +1911, vol. 25.)] + +[Illustration: Fig. 25 + +The Meadowsweet (_Spiraea ulmaria_), shewing four years' growth. +(Yapp, _Annals of Botany_, 1912, vol. 26.).] + +[Illustration: Fig. 26. The Chesil Bank. (Oliver, _New Phytologist_, +1912, vol. 11.)] + + +THE DRAWING OF MICROSCOPIC DETAILS. + +Questions relating to the drawing of microscope sections may now be +dealt with. Usually these are drawn in pencil and reproduced by means +of lithography; this is quite wrong, for in addition to its being an +unnecessary expense, it is also an inconvenience to a reader, since +the figures are necessarily divorced from the letterpress. There are +very few histological details which cannot be represented by line +blocks, and with a proper co-operation between the author, the +block maker, the printer and the publisher, even the delicacies of +karyokinesis could be reproduced in the text. + +For demonstration purposes, transverse sections of plant-structures +may first be taken. + +The walls of the various elements may be represented by lines of +more or less equal breadth, but in those cases where the walls are +particularly thick, _e.g._, the elements of the wood, the thickening +may be represented by an additional line. This is seen in Fig. 27, in +which it will be noticed that the middle lamellæ of the wood-elements +are represented by black lines. + +[Illustration: Fig. 27. + +(From Butler's paper on Gummosis of _Prunus_ and _Citrus_. _Annals of +Botany_, 1911, Vol. 25).] + +This is a particularly good drawing, but, unfortunately, it has been +over reduced. + +On the other hand, the various tissues may be represented by lines +of varying breadths, the thickest walled cells having the same double +contour as in the above, but with the addition of local colour in +the shape of diagonal shading. This is not uncommonly found in +papers dealing with the anatomy of plants by French authors; it is +illustrated in Figure 28 _a_. If preferred, such thick-walled elements +may be entirely represented by thick black lines as in Figure 28_b_, +and when such cells are relatively few in number, this method has much +to recommend it since a greater relief is obtained. + +[Illustration: Fig. 28 + +_a_ + +_b_ + +_c_ + +A transverse section to shew the vascular cylinder of the root of the +spinach, _c_ is somewhat older than _a_ and _b_.] + +Finally, an attempt may be made to draw in a more detailed fashion +as in Figure 28_c_. Here the thickness of the cells of the wood is +represented by broad black lines, the middle lamellæ being left white. +The lines marking the boundaries of the other cells vary slightly in +thickness, but this is to a great extent masked by the representation +of the cell contents, which consist entirely of dots in the case of +the protoplasm, whilst the nuclei are represented by dark ovals--black +relieved with small white areas. By varying the size of the dots and +their distance apart, varying densities can be indicated. + +It has been mentioned above that it is possible to reproduce fine +detail by means of the line block; this is illustrated in Figs. 29 and +30. + +[Illustration: Fig. 29] + +Fig. 29, which illustrates a stage in the division of a nucleus, +was drawn with black crayon on a rough-grained piece of Whatman's +water-colour paper. The cytologist will, doubtless, criticize its +coarseness, but it may be mentioned that the roughest paper at hand +was designedly employed in order to illustrate the point raised. That +a finer grained paper will give more delicate results is shewn by Fig. +30, which is a reproduction of a drawing, kindly lent by Dr. W. G. +Ridewood, made with ordinary lead pencil on grained Bristol board. Its +delicacy is obvious, and at first sight it could easily be mistaken +for a lithograph.[A] + + [Footnote A: Many similar examples will be found in Ridewood's + memoir _On the Cranial Osteology of the Clupeoid Fishes_, + Proc. Zoo. Soc., Lond., 1904, vol. 11, p. 448.] + +[Illustration: Fig. 30] + +A half-tone can be put on to a line block during its manufacture. All +that the draughtsman has to do, is to indicate by blue pencil lines +those parts on which he requires the dots, which give the half-tone, +to be placed, and to select the pattern of the stipple he desires to +be used. The result may appear somewhat mechanical since the dots +are regularly arranged, but a drawing sometimes may be considerably +improved by this means if used with judgment. It is frequently +employed in representing drapery, and many examples may be found on +those pages of newspapers devoted to ladies' dress (Fig. 31; see also +Fig. 32). + +[Illustration: Fig. 31. After a water-colour design by Miss Winifred +Pearse.] + +THE DRAWING OF DIAGRAMS AND APPARATUS. Much valuable information may +be conveyed by diagrams; in fact, these could be used more freely than +they are. + +[Illustration: Fig. 32] + +The principles to be borne in mind are the same as for other ink +drawings. They should always be drawn upon an enlarged scale, and with +as little detail as possible, which generally should be indicated +in the most conventional ways--dots, black spaces, lines, and so on +(Figures 33 and 34). The main thing to be aimed at is clearness, so +that it is often necessary to sacrifice true relative proportions in +order to gain this end (Fig. 34). + +[Illustration: Fig. 33. A diagram by Mr. E. Lee. (_Annals of Botany_, +1911, vol. 25.)] + +[Illustration: Fig. 34 + +A Diagram from the _Annals of Botany_, 1912, Vol. 26.] + +In certain cases it is possible to combine detail and diagram in one +drawing; this is shewn in Fig. 32, taken from Dr. Ridewood's admirably +illustrated memoir on the _Gills of Lamellibranchiata_ (Transactions +of the Royal Society of London, B. vol. 195, 1903). The shading +employed was either done by the draughtsman (at _ch_ and in the cells +with irregularly arranged dots), or else was put on the block during +its manufacture (_af_). If a lens be used, the difference will at once +be obvious. + +The finished drawing should be bold and neat, and all lettering should +be very clear. If several figures are included in one diagram they may +be separated one from the other by ruled lines, and in no case should +one tier of figures--taking the frames as the boundaries--unevenly +overlap another tier, otherwise the diagram, to use an expressive +phrase, will look "like a pig with one ear." + +Under the heading of diagrams must be included the representation of +apparatus. There are two ways of drawing apparatus; the objects may +be drawn as a study in still life, as, for example, in many of the +figures illustrating Deschanel's _Natural Philosophy_ (London, 1890) +or they may be represented in a purely conventional fashion. The +latter is the better way, and it is preferable to draw for the most +part in section in order that all connections, inlets, outlets, etc., +may be clearly shewn. + +A study of a good example is infinitely better than a written +description, wherefore Figure 35 has been inserted. + +[Illustration: Fig. 35] + +It will be observed that all glass vessels and tubing are represented +in section, and in the thermometers, the fine capillary bores are +represented by a single line in each case; corks by diagonal shading; +wood by lines in imitation of its grain; metal parts by vertical +shading or dead black; more or less still liquids by a series of lines +broken below and continuous at the surface, and gradually becoming +closer and closer together towards the surface. Mercury, on the other +hand, may be indicated by dead black relieved by a few white lines to +represent its reflecting surface, also its free surface may be drawn +convex. Finally thumb screws may be shewn by a combination of black +areas and vertical shading. + +These conventionalities need not all be followed; for instance, rubber +connexions may be indicated by broad black lines and wood by diagonal +shading. + +The drawing should be very bold and the different parts clearly and +freely indicated by writing or "printing." + + +THE DRAWING OF MAPS. In the drawing of maps for reproduction by the +line block process, if an existing map serves the purpose, a tracing +may be made in ink on translucent linen. If, on the other hand, the +author has to make his own map, the problem becomes more difficult. + +For the obtaining of the data for map making information must be +sought for elsewhere, since we are only concerned in the preparation +of the map for publication. And as regards this, but few general rules +can be laid down since the character of maps is so diverse. + +The amount of detail in the physical features represented depends to +a great extent upon the scale. Thus streams of a greater breadth than, +say, 10 feet, may in large scale maps be represented by double lines, +whilst no stream less than 2 feet in breadth will be shewn in low +scale maps. + +[Illustration: Fig. 36 + +_a_ Contoured. + +_b_ Spot-levels. + +_c_ Layered. + +These three figures illustrate in three different ways the varying +levels of a piece of ground surveyed by Prof. F. W. Oliver and Mr. A. +G. Tansley.] + + +The indication of hills is always a problem; the most satisfactory +way is by the drawing of contours (Figure 36_a_), and this whenever +possible should be followed, since it is scientifically the most +correct method, inasmuch as when properly drawn the form of the hill +is shewn exactly; further, contours obscure the detail to a much less +extent than does shading, and but little artistic talent is required +to draw them. If, however, contouring be impossible, the various +heights above the datum may be shewn by spot levels (Figure 36_b_) +or the relative levels may be shewn by layers; that is to say, by a +system of shading each kind of which indicates a certain level. Thus +dots may be used for all parts not more than 100 feet above sea level, +vertical lines for regions between 100 and 200 feet, horizontal lines +for parts between 200 and 300 feet, and so on (Figure 36_c_). It is +obvious that this method cannot be pursued if vegetation also is to be +shewn. The last choice is to represent the hill by shading in much the +same way as many of us did when children; the method referred to was +known as "herring bones" or "hairy caterpillars." + +The sea or a broad expanse of water may be indicated by fine lines +which follow the coast-line and which may be placed at gradually +increasing distances apart. + +If geological strata are to be represented, the accepted symbols +should be used; if the map is intended to represent the distribution +of soils, convenient signs may be employed, _e.g._, large dots for +shingle or gravels, small dots for sand, black areas for clay, and +so on; finally, if the distribution of plants or of animals is to be +shewn, symbols again may be employed. These, however, must be +quite simple and as far as possible give an idea of the organism +represented. This, in the case of animals, may be a difficulty, but, +with regard to plants, simple signs are easily inserted which give a +very good idea of the plant it is intended to represent. Many of the +signs used by the Ordnance Survey are ready to hand, and these can +often be used to designate plant associations. + +The delimitation of areas should always be clearly shewn, and all +names should be very clearly "printed" indeed, and if they must be +placed on a dark portion of the map, they should have a good white +border around them. + +The north should always be indicated. This may be done by drawing in +its proper position a representation of a compass or merely an arrow +pointing to the north. Unless otherwise stated, the arrow is assumed +to point to the magnetic north, and if no north be actually shewn it +is taken for granted by an intelligent reader that one of the vertical +sides is a true north and south line, with the north at the top. +Finally, under no circumstances should a scale be omitted--it is the +first thing a reader should look for. + +For a map to look well two things are all-important, neatness and +clearness; both of these may nearly always be secured by drawing on +a large scale, bearing in mind what has been said about crowding +the detail, etc., and carefully considering how much reduction the +original can stand. This last point is of vital importance, for an +over-reduced map is an abomination; we have seen really good maps +absolutely ruined by this stupid error. + +The inexperienced author should study the methods pursued by Prof. +Yapp in Figure 37. For comparison, the simpler way adopted by Mr. +Wilson may be studied (_Annals of Botany_, 1911, Vol. 25). + +[Illustration: Figure 37. A Map of the Fenland by Prof. Yapp. (_New +Phytologist_, 1908, Vol. 7)] + + +GRAPHS OR CURVES. Simple though it be, the plotting of a curve for +reproduction requires thought and care. In the first instance, the +curve is drawn on squared paper, and the question naturally arises--To +what extent are the squares to be represented? If it be desired to +reproduce all the lines, say the paper is ruled in millimetres, a +half-tone may be employed, or all these lines can be ruled over in +black ink where the reproduction by line block is possible. It is, +however, seldom necessary to represent all the smallest squares; it +will generally be found that the centimetre squares are sufficient. If +the original be plotted on paper which is ruled in pale blue, it can +be reproduced by line block without re-drawing, since the blue will +photograph as white with the plates commonly used; all the essential +lines and curves must, of course, be in black. If, however, the +rulings of the squared paper are in red, yellow, or dark blue, a +tracing must be made. The horizontal and vertical sides should be +ruled with a broad black line, but the internal intersecting lines +should be much thinner. The actual curve may be in a continuous line +if one only be shewn on the graph; if more are drawn, then each must +be different, the obvious variations being the thick continuous line +---- the thin continuous line ----, dashes either thick or thin +---- ---- ----, dots . . . . . , and finally combinations of dots and +dashes ---- . ---- . ---- . + +Owing to the difficulty which some experience in drawing freehand a +continuous line, the plot should be made twice the linear size of the +intended reproduction. A good rule to follow in drawing lines is to +keep the eye fixed on the point where the line is to end, the hand +will then guide the pen in the right path, especially after a little +practice. In many cases the ruler may be used, not only for straight +but also for curved lines, for good curve rules may be purchased. + +In order that the figure may look neat, the lines should be of an +even thickness throughout their length; this is easily accomplished by +means of a ruling pen. + + +It has been stated above that Bristol board is the best material to +use for the making of drawings for line blocks; other materials may, +however, be employed, although they are not so nice to work upon. + +For instance, it may be necessary to reproduce a map; this, as has +already been mentioned, may be conveniently done by pinning over the +map a sheet of pale blue tracing linen, and tracing the map on this +with Indian ink. The fact that the linen is blue does not matter, for +it will photograph as if it were white. + +Then again, many subjects may be of so complicated a nature as to be +beyond the skill of the author to draw. In such a case a good plan +is to take a photograph of the object and make a positive on smooth +bromide paper, which need only be developed sufficiently far to give a +print which just shows the features. The print, when dry, can then be +worked on with fixed Indian ink. The finished drawing, when quite dry, +may be immersed in any solution which will dissolve out the silver; a +solution of iodine in potassium iodide answers sufficiently well. The +print will turn very dark, but it must be allowed to remain in the +bath until all the silver has dissolved; it is then removed, rinsed +under the tap and placed in an ordinary fixing bath of hyposulphite +of soda. All the colouration will be quickly removed so that the ink +drawing will stand out well against the white paper. All that it now +requires is a thorough washing in water; when dry it may be touched up +and then placed under pressure in order to make it quite flat.[A] + + [Footnote A: The chief disadvantage of iodine solution is its + slowness of action; the following methods are much quicker. + (_a_) To a solution of 4 oz. of hyposulphite of soda in + one pint of water, add a 10 per cent. aqueous solution of + potassium ferricyanide until the mixture is lemon coloured. + When the silver image has quite disappeared, wash the print + thoroughly in water. Since the mixture does not keep, the + ferricyanide solution should be added to the hyposulphite + solution immediately before use. + + (_b_) Mix 125 ccs. of a 10 per cent. alcoholic solution of + iodine with 21 ccs. of a 10 per cent. aqueous solution of + potassium cyanide, add to the mixture 1 litre of water. + When the image has disappeared, which will be in less than a + minute, wash for five minutes in water and dry.] + +This method of drawing over photographic prints will often save +a considerable amount of time. For instance, it may be desired +to reproduce a consecutive series of drawings to illustrate the +microscopic structure of the subject. The ordinary way of doing this +is to make camera lucida drawings of the sections, which is a lengthy +and tiresome process; a photograph of each section will take much less +time and will give quite as good results. + +Before sending any line drawings to press they should be carefully +examined; pencil marks may be rubbed out, lines touched up, +unnecessary lines removed by painting them out with white or black ink +according to the background, and, finally, a frame ruled around, if +necessary. + +The amount of reduction, which should be marked clearly on the margin, +requires very careful consideration since under reduction may cause +the reproduction to appear too coarse whilst over-reduction may result +in the loss of the finer detail and the drawing may, moreover, appear +spiritless. + +It must also be remembered that a reduction of, say, 1/2 linear means +that the reproduction will be a quarter the area of the original. + +The best way to indicate the reduction required is to draw a vertical +or horizontal line, parallel to a side or the base of the picture, +of the exact length; or, the line may be roughly drawn and its length +indicated by figures thus ------------2-1/2"--------- . + + +The question arises as to when line drawings for reproduction by the +zinc block should be employed. + +The answer is, Whenever possible. + +The advantages to a reader of having the illustrations in the text +has already been commented upon. It is about the only method commonly +employed in which practically everything depends on the draughtsman; +the author thus exercises the greatest control. Finally the fact that +it is very inexpensive will appeal to editors and publishers. + +As a matter of curiosity, the present writer picked out at random a +recent volume of a scientific journal to examine the illustrations; +although there were a number of text figures, an examination of the +plates--chiefly lithographs and collotypes--showed that there were a +large number of figures which ought to have been in the text. A more +detailed inspection of the plates was therefore made, with the result +that nearly 200 figures were found which with the minimum amount of +alteration--merely drawing in ink instead of pencil in the majority of +cases, and leaving out unnecessary shading in the others--could have +been reproduced by line blocks. If this had been done, a saving of +over 20 per cent. could have been effected on the plates. Some of this +would, of course, have been absorbed in the making of zincos, but +not much, since line blocks of excellent quality can be obtained for +2-1/2d. and 3d. per square inch. The above relates only to the most +obvious examples; the saving in plates would have been enormous if the +authors had drawn for the line process. + + +THE SWELLED GELATINE PROCESS. From the foregoing account of the +line-block it may, perhaps, be thought that a drawing shewing the +finest detail cannot be reproduced in the text by a relief block made +by photo-chemical means. This is not the case; the swelled gelatine +process is such that at its best the very finest work can be so +reproduced. The method is not extensively used, chiefly owing to the +remarkable amount of skill required to produce the best results and to +the facts that the blocks take longer to make and are more expensive +than the ordinary line block. This, however, should not militate +against its use, for the increased cost is but very little, and the +longer time in making, say two days, should not be of any consequence +in a monthly or quarterly periodical. The great point in its favour is +its great fidelity as compared with the ordinary photo-chemical relief +blocks: for instance, a close cross-hatching reproduced by a line +block will often come out as a series of white dots owing to the fact +that at the points of intersection the black lines tend to thicken; +hence, on printing, the white spaces, instead of being sharply cut and +diamond-shaped, are rounded. This will not occur in a good block made +by the swelled gelatine method. Further, the process does not restrict +the draughtsman to dead black ink; the drawings may be made in pencil, +crayon, or in ordinary writing ink: it is even claimed that wash +drawings and photographs can be reproduced satisfactorily by this +method. In the case of pencil drawings, the best results will be given +when the surface of the paper used by the draughtsman is slightly +rough; a pencil drawing on Bristol board, for example, will not be so +well reproduced as one on ordinary smooth drawing paper. In brief, the +process is as follows: a photographic negative of the drawing is made, +and under it is exposed a bichromate gelatine plate. This plate is +then developed in water. As already described, the gelatine will swell +up in proportion to the amount of light to which it was exposed. The +"positive" thus obtained will be in relief, the high lights being at a +higher level than the shadows. A wax mould of the gelatine positive +is then taken, covered with a thin layer of plumbago and electrically +covered with copper. The "casting" so obtained is built up with metal +and then mounted on wood in the same way as a zinco or a half-tone. +The capabilities of the process may be judged by a study of Fig. 38, +which is an extremely faithful reproduction of a lithograph, by S. +Prout, by the swelled gelatine process. + +[Illustration: Fig. 38. A Lithograph by S. Prout reproduced by the +swelled gelatine process.] + +[Illustration] + + + + +COST + + + + +RELATIVE COST OF BLOCKS AND PLATES + + +The question of cost is one of very great difficulty; in all +probability no two firms will agree in their quotations for different +kinds of work, and the reason for this lies in the large number of +factors involved, many of which are very difficult to compute exactly. +With respect to line engravings, etching, mezzotint, wood cuts and +wood engravings, it is impossible to give any idea of the cost. It +depends entirely on the complexity of the subject and the artist +employed. + +As regards lithographic processes for reproduction in one colour the +cost varies with the nature of the work. If an artist be commissioned +to make an autolithograph, the fee would be agreed upon beforehand. +Photolithography and collotype, on the other hand, are processes +which do not require the hand of an artist, and these methods of +reproduction are relatively inexpensive. The price quoted by the +lithographer or collotyper is for printing so many copies, hence the +relative cost per copy depends upon the run and on the quality of +the paper used. Lithography is cheaper than collotype; but if several +illustrations are sent at the same time to be reproduced by collotype, +the cost for each would be less than if sent separately. + +In chromolithography a separate stone is necessary for each colour, +hence the cost depends upon the number of stones used, and as several +may be necessary to obtain a first-rate reproduction, it is obvious +that the process may prove very expensive. + +Turning to photomechanical processes, the prices vary according to the +grade of work required--the best possible, good, and, lastly, cheap +work. By best possible is meant the best that can be made under +existing conditions, the price being immaterial; in good work the cost +will be a limiting but not a preponderating factor, hence the work +will be open to criticism; finally, in cheap work, the price is all +important, so that the result is a block or a plate which will print +well but which must not be criticized as regards its being a faithful +reproduction of the original. + +It is obvious that in the last two cases the quality of the work will +depend upon the agreed price, whilst in the first case the cost will +depend on the amount of time and skill required. + +It is obvious, therefore, that a comparison of cost cannot be made +between these grades; it is, however, possible to draw up a scale of +relative cost of the processes under consideration for work of the +same grade. In the table given below, A represents the best possible +work, B indicates good work, and C stands for cheap work. Since the +line block is the least expensive it is taken as the unit of price; +that is to say, if a line block costs 3d. per square inch the cost of +half tone, three colour half tone and photogravure would be 7-1/4d., +3s., and 1s. 2-1/2d. respectively. + + A B C + Line 1 1 1 + Half tone and swelled gelatine 2-1/2 2-1/4 2 + Half tone three colour (three plates + required) 9 12 10-1/2 + Photogravure 4-1/2 4-3/4 5 + +It must not be thought that if the area of a block is 3 square inches, +the cost will, therefore, be 9d. There is, for obvious reasons, a +minimum size at which the block or plate is charged although it may be +smaller. These minima vary; in general terms they may be taken as 12 +inches for line, half tone and swelled gelatine blocks, and 20 +inches for half tone three colour blocks and photogravure plates. The +measurements are the areas of the etched surface, the actual plate or +block may be larger, but for this margin no charge is made. + +With regard to cost of printing, nothing need be said about blocks +which are set up with the type, namely line, swelled gelatine and +coarse half tone blocks. The price of printing fine half tones and +three colour blocks depends upon the quality of the paper used and +the fineness of the work. Photogravure plates must be hand printed +(photogravure printing on rotary machines is not considered here), and +skill is required; for ordinary printing on good plate paper the +price would be 10s. to 12s. 6d. per hundred copies, whilst for India +printing the cost would be about 25s. for the same number. + + + + +LITERATURE + + + Barnes: _Illustrating Botanical Papers_, Botanical Gazette, + Vol. 43, 1907. + + Bock: _Zincography_, London, 1910. + + Cumming: _Handbook of Lithography_, London, 1904. + + Cundall: _A Brief History of Wood-Engraving from its + Invention_, London, 1895. + + Gamble: _Line Photo-engraving_, London, n.d. + + Hamerton: _Drawing and Engraving_, London, 1892. + _Etching and Etchers_, London, 1880. + _The Graphic Arts_, London, 1882. + + Pennell: _Lithography and Lithographers_, London. + + Richmond: _Grammar of Lithography_, London, 1909. + + Robertson: _The Art of Etching_, London, 1885. + + Verfasser: _The Half-tone Process_, London, n.d. + + Wilkinson: _Photo-mechanical Processes_, London, n.d. + + * * * * * + + + + +Transcriber's Note + +Some extraneous Headings on otherwise blank pages have been removed. + +Each Footnote has been indented and placed beneath the paragraph to +which it refers. + +The Plates, which were on un-numbered pages, and some of the Figures, +have been moved to (usually) below the paragraphs which first refer to +them. + +page 35: 'revelant' corrected to 'relevant' ... "See also the relevant +works cited under Literature" + +page 90: The Table of Costings does not appear to make sense, but has +been left as in the original. + +Hyphenation is not consistent in this book. + + + + + + + + + +End of the Project Gutenberg EBook of The Essentials of Illustration, by +T. G. 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