Raymer's Old Book Store 1330 First Are. SEATTLE, WASHINGTON J Digitized by the Internet Archive in 2014 https://archive.org/details/phototrichromatiOOzand PHOTO^ : : : TRICHROMATIC PRINTING : : Prisn^ahic Solai' Spechh-urr) A a B C E b F punda mental ■ pundament^ 1 fTundamentgi ■ 1 F^ed 1 Green 1 Violet A D H 5pec^rum of Sodium. (No) PrimaKy Red, GKeen and Violet overlapping , •forming Yellow, C^^an-Blue and Crimson. Whil"e in ce^^^e photo s:XLncbromatic lP>innting :::::: : : : : : 3n ^Cbeor^ ant> practice. By C. G. ZANDER. Published by Raithbyt Lawrence & Co*, Ld», Leicester* THIS SMALL VOLUME IS DEDICATED TO DAVID HARRIS, ESQ., F.R.S.E., F.S.S., OF EDINBURGH, AS A TOKEN OF SINCERE REGARD BY THE AUTHOR. PREFACE. Let there be Light." — Gen. i., 3. ^T^HIS hook makes no pretension to be a textbook on the optical ^ sciences of chromatics and spectroscopy . I merely inteiid giving the general reader , artists, and colour-printers in particular, a short outline in the plainest possible language of the causes of colour phenomena and the effects of pigmentary mixtures and combinations. Without at least some elementary knowledge of chromatics, the colour-printer, who attempts Photochromic Three- Colour work, will always grope in the dark, and can never hope to achieve great success. In fact, my experience is, that the lack of knowledge generally prevailing on the subject of chromatics, even amongst those who use colours in earning their daily bread, is unpardojiably great, and is one of the reasons ivhy trichromatic printing does not make the headiuay it deserves. As lue should not criticise without being able to supply a remedy, I thought it best to produce a small book lahich would serve printers and artists as a liandy guide taithout troubling them with scientific intricacies. For the benefit of those icdio, through the perusal of this booklet, may desire more knowledge, I append a list of books which may be studied ivitli profit. They luill supply proofs of the facts luhich in the compass of these few pages I have only been able to state without fully proving. One of tJie purposes of our existence — the acquisition of knoivledge — is mainly accomplisJied through the instrumentality of our eyes. It is therefore not surprising that the investigation of colour phenomena is one of the niost fascinating of studies, giving endless pleasure quite apart from tJie utility which it affords to those who use colours in their daily vocation. / hope that niy attempt to explain the laws of colour phenomena and their application to Three-Colour work, in plain homely language — intelligible to every artist or printer requiring to have at least an elementary knowledge of the principles of a process which is one of the most interesting achievements of modern science — will meet with a kindly reception, and that any imperfections caused by tlie attempt to condense a very wide and difficult subject will be pardoned. C. G. Z. London, April, 1896. BIBLIOGRAPHY. Abney, Captain . . "Colour Measurement and Mixture" (London, i8gi). Abney, Captain . . " Colour Vision " (London, 1895). Rood, 0. N "Modern Chromatics" (London, i8go). Bezold, W. von . . " Theory of Colour " (Boston, U.S.A., 1876). Chevreul . . . . "Colour" (London, 1887). Field, G "Chromatography" (London, 1885). Church "Colour" (London, 1891). NiEWENGLOWSKI, G. H. " Les Couleurs et la Photographic" (Paris, 1895). VoGEL, Dr. H. . . . "The Chemistry of Light" (London, 1892). LoMMEL, Dr. E. "The Nature of Light" (London, 1895), LocKYER, J. Norman . "The Spectroscope and its application." LocKYER, J. Norman . "Studies in Spectrum Analysis" (London, 1894). Proctor, R. A. . . "The Spectroscope and its work" (London, 1888). "The Chemistry of Photography" (London, 1891). Abney, Captain . . " Photography." THE BOOK AND ITS MESSAGE . SPEED little Book. In colour loving mind Of Caxton's son, now plant this germ of power. Black slaves too oft, like most of human kind. The world's more leaden hued than God designed. God was an Artist in Creation's hour ; What meaning else have blooms of tree or flower ? See Nature's lavish brush, her myriad glow, Free, without gold or price, where'er we go. Let Art of like beneficence now dream, Everywhere tint and colour, glint and gleam Speed little Book, and say to men, " Have done With faithless cold misgivings." Tell the one Who, loving beauty, fears that love to trust. That God must reign, and therefore Beauty must Read here of White, of purity the mark Read here of Black — on brightest hour comes dark White is no mere negation, no mere \ oid ; But blent of colours brilliant, unalloyed. What movements and what lustres are in this Sweet badge of purity — not cold I wis — Full sum ot hues ; warm energy of bliss. And Black is blent of brightness. Swift a spell E\ okes the beauties which within it dwell ; Primrose's yellow; rose leaf's red, and green Of meadow sward, all merging here their sheen. At magic touch, from Black they several fly Like hopes we lost awhile, which did not die. Speed Booklet ! Tell thy message. How the man Who could not charm with colours, henceforth can. This portion of its vast and fruitful fields Lithography to joint possession yields. Though rude his press, mayhap — if care be shown — Each printer yet may make this art his own. The colour feast he offers to the eyes Commends his artist mind and proves him wise. His work, exalted to a higher plane. Redounds to praise again, and yet again. To those who seek his skill he gives a choice At which they, too, not less than he, rejoice. For oft "effect, effect" alone is sought. Nor gold close reckoned if "effect" be wrought. Speed printer. Make avail of beauteous hues Which lend enchantment to the simplest views. Profit by these strange powers, undreamt before. Which proffer aid at every printer's door. Study this volume. Con its colour lore. F. COLEBROOK (Editor " Frinting Times and Lithographc! PART 1. Chromatics* Spectroscopy* The three fundamental Colour Sensations. Complementary Colours. The Young^HelmhoItz theory of Colour Vision. Colour Constants. PART I. /^^'^^^^^■i OLOUR has no material existence ; it is a sensation caused I ( by the excitation of the nerves of the retina of the \\^__^ the eyes. According to the Undulatory Theory of hght, the molecules of luminous bodies are supposed to be in a state of exceedingly rapid vibration and to communicate these vibrations to the ether, that highly rarefied substance, which is said not only to pervade all space, but also to surround the molecules of all matter. These vibrations or waves of the ether are exceedingly rapid and minute, the wave-length varying with different coloured lights. The length of the rays which excite the sensation of red, is about 3""9noo of inch, whilst the length of the rays which excite the sensation of violet is about yyJoo inch. Orange, yellow, green and blue are of intermediate lengths between the two. The velocity of light is 186,772 miles per second. To obtain an idea of the principle of the wave motion of light in the shape of a homely illustration, take a rope, perhaps ten feet long or longer, tie a number of knots in it and fasten one end to the knob of a door. Hold the other end in your hand and give it a rapid up and down motion. A wave-like motion will run from your hand along the rope to the door knob and the knots will move transversely to the direction of the vibration, but will practically maintain constant distances relative to one another, or to any fixed points such as your hand or the door knob. Another way of illustrating the wave-like motion of light is to fill a basin with water and strew it with a little sawdust. When the water and sawdust are perfectly still, drop a pebble or some other heavy body into the water. You will notice that concentric rings or waves spread or run from the place where you dropped the body in. This wave-like up and down motion of the water will be com- municated to the floating particles of sawdust, which here serve to mark the positions of the particles of water. These particles, when the agitation has passed, will have come to rest in precisely the same places where they were before. They will neither travel nearer the edge of the water nor nearer the place where the pebble was dropped in. The rapidly vibrating molecules of an incandescent body set up corresponding vibrations of the ether, and these wave-like move- ments spread in all directions, or as scientists call it, in concentric spheres. The particles of the ether move transversely to the path of the light as we have seen in the movements of the knots in the rope or the floating sawdust agitated by the water. If a ray of sunlight be permitted to pass through a small hole (or better, a narrow slit) in the shutter of a darkened room, and to pass through a prism — a triangular piece of glass — held in the beam, the ray of light will be spread out or dispersed, and on the opposite wall of the room a band of colours, as in the rainbow, will appear. These colours in their order are red, orange, yellow, green, blue, and violet, and they are called the colours of the spectrum. Sir Isaac Newton named the dark portion of the blue, where it merges into violet, " indigo," thus counting seven colours — the reason why we often hear or speak of " the seven colours of the rainbow." This experiment teaches us that white light is made up of many coloured rays, into which it can be disintegrated. Colour, therefore, may be taken to be a part of disintegrated white light. We shall see further on that coloured rays may be united again to form white light. FIG. I. — DISINTEGRATION OF WHITE LIGHT BY PRISM. 12 A darkened room and a slit in its shutter is a very cumbersome arrangement, and useless for the exact scientific analysis of light. For this purpose an optical instrument, called a spectroscope, has been devised. A large laboratory spectroscope usually consists of three movable tubes, arranged at angular distances of about 120° (or the third of a circle) from one another : in the centre of the circle is placed the prism. The collimating tube allows light to enter through a narrow adjustable slit and pass through a lens called the collimator, which causes the rays of light to fall parallel upon one or more prisms. These prisms bend or refract the light and break it up into its component parts or colours, which can be viewed through another tube, which is really nothing but a modified telescope. The best spectroscopes have yet a third tube, containing an engraved or a photographic scale, which can be seen through the observing telescope, simultaneously with the spectrum — a contrivance most helpful in spectrum analysis. Spectroscopes vary in their arrange- ments, but the principle upon which they are constructed is the same. A smaller and more convenient form of spectroscope is called a direct vision or pocket spectroscope, and contains slit, collimating lens, prisms and telescope all in one tube, which can be drawn out for focussing purposes. FIG. 2. J. browning's STUDENT'S SI ECTROSCOPE. 13 FIG. 3. — J. browning's pocket SPECTROSCOPE, If we view the spectrum of sunlight or the " solar spectrum," as it is called, we see a number of gaps or dark lines across the band of colours. These lines will always be found in the same position relative to the colours and alwa3's at the same relative distance from each other, and are, therefore, used as convenient landmarks. They were first described by the famous physicist, Dr. Wollaston, in t8o2. Fraunhofer minutely investigated and mapped them out in 1814, and they have ever since been called after him, Fraunhofer's lines. The principal lines are denoted by ten letters : — A, a, B, C, D, E, b, F, G, H. A and a are in the dark red end of the spectrum, B and C in the red, D in the orange-red, E and b close together in the green, F in the blue, G in the blue violet, and H at the violet end of the spectrum. Only the solar spectrum shows these Fraunhofer lines, which are due to the absorption of some wave lengths of light by gases in the sun's envelope. Electric, lime and gas-light, and all luminous solid and liquid bodies, give continuous bands of colours or spectra. Glowing vapours and gases do not show continuous spectra, but only bright lines on a dark background. These lines are different and charac- teristic for different substances, bemg always exactly the same for each chemical element. They have been carefully observed and mapped out, and form the basis of what is called " spectrum analysis." If light emitted by an incandescent body passes through a gas, a negative spectrum will result. The spectrum will then show dark lines in precisely the same places where the bright lines would appear on a dark ground, if that particular gas were itself in a state of incandescence. " The spectrum method of analysis is distinguished from ordinary chemical methods by its extreme delicacy. The three-millionth part of a milligramme of a salt of sodium, an imperceptible particle of dust to the naked eye, is yet capable of colouring the flame yellow and of giving the yellow line of sodium in the spectroscope. More than two-thirds of the surface of the earth are covered by sea, which contains sodium chloride or common salt. When waves are raised by the storm and their foaming summits are carried away, fine particles of salt are mingled with the air and carried far over the land ; common salt is consequently distributed through the whole atmosphere in the form of a fine dust. On account of this almost constant presence of sodium chloride, it is scarcely possible to obtain a flame which does not exhibit the yellow line of sodium. It is only necessary to strike a handkerchief upon the table, or to close a book sharply, to make the dust which escapes, colour the adjoining Bunsen's flame yellow, and to make the sodium line appear m the spectroscope." (Lommel, " Optics and Light," page 152.) If a piece of ruby glass is held in front of the slit of the spectroscope, all the colours of the spectrum disappear, except the red and orange. This effect shows that the ruby glass stops or absorbs the violet, blue and green rays of white light, and transmits only part of the yellow or orange and the red rays. If a green glass be taken instead of the ruby one, it will be found that the red and orange on one side and the blue and violet on the other side of the spectrum are blotted out or absorbed. The remaining part, which is green in this case, is called an absorption spectrum. When a ray of light strikes a solid body, it is supposed to penetrate through a minute distance, and to leave again at an angle similar to that described by a billiard ball striking the cushion and rebounding. This angle is called the reflecting angle, and is subject to fixed laws, the laws of reflection, which, however, cannot be defined here. It may, however, be briefly stated that a polished surface, such as a plane mirror, reflects the light regularly, keeping the rays closely together or parallel, whilst rough surfaces, such as snow or white paper, scatter the light in all directions. If white light illumines a body and all of it is again reflected, the body will appear white. If all the light is absorbed, the body will appear black. Snow reflects all the white light and therefore appears white ; black velvet absorbs all and appears a perfect black. A sea fog, which diffuses all .the white light, will probably form the purest white in nature. 15 If part of the coloured rays constituting white hght are absorbed and part are reflected, the body will appear coloured. The colour of the body is determined by those constituents of the white light, which being reflected, enter our eyes and excite certain changes in the " end-organs " of the retina. The remaining constituents of white light are retained or extinguished by the body. A red poppy will retain some constituents of white light, namely, violet, green and yellow, while it will reflect orange and red, which two reflected colours will give the poppy its characteristic scarlet appearance. A bunch of violets will absorb all the rays of white light except blue and violet. The colour of a body will be modified by the kind of light to which it is exposed. Let a poppy be exposed to light passing through a green glass, and it will appear black. This is caused by the red and yellow rays, which the poppy reflects under ordinary circumstances, being stopped by the green glass, whilst the poppy does not possess the property of reflecting the green which the glass transmits. No light at all will, therefore, be reflected from the poppy, nor excite our optic nerves under these peculiar cir- cumstances, and the result is blackness. A printer viewing a pale yellow print through a blue glass will, from the same cause, see the yellow print as if it were printed in black. Gas-light, which is deficient in violet rays, will modify most colours, particularly violet. THE THREE FUNDAMENTAL COLOUR SENSATIONS. The theory of the three fundamental colour sensations originated with Dr. Thomas Young in 1802, but was discredited and forgotten until 1853, when Prof. Helmholtz again brought it forward, and by his experiments added greatly to its probabilities. Soon after, J. Clerk-Maxwell first demonstrated pretty conclusively, by means of an ingenious contrivance of his own, called Maxwell's colour box, that there are really only three fundamental or primary colour sensa- tions namely, red, green and violet. If colours representing these three fundamental sensations are combined in proper proportions they form white light. Red and green combined form yellow. Green and violet combined make blue. Violet and red make purple, a colour not present in the spectrum. 16 Yellow (the combination of red and green) and blue (the com- bination of the violet and green) combined in proper proportions will also produce white light. To call red, green and violet " primary " colours may seem strange to those who are used to the primary colours of the artists, namely, red, yellow and blue, and knowing what effects their various com- binations will produce. However, what I have just stated about coloured light (for we are not now dealing with pigment-colours) can be proved, though perhaps not in the most strictly scientific way, by having three coloured circular glass slides to match, as nearly as possible, the red, green and violet of the spectrum. White light is projected throug-h these slides on to a screen by means of a lantern, and the coloured light discs moved until they partly overlap, as shown on the frontispiece. This experiment was shown upon the screen by Mr. F. E. Ives in his paper on the photo- chromoscope, read before the Royal Society of Edinburgh on January 17th, i8g6. The outer parts of the circles will show the fundamental red, violet and blue, the centre where all three overlap will be white or probably slightly grey owing to the impure colouring of the glasses. Where the red and green overlap yellow will be shown, where green and violet overlap cyan-blue, and where violet and red overlap a kind of pale crimson or magenta. COMPLEMENTARY COLOURS. Complementary spectrum colours are any two colours which, when combined, will produce white light. This can be brought about by suitable means, such as, for instance. Clerk- Maxwell's colour- box or Captain Abney's colour patch apparatus. Such pairs of complementary colours are purple and green, red and bluish-green, orange and blue, yellow and violet, etc. Such pairs, if combined, produce white light, and are therefore called complementary colours. It may here be stated that the primary colours and their secondaries of the artist's pigment-colours are not really comple- mentary, but "contrast colours." These will be fully dealt with later on. On these demonstrable facts the Young- Helmholtz theory of colour vision is based. This famous theory, which is now usually accepted as the best working hypothesis, briefly declares : — 17 -■'I. That there are three primary spectrum colours, red, green, and violet, which cannot be produced by any mixture of any other colours. 2. That there are three sets of " end-organs " in the retina of our eyes, one set being powerfully stimulated by red and orange rays, less so by green, and least of all by blue-violet ; the second set being especially excited by green light, and less so by the spectral rays on either side of it, i.e., red and violet. The third set are most susceptible to violet light, less so to green, and least of all to red. 3. That by stimulation of all three sets of "end-organs" (rods and cones) in nearly equal intensities we perceive white. The relative power of different spectrum rays to excite the respective fundamental colour sensations is shown by the curves in Koenig's diagram (modified and corrected by Captain Abney), which may be taken as the most correct. B C D E. F G H 2 -Sk ^ i- I 3 3 i I 2 I I G. 4. — abney's diagram of the three primary colour-sensation B TO H POSITION OF THE FRAUNHOFER LINES IN SOLAR SPECTRUM. * Dr. D. Fraser Harris on Ives' photochromoscope, in a paper read before the Philosophical Society of Glasgow, Nov. 6th, 1895. The fundamental green sensation cannot be perceived by the normal eye, but only by red or violet colour-blind people, for the reason that the red and violet sensations overlap in the green of the spectrum, as will be seen in the diagram of Koenig's curves. The colour-tone of the fundamental green sensation as purely as a normal eye can see it, is located between the Fraunhofer lines E and b, and may be taken as the primary green for purposes of colour mixture. The best representation of the fundamental red sensation lies between the lines C and D, nearer the former by two-thirds of the distance, and may approximately be represented by vermilion with a slight tinge of carmine. The best representation of the fundamental violet sensation lies between the G and H lines of the spectrum, and may be represented by deep ultramarine, which has been tinged with methyl violet dye. There are rays beyond the red and beyond the violet end of the visible spectrum. Those beyond the red end, the infra-red rays are caloric or heat rays, given out by heated bodies before they show incandescence, and these can be measured by an instrument called a thermopile. The rays beyond the violet end of the visible spectrum are called the ultra-violet or " actinic" rays. The complete spectrum consists of the invisible infra-red (heat) rays, the visible rays, and the invisible ultra-violet rays. These three parts are of about equal length. To the artist and colour printer however, only the middle, being the visible part, is of value. For the exact definition of a colour, three qualities have to be determined. The qualities are called colour constants, and are the following : — Hue, luminosity and purity. Hue is often called " tone." Hue is what in every day language is called the colour, for instance, scarlet, crimson, violet, etc. For scientific purposes the hue is referred to its proper location in the spectrum. Luminosity means the brightness with which a colour appears to the eye compared with a white surface, which is illuminated simul- taneously by the same white light. Purity means the freedom of a colour from admixture with white light. Tints reflect a great proportion of white light, and are diluted or impure colours. Pink is an impure crimson red, lavender is an impure violet. 19 PART IL PIGMENT MIXTURES. Primary Pigment Colours. Secondary Colours. Black and Grey. Tertiary Colours. Saddened Colours. Tints. Chromatic Clock Dial. Harmony and Contrast. Colour Combinations. Triads. PART II. ANY of the readers of this booklet, who have followed the brief outline of the principles of chromatics and par- ticularly the explanation of the Young-Helmholtz theory of colour vision, will probably ask themselves if the scientists who call RED, GREEN AND VIOLET primary colours, have wiped out of existence the notion of the three primary colours of the artists RED, YELLOW AND BLUE. This, however, on closer examination we shall find is not the case. Let us first remember that the scientist deals with coloured light, and in making mixtures adds one light to another, whilst the artist, by the superposition of pigment colours (if transparent), takes away more and more of the light reflected from the white surface on which he works. The scientist defines as primary colours those which cannot be produced by the mixture of any two colours of light, and which on the other hand cannot be further disintegrated. We must also recollect that if the three primary colours — red, green and violet — be combined in suitable proportions, they produce white light. It will be remembered that any colour sensation other than the primaries may be produced by mixture of two of the primary colour sensations in suitable proportions, with or without the addition of a certain proportion of white. The artist calls primary colours those which cannot be produced by superposition of any two transparent pigment colours. If the three primary pigment colours, red, yellow, and blue, be mixed in suitable proportions, they will produce grey to black, according to their density. Any colour may be matched by mixtures of two or three of the primary pigment colours, or by mixing two primary colours with a proportion of grey (i.e., diluted black) or white. 23 The artist calls secondary colours mixtures of two primary pigment colours. These secondary colours are supposed to be com- plementary colours of that primary colour which has not entered into the combination that makes up the respective secondary colour. This statement is, however, not strictly correct, as can be proved by experiment. The secondary colours of the artist ought rather to be called contrast colours of their primaries. For an explanation of the term complementary colours, refer to the first part of this book. The secondary colours of the artist are the primary colours of the scientist, red being obtained by superposing the transparent pigment yellow upon the transparent pigment red (a bright crimson), green by superposing the transparent pigment blue (cyan blue) upon the yellow, and blue-violet by superposing the bright crimson upon cyan-blue. It is, therefore, evident that although red seems to be common to both scientists and artists as a primary colour, the primary red of the scientists, i.e., the fundamental red of the spectrum, is quite different from the primary red of the artist. The fundamental red of the spectrum is similar in hue to vermilion, or, perhaps, a bright scarlet lake as made up by some artists' colourmen. This red produces good orange when mixed with yellow, but mixed with blue it produces only a dirty looking violet. It will also be impossible to produce a crimson by mixing small proportions of blue with vermilion, but scarlet can successfully be mixed from yellow and crimson lake (if the latter is not too purple). Let us take crimson lake in place of vermilion for the purpose of mixing violet, and we shall see that it produces a satisfactory violet, with cyan blue. We see now that crimson makes with yellow equally good orange as it produces good violets when mixed with blue, and that we cannot produce crimson by any mixture of two pigment colours. We, therefore, are justified in terming crimson a primary pigment colour. The correct shade of this crimson will scientifically be determined by a mixture of the red and blue-violet rays of spectrum, i.e., all the spectrum colours minus the green sensation. The crimson lake of some of the leading artist's colourmen is a very fair representation of this primary red of the artists. Using familiar terms, we may call the primary red of the scientist, "scarlet," and the primary red of the artist, "crimson." 24 The primary yellow of the artist may be defined as a combination of the fundamental red and the fundamental green of the spectrum, i.e., all the spectrum rays minus the blue-violet. The representative amongst pigments is what artists usually term "lemon yellow," a mixtureof chromate of zinc and chromate of barium, and which printers usually call "primrose yellow." Pale cadmium yellow also is of the same hue. This colour will produce good orange in combination with crimson, i.e., the primary red of the artist, and good greens with- cyan-blue (not violet-blue, such as ultramarine). The primary blue of the artist may be described as the combination of the fundamental green and the fundamental violet sensation of the spectrum {i.e., all the spectrum rays minus those of the red sensation). This is represented by some kinds of Prussian blue (ferric ferro-cyanide of potassium). Captain Abney, to dispel this confusion of primary colours of light and primary transparent pig- ment colours, has proposed that they shall be indicated by plus and minus terms. Thus, spectrum red is + R, spectrum green is + G, and spectrum violet is + V ; whilst the primary pigment red (crimson) is — G, the primary pigment yellow (primrose) is — V, and the primary pigment blue (cyan-blue) is — R. We have seen in the first part of this booklet that blue and yellow light produce white light, whilst the artist when mixing blue and yellow pigments produces green. How can this difference be ex- plained ? The fact is that the yellow pigment transmits both green Red Orange Yellow Green BUie Violet ■ Absorption of a typical Blue pigment Absorption of a typical YcllovV pigment III Green formed by the mixture of P>luc and Yellow FIG. 5. — GREEN FORMED BY THE MIXTURE OF COBALT BLUE AND YELLOW PIGMENTS. 25 Red Orange Yellow Green Blue Violet Ahsorptior\ of a topical Red pigment r III Absorpfion of a typical ■ ^^■■■■■11 Blue Violet formed bythemixtun of Red and Blue FIG. 6. -BLUISH-VIOLET FORMED BY THE MIXTURE OF RED AND BLUE PIGMENTS. and red, whilst the cyan-blue pigment transmits both violet and green. The green is, therefore, the only colour which both pig- ments transmit, and is the residual colour when they are superposed. The colours nearest the caloric end of the spectrum, the red and orange, will give us a sense of warmth, as will, likewise, their pigmentary representatives. Yellow, which forms the most luminous part of the spectrum, gives us a sense of light. A slight wash of gamboge over some parts of a water-colour landscape will produce a sunlight effect. The colours nearest the " actinic " part of the spectrum, the green blue, and violet, produce a sense of cold. Hence, when we hear artists speak of warm and cold lights and shades, warm and cold greys, we may infer that in the warm lights, shades, and greys, the red or orange preponderates, whilst in cold lights, shades, and greys, the green, blue, or violet preponderates. It has before been stated that crimson, yellow, and cyan-blue transparent pigments, mixed in suitable proportions, produce black, or if diluted with white a grey will result. Grey may also be defined as white deprived of part of its luminosity. All the constituents of white light are partly and equally absorbed by the body we term grey. A black pigment diluted with white will give a similar effect. If we mix crimson, yellow, and cyan-blue to produce black, it will be found almost impossible to mix the pigments so that a perfect dead black should result, that is, a black that will absorb all the 26 white light (except, perhaps, the sHght percentage which all blacks reflect). It will be found that our mixture, and also most of the carbon blacks, reflect a little orange or yellow besides this small percentage of white, and this orange or yellow will appear brown to the eye. The artists' colourmen and the printing ink makers are well aware of this fact, and try to counteract it by mixing a small proportion of blue with the black. Instead of diluting his black with white to make a grey, the water- colour artist utilises the transparency of his pigments, which allow the paper to reflect white light throught the paint. There are colours which are widely spread in nature, and are well represented by pigments, which are not seen in the spectrum but can only be imitated by partly abstracting luminosity. These colours are maroon, russet (terra-cotta), brown, citrin, olive, sage, myrtle, navy-blue, slate, and plum colour. These are broken hues and many people like to call them "art shades." They may be obtained by mixing pure colours with varying proportions of neutral grey. They are often called "tertiary" colours from the erroneous notion that prevails amongst artists that they can only be made up by mixing two of the "secondary" colours. A little reflection and experimenting will show that by mixing two "secondary" colours we really bring together the three primary (pigment) colours in more or less equal proportions, making up a black or grey which saddens the mixture of the two remainmg predominating colours. Thus we have accomplished, by a roundabout way, what can be done more directly by mixing grey with pure primary or secondary colours as the case may be. Another way of stating the matter is that saddened colours are hues deprived of their luminosity. Saddened red is called maroon. red-orange orange-yellow yellow yellow-green green blue-green brown. russet or terra-cotta. citrin. olive, sage, myrtle, blue violet purple slate, plum. navy blue. 27 CP Vermillion Scarlet 1^^ Cltrlae Stiaw FIG. 7. CHROMATIC CLOCK-DIAL, SHOWING COMPLEMENTARY AND CONTRAST COLOURS, PURE COLOURS, SADDENED COLOURS, DILUTED COLOURS, HARMONY AND CONTRAST OF COLOURS. [C. G. Zander's copyright design.^ 28 If we dilute pure hues with white we get tints which are also called by familiar names as follows : — Diluted red is called pink. ,, orange-red ,, salmon. ,, orange ,, buff, ,, orange-yellow ,, cream. ,, yellow ,, straw. ,, green ,, pea green. ,, blue-green sea green. ,, blue ,, azure. ,, violet lavender. ,, purple ,, heliotrope. ,, purple-red magenta. We may also mention two more familiar colours: — Drab, which is a grey in which orange slightly predominates, and French grey, in which blue slightly predominates. CHROMATIC CLOCK-DIAL. It will be useful to artists, colour printers, decorators, and, in fact, to all who work with colours, to remember which are contrast or complementary colours, as the case may be, and how to produce certain saddened colours or tints which may be required. As every- body is almost sure to have a watch or clock near at hand, it occurred to me that the clock face might be turned into a useful chromatic circle, and if once the position of the pure and broken colours be committed to memory, which should not be a very difficult feat, the}' may easily be called to mind in their proper position relative to the figures on the clock. I have taken Rood's excellent contrast diagram for a guide, but found it necessary to slightly modify the position of the colours so as to make them correspond more readily with the figures on the clock-dial, and to be remembered more easily. My chromatic clock-dial is intended more for practical every-day use than for scientific purposes. I placed yellow, being the most luminous colour of the spectrum, at the top at XII. of the clock, and as we proceed downwards to the right, the colours lessen in luminosity till we reach VI. (ultramarine blue), thence as we proceed upwards to the left through violet, purple, etc., the luminosity again increases till we reach yellow, our starting point. 29 Outside the pure hues I have placed the saddened colours, which may be produced by decreasing the luminosity of the pure colours, i.e., by the admixture of neutral grey pigments, whilst inside I have placed the names of the tints which may be produced by adding white to the pure hues. HARMONY AND CONTRAST. Harmony of colour may briefly be stated to exist between two colours which lie very closely together within a few degrees of the chromatic circle, or between two colours of the same hue but of different luminosity, the same hue either diluted with white or broken with grey. A glance at our chromatic dial will make the matter clearer. To give a few examples : — brown and orange will harmonise, so will pink and maroon, azure and navy blue, azure and pure blue, cream and amber, etc. Neutral grey will harmonise with any colour, although various effects are not equally pleasing. Hard and fast scientific rules cannot be laid down on this subject, which is more a matter of opmion and artistic taste. It may be remarked, however, that neighbouring colours of small interval, and of the same luminosity, should be separated by a neutral grey or black, or one of them should be of a different luminosity from the other. Contrast colours are hues which are far apart in the chromatic circle, i.e., more than go" or ^ hour of our chromatic clock-dial. Rood, alsoChurch, state that colours less than 80° or 90° apart suffer from harmful contrast. Contrast colours more than go° apart, help each other, and appear more luminous to the eye, although some combina- tions are not very pleasing but sometimes rather harsh. Scientific rules cannot be laid down for such combination, but only hints may be given. The further apart the two colours are, and the nearer the distance approaches 180°, or ^ hour on the clock, the stronger will be the contrast. When the distance reaches 180° they will be comple- mentary colours. Black and white also form a contrast. Likewise white with broken colours, though these combinations are not always pleasing to the eye. Black will always heighten the apparent luminosity of any colour which is surrounded by it; likewise, in a lesser degree, will grey, whilst white will lessen the apparent luminosity. 30 TRIADS. The combination of three colours to give an effect which shall be pleasing to the eye is more difficult to manage. Rood recommends at a distance of 120'', or about 20 minutes on our chromatic clock- dial, between the three colours. This distance need not be strictly maintained, as will be seen from the following combinations given by Rood: — Spectral red, yellow, blue. Purple red, yellow, cyan-blue. Orange, green, violet. Orange, green, purple-violet. Carmine, yellow, green. Orange-yellow, violet, bluish green. Scarlet, green, violet-blue. And others. The combination of triads will always look better if two of the three colours are warm ones and the third cold. One of the warm colours may be a broken one. A warm, pure colour combined with a warm and a cold tint will form a good combination, or two tints with either a pure hue or a saddened colour. Compared with continental cities, very poor taste is displayed in the colour combinations of the decorations used on festive occasions in this country. Hardly anything but the crude red, yellow, and blue is to be seen. The same may be said of theatrical and other posters displayed more liberally every day on the hoardings. I have seen some posters, printed in America, which showed excellent taste in their combinations of tints and broken colours of various gradations. I trust the few hints given here, which only touch upon the fringe of the subject of colour combinations, may be of assistance to British artists. Letterpress printers seem of late years to display more taste than formerly in their colour combinations in conjunction with some exquisite designs in type and ornamentation. There is, however, plenty more room for improvement in the display of artistic taste, and the scientific theory of colour combinations is well worth a serious study. 31 PART III. Three-Colour Work. Historical Sketch. Explanation of the principle of the Process. Action of the selective Colour- Filters. Production of the Red, Yellow, and Blue Blocks. PART III, pv^HE old saying' "there is nothing new under the sun" may be apphed to three-colour printing". Attempts to produce coloured prints by superposition of the three primary pigment colours were already made in the seventeenth century by German copperplate printers. This method was greatly improved in the eighteenth century by the addition of a black key- block. It needed, however, the assistance of photography, combined with a better knowledge of chromatics and spectroscopy, such as the end of the nineteenth century brought about, to enable printers to reproduce objects not only in their natural colours but in perfect contour and perspective with only three printings. J. Clerk-Maxwell first suggested the reproduction of natural colours by the superposition of the three primary colours of light, in a lecture delivered at the Royal Institution on May 17th, 1861. In 1865 Baron Ransonnet, of Vienna, and at the same time Henry Collen, the Queen's drawing master, had the idea of printing coloured pictures in three colours, by taking photographs of the objects by red, blue, and yellow rays and making superposed coloured prints from the resulting negatives. In 1868 two Frenchmen, Charles Cros and Ducos du Hauron published a similar idea of producing three-colour photographs. The first treated the matter theoretically, while the latter made practical experiments. They came nearer the true principle, but did not obtain satisfactory results. They proposed to print in red from a negative on which all the coloured rays except red had acted, in blue from another negative on which all the colours except the blue had acted, and in yellow from the third negative upon which all the coloured rays except yellow had acted. Further efforts were made in 1870 by Professor Husnik, at Prague, and Joseph Albert at Munich, both of which had the assistance and 35 advice of Dr. Vogel, of Berlin, and Dr. Eder, of Vienna. These attempts were more successful although the principle they worked upon was not scientifically correct. Dr. H. W. Vogel, of Berlin, in 1873, discovered that photographic plates could be made sensitive to various colours. However, for various reasons the application of his discovery did not for some time give the expected results. Mr. F. E. Ives, of Philadelphia, in 1881, was the first to pro- duce from three letterpress blocks a photochromic picture, using single line screens similar to what are being used at the present time. Later, Dr. Vogel's son, Dr. E. Vogel, in conjunction with a lithographer, Ullrich, of Berlin, produced photochromic pictures which were exhibited at the German Exhibition in London, in 1891. The system they worked on, however, necessitated the addition of a grey tint, which is not necessary if the process is carried out on strictly scientific principles. During the last few years Messrs. Husnik & Hausler, of Prague, have produced some beautiful blocks for three-colour typographical work; and quite recently the Heliochrome Company, Limited, 122 Elgin Crescent, Notting Hill, London, have made some splendid blocks for three-colour work. Before explaining the principles of photochromic three-colour work it should be mentioned that this process is adaptable not only to letterpress work by means of half-tone blocks, but also for collotype and lithography. Collotype gives the most delicate results, but at the same time is the most difficult to work. For commercial purposes the half-tone blocks reign supreme at present. The principle of photochromic three-colour work is based upon the Young-Helmholtz theory of trichromatic vision. In Part I. it was explained that the colours of all objects can be reduced to three primary colour sensations (red, green, and violet), and with these we can form white light and all possible colours of nature, including tints and saddened colours (or aesthetic shades, as some people like to term them). Three selective colour filters, interposed between the lens of the camera and the sensitive plates will produce three photographs which when viewed simultaneously through the pure colour filters will stimulate the end organs of our eyes in such a way as to reproduce a mental image of the natural colouring of the object. 36 On this principle is based Mr. F. E. Ives' marvellous invention, the Photochromoscope. This instrument will produce a mental image of objects in their natural colours and perspective by viewing the three monochrome photographs simultaneously through pure colour filters, red, green, and violet. To quote Mr. Ives' own words (jfoiunial of Society of Arts, May 27th, 1892): — "By photometric measurement of the density curve of a spectrum negative, the relative amount of action by different spectrum rays may be found. It is therefore only necessary, in order to secure action by different rays in any definite proportion, to use such a combination of sensitive plates and colour screen as will yield a spectrum negative having a density curve corresponding to the graphic curve representing such proportionate action." The proportionate action of different spectrum rays in the respective negatives would be as indicated in the curves in Koenig's diagram if the green of the spectrum was not itself a compound sensation colour. But for this reason it is necessary for this purpose to regard the purest spectrum green as a primary colour, and make the measurement for density curves accordingly. That is what Maxwell did, and Maxwell's curves, although not the true sensation curves, represent the correct proportionate action for the different rays in the photographic process. ABC D E F G H \ GR BL. FIG. 8. — DIAGRAM OF J. CLERK MAXWELL'S CURVES OF THE THREE PRIMARY COLOUR SENSATIONS. If the sensitive plate was acted upon like the eye, the photo- graphic screens should transmit the various rays in the proportions 37 shown by the form of the respective curves in Maxwell's diagram ; but allowance has to be made for the different relative colour sensitiveness of the photographic plates, and for that reason a set of screens that is right for one kind of plate will be all wrong for another. For instance, a yellow screen will give nearly all the action in the spectrum green on an Edwards' Isochromatic plate, and nearly all in the orange-red and yellow on a Lumiere series B plate. It is evident that if one were right, the other must be all wrong. It is obvious that the production of perfect colour filters requires the employment of a photo-spectrograph by an expert. But a close approximation to the best results can be got by using an aurantia screen with a Lumiere series B plate for the negative of the red sensation (printing colour for block, cyan blue), a lighter screen of the same material with a Lumiere series A plate for the green sensation negative (printing colour for block, crimson), and a screen of pale chromium green glass with an ordinary plate for the negative of the blue-violet sensation negative (printing colour for block, yellow). For the purpose of reproduction by colour printing, positives are made from the negatives which record the three-colour sensations, and from these positives, if we use the typographical method of printing, half-tone blocks are made. Each block is then printed in the transparent pigment colour which represents the combination of the two colour sensations stopped out by the colour filter which was interposed when taking the negative. As stated in Part II., all colours can be matched by mixtures of the three primary pigment colours, including greys and black. The three primary pigment colours in which the three colour blocks just mentioned should be printed are therefore perfectly sufficient to reproduce the natural colours of any object as far as this is possible b\' means of the pigments which modern chemistry has placed at our command. We cannot here enter into the details of making half-tone blocks, neither can directions be given how to make colour filters. Suffice it to say, that some colour filters are made of coloured glass, others consist of glass troughs constructed of two parallel sheets of glass, sealed all round and holding in the intermediate space a coloured hquid. This liquid generally is a solution of an aniline dye of the requisite shade. 38 Amongst the filters now on sale none are correct as far as I know. Experiments are being made at present to produce sets of colour filters of coloured gelatine and also of glass plates covered with collodion films dyed with aniline dyes. So far, however, none of these are on the market. The success of photochromic printing in three colours depends of course in a very great measure on the inks, which like the colour filters permit of no arbitrary selection or groping in the dark. Their colours, as no doubt it will have been inferred from what has been explained, are determined by fixed scientific rules. For that reason I thought it fit to devote a separate chapter to the description of the properties of the inks. 39 PART IV. Half-Tone and Photochromic Printing Inks* PART IV. LTHOUGH it is intended to deal principally with photochromic printing- inks, a few remarks on half-tone inks in general may be useful. Of late years so-called "art shades," i.e., reds, greens, blues, violets, and purples, subdued or saddened with a small percentage of black, have deservedly come into favour alike with the public and the printers, and particularly so since some of the illustrated papers issued supplements of reproduc- tions of Royal Academy pictures, and other subjects, printed in these subdued colours. These art shades look very effective if used in the production of artistic commercial stationery, illustrated catalogues, menus, etc. The effect, if these broken colours are judiciously selected, is very pleasing, and many of them give half-tone printings the appearance of two shades, as if produced by two printings. Tints of various colours may with great effect be combined with these saddened hues, and I have endeavoured to give a few hints for such combinations in Part II., when speaking of the harmony and contrast of colours and the combination of triads. For half-tone work only the very best inks should be used. The blocks on account of their flat surface take very little ink in com- parison with woodcuts or type, and therefore unless the ink is made of strong pigments, or the finest carbon black, the prints will turn out flat and look washed out. Natural earth colours, such as umbers, siennas, ochres, terra-verte, etc., should be rigidly rejected, for no amount of grinding will alter their hard and gritty nature, or make them fit for the production of delicate half-tones. They also cause unnecessary wear to the fine grain of the blocks, and are only desirable for ordinary letterpress or litho-printing on account of their cheapness and the variety of browns they comprise. For half- tone work all the hues of the earth colours may be produced from more suitable sources, and the printer who is desirous of turning out good work, should not mind paying a little more for better inks. 43 Any shade of brown may be made of black and red (madder being the best on account of its great strength and permanency) with or without the addition of yellow or blue. In this way an excellent brown, imitating silver prints, may be mixed. Green-blacks, olive- greens, nut-browns, and other shades, may be produced from madder, Prussian blue, and black, without havmg recourse to earth colours, to which white should be added for diluted colours. The theory of pigmentary mixtures has been dealt with in Part II., and the chromatic clock-dial may be consulted with advantage. The mixture of such art shades should however only be undertaken by those who are well acquainted with the idiosyncrasies of the pigments they are using, otherwise they will only waste time and materials and temper. It will in all cases be found more satisfactory to entrust the printing ink maker with the matching of the pattern. The proportion of black necessary for the production of subdued colours is very small on account of the fine division and consequent colouring power of the carbon. It will probably not exceed 5% to 10%, varying with the tintorial value of the other pigments. The latter being in great preponderance should be of the best possible quality. Good lakes, i.e., dyes precipitated on an earthy base, such as hydrate of alumina, are most suitable for the purpose. These distribute well, print even, and do not fill up the interstices between the dots forming the half-tones of the block. On account of their strength and bulky nature, such lakes will be found cheaper in the end in spite of their higher price than earth colours. They will save labour m doing away with frequent washing up, and they will not wear the blocks. Excellent lakes of all colours are now produced from aniline dyes, and may with advantage be used where permanency on exposure to light is no object. But if permanency be desired, alizarine lakes made of alizarine, which, like aniline, is a coal-tar product, should be employed. It is also found in nature, as the colouring principle of madder-root, which used to be extensively cultivated in the south of France. Our modern artificial madders are perfectly permanent even in tints, and can now be produced in all shades of red, from scarlet to purple, and in excellent imitations of car- mine and cochineal crimson and scarlet lakes. They form a very desir- able base for half-tone inks, and should be used by the conscientious printing ink maker for the red in photochromic three-colour printing. More about this later on. Ultramarine is a most undesirable pig- 44 ment for half-tone inks, as it does not print flat, and it is particularly unsuitable for photochromic printing;- on account of its opacity. With these few introductory remarks upon the quality of process printing- inks, I now come to deal with photochromic inks used for three-colour work. The success of photochromic work depends on the blocks, on the inks, on the prmter, and in a certain degree also on the paper. I am going to speak of the ink only, and therefore take it for granted that the blocks are produced by colour-filters con- structed on scientific principle, i.e., with a thorough knowledge of spectroscopy and photography, and not chosen in an arbitrary way. I have dealt with this subject in the preceding parts of this book. Further, I must take it for granted that the printer does his part ot the work not in a purely mechanical style, but that he has at least some knowledge of the principles of three-colour printing, the lack of knowledge of which is at present a serious stumbling block in the way of the success of photochromic printing. One of the crucial tests of good photochromic work is the production not only of a correct rendering of the colouring of the original, but the production of neutral blacks and greys wherever they occur in the original, be it a painting or still-life object. If the colour-filters are correct representatives of the primary colour-sensations of the spectrum, the three negatives or chromograms will be monochrome representatives of the excitations caused on the end organs of our eyes by each of the respective primary colour-sensations reflected from the object. It is necessary in order to obtain a correct rendering of the tintorial representation in print that the positives, i.e., the blocks, should be printed in inks which are complementary colours of the colour-filters used. It is obvious, therefore, that as the colours of the three selective screens, if scientifically constructed, are — if I may use the term — a fixture, so the three pigmentary colours used in printing are also a fixture, and cannot be arbitrarily selected. Here the carelessness, indifference, and ignorance of most printing ink makers has been and is still causing great mischief and bringing ridicule upon one of the most interesting achievements of modern science. I have from time to time examined samples of photochromic inks of various makers, and found they all differ more or less, not only in the shades, but in the strength of the pigments used in their manufacture. Some makers unscrupulously use fugitive aniline lakes for the red, which, after a few days' exposure to light will fade 45 and render the colouring of the whole picture incorrect. The three pigments which alone produce a correct colouring of a picture produced by the photochromic process, are a pure red pigment, one that is neither a purple nor an orange, but is the primary red of the artist, i.e., the combination of fundamental red and blue-violet of the spectrum, as explained before. The yellow ink must be a pure yellow, not inclined either to orange or green, i.e., about the shade of sulphur, or what artists' colourmen call " lemon yellow." The third ink, the blue, must be cyan-blue, somewhat similar to a greenish cobalt blue. Neither the violet nor the green should, how- ever, preponderate in this blue. If these three inks are correctly made, it will, by their mixture, be possible to produce every colour, including tints, saddened hues, and dense blacks. The tintorial mixture in a photochromic print will be two-fold, optical and pigmentary. Those acquainted with half-tone work know that the shades, tones, and half-tones in a picture are produced by dots of various sizes, the smaller producing the lighter parts of the picture, and the larger the shades and outlines. Now in a photochromic picture, the various colours are produced by the superposition of yellow, blue, and red dots of various sizes. Wl]ere these dots cover each other they produce a pigmentary mixture, almost identically as if the pigments had been mixed by a palette knife previous to being printed. Where these dots lie next to each other they produce an optical mixture, that is, the eye will record two adjoining dots simultaneously, for instance, red and blue appear as violet; blue and yellow as green; red, yellow, and blue, i.e., the three colours combined, as black (or grey if the dots are small and allow the paper to reflect white light through between the interstices). These remarks now lead us to the second essential quality of the photochromic inks, viz. — transparency. Unless the pigments used are transparent, the pigmentary mixture just alluded to cannot take place. Wherever, for instance, an opaque red dot should cover a yellow one, instead of producing an orange or scarlet it would only show the colour last printed, but if the red is transparent it will combine with the yellow to form orange. It is not very difficult to find a red that answers not only to the required shade but possesses transparency; we find it in madder lake, struck on a transparent base such as hydrate of alumina. This pigment possesses another valuable property, that of absolute permanency when exposed to 46 sunlight. The blue pigment is more difficult to produce. The best is a cyanide blue, which can be made of the requisite shade, and is transparent. It cannot be called absolutely permanent, but the fading when printed full strength is so slight that it need not be taken into consideration. Artists do not hesitate to use this blue in the most valuable pictures. Ultramarine, as I have stated before, must be rejected on account of its opacity, and aniline blues are much too fugitive. The most serious difficulty presents itself in the selection of the yellow and only very recently after a great many experiments I have found a transparent yellow lake which promises well for permanency. It is of the requisite shade and perfectly transparent. Up to now this non-success of producing a permanent transparent yellow necessitated the use of an opaque pigment and printing the yellow first. If that is done it does not matter if an opaque yellow pigment is used so long as it is permanent and of the requisite shade. It is also advisable to print the blue last on account of its possessing the smallest luminosity. But for these two reasons, it would not matter in what order the colours are printed. So it is necessary to print them in the order of yellow, red, and blue. I need hardly mention that it is also of great importance that the pigments should be well proportionate as regards their colouring power. If that is not so, it will be found that the strongest pigment causes the picture to be coloured with a preponderance of that particular colour, which is generally the red. Placed in Lovibond's tintometer it will be found that the yellow and blue pigments are of about equal strength (about seventeen units each), whilst the red pigment, if madder, will measure probably thirty-four units, or about double the strength. It is, therefore, necessary the printing ink maker should proportion the strength of the pigments if correct colouring of the picture is to be expected. This is a matter which I find is almost always ignored. What I have said about photochromic printing inks will be sufficient to prove that great attention to details is required in the manufacture of these inks. The selection of pigments, suitable not only as to shade but also as far as their permanency, transparency, and tintorial strength is concerned, must be a matter of great care and experience. They require far more care in grinding than ordinary inks, as from this cause variations in shade would cause serious differences in the colouring of the prints. 47 Although not falHng under the heading of " Photochromic Printing Inks," I feel bound to make a few observations about the paper. If you take a pigment — madder lake, for instance — and rub it up either in plain water or gum water, and paint it on a sheet of hard, well-sized, and glazed paper, you will get a bright red, owing to the smooth surface of the paper reflecting some white light with the pigment, making the latter appear bright. Now take a sheet of white blotting paper and paint it with the same colour, the result will be a kind of dirty maroon or claret colour. The blotting paper absorbs some of the light which the glazed paper reflects. The lesson is obvious — use good paper only, hard, well-sized, and glazed, and in printing use hard packing, eight or ten sheets of cream wove paper. It will then not be difficult to print from blocks of very fine grain, and the colours will appear much cleaner and brighter. No pains should be spared, either, in the making ready of the blocks. Thus with blocks made from scientifically constructed colour- filters, inks of correct hue, good paper, a knowledge of the principles of photochromic printing, combined with a little enthusiasm, which this new scientific way of colour-printing well deserves, we may expect to obtain as good results as are possible at the present state of photo-trichromatic printing. 48 Warehouse: 15 Whitefriars St., LONDON, E.G. Fine Colour Department: loi Leadenhall St., London, E.G. A, B. FLEMING & Co.. LIMITED. Scottish Printing Ink Manufactory, Caroline Park, EDINBURGH. Established A.D. 1852. . . Manufacturers of every kind of BLACK and . COLOURED 3nh6 == s HALF-TONE PRINTING INKS in Black and Art Shades a speciality (any shade made to order). Our Half-tone Inks will not fill up, do not contain Earth-Colours, and are permanent. PHOTOCHROMIC PRINTING IN THREE COLOURS . . . The three Neutral Colours (Yellow, Red, and Blue) specially prepared, and guaranteed absolutely permanent. High'class COLLOTYPE INKS of all shades. 49 A. B. FLEMING & Co., Limited, Scottish Printing Ink Manufactory, Caroline Park, EDINBURGH. ONE OF THE OFFICES, CAROLINE IWRK, EDINBURGH. The three Half-tone Blocks illustrating A. B. FLEMING & Co.'s Offices and Works were supplied by ... . W. H. WARD & Co., Limited, Holbein House, 119 Shaftesbury Avenue, LONDON, w.c. VIEW OF ONE OF THE GRINDING SHEE)S AT CAROLINE PARK WORKS. EDINBURGH. THE INKS Used in printing this book were manufactured by H. 3B. Jf leming 8i Co.. Ltd., CAROLINE PARK, EDINBURGH. . . PHOTOCHROMIC INKS .... Made on scientific principles a speciality. Printed by Allen & CarrutJiers, The Cranford Press, Chisiuick, W.