The theory of color in its relation to art and art-industry

Front matter

THE

THEORY OF COLOR

IN ITS RELATION TO

Preface To The American Edition

the English version in all its parts offers a perfectly correct rendering- of the ideas of the original.

There is one point, however, which I should here like to dwell upon somewhat more at length, i. e. the choice of terms for the designation of some of the colors. Peculiar difficulties had to be overcome in this respect, even in the German language, since several of the names, which are familiar to the physicist, are entirely unknown to the artist, while dyers and weavers employ still other designations, which are again different from those used by either of the two classes first named. I therefore resolved to depart from the usages of physical terminology in a few instances in which this terminology would be likely to give rise to decided misunderstandings, and I cannot refrain from expressing a strong hope, that these changes may be sanctioned and adopted by my colleagues in the profession. It seems well, at all events, to call attention to these changes here, and to give a concise statement of the reasons which induced them.

The first relates to the replacing of the term " indigo" for a part of the spectrum by " ultramarine," as this latter pigment is much better fitted to represent the corresponding spectral color.

Again, I have replaced the term " cyanogen-blue," which, as far as I know, originated with Helmholtz, by the term "turquoise-blue," as the former would necessitate a special definition, while the latter is perfectly clear to all those who have once seen the half-precious stone in question.

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PREFACE TO THE AMERICAN EDITION.

If such difficulties had to be met in writing the book, even in the mother-tongue, it is but natural that they should assert themselves still more decidedly in the translation into a foreign language. The word "purple," for example, is employed by English as well as by German physicists to designate a hue which is situated between red and violet. The German artists likewise use the word in the same sense, while no definite idea whatever attaches to it in ordinary usage. In English, on the contrary, " purple" is generally understood to designate a color which other nations, and also the English physicists, call "violet," and the second, original meaning of the word has only been preserved to a certain degree in the "royal purple" of the poets.

The modern art of the dyer has a variety of names for the different shades of this color, all of which shades can be most beautifully produced by combinations of aniline, and which are known to commerce as "Magenta-red," " Solferino-red," " Garibaldi-red," etc.; but all these designations are too much exposed to the caprices of the everchanging fashions, to make it desirable to adopt either of them in place of the word " purple." The term " crimson," which is sometimes used for these hues. by artists, also appeared to be too indefinite, especially as in German crimson, or carmoisin, has a meaning which is different from that attaching to carmine.

The word "purple " has therefore been retained,

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PREFACE TO THE AMERICAN EDITION.

and has been used throughout in the sense in which it has become naturalized in physics.

Similar difficulties made themselves felt in a number of other cases, and I must therefore urgently request my readers, for the sake of securing a clear understanding, to pay special attention to those passages in which it has been attempted to define with scientific accuracy the somewhat loose terms commonly in use.

As to the leading ideas which have served as a guide in the construction of the whole work, I have already expressed myself in detail in the preface to the German edition. I will therefore confine myself to adding that, in regard to the experiments described, I have followed a principle which differs entirely from that usually followed in modern popular works on science. For while in these works there will generally be found descriptions of brilliant exhibitions, which have been given at great cost before vast audiences, it has on the contrary been my desire as much as possible to bring all experiments into a form which will admit of their being repeated even by the unprofessional reader, and with the most simple materials.

Nothing now remains to be done by me, but to give utterance to the wish that the reception accorded to the book may correspond to the careful labor bestowed upon it by the translator as well as by the publishers, for the purpose of making it accessible to the Anglo-American public.

THE AUTHOR

PBEFACE.

MOTTO :

LlONAEDO DA VlNCI.

THE author does not conceal from himself the fact, that the book which he is about to offer to the public will have to encounter a widespread prejudice, more especially among those for whom it is principally intended.

The opinion is frequently met with, that the most glorious creations of the fine arts owe their origin almost exclusively to' an inborn talent, which has been developed by long-continued practice ; while, on the other hand, it is believed that scientific investigations into questions of art are of but small value to true genius, and that, at the very best, they can only help mediocrity to attain to achievements of questionable merit.

Curiously enough, history teaches us that the most prominent artists did not share this opinion. The great heroes of art, those men whose works betray a master's hand in every line, exerted themselves most zealously to replace purely instinctive effort by consqious activity, and to inquire into

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the causes which underlie all successful creative production. Although nothing was more foreign to tliem than the idea that technical skill must be looked upon as the ultimate aim of their studies, they nevertheless neglected nothing which appeared to be calculated to make them thorough masters of their craft. And for the purpose of reaching this aim they were quite as earnest in devoting themselves to scientific studies, as they were well assured that the perfect control of all outward aids is absolutely necessary, if the emancipated intellect is to be enabled to soar to the highest realms of art without being hindered by petty limitations.

To prove the truth of the assertion just made, it will be sufficient to recall the names of Lionaedo da Vinci, of Albeecht Durer, and of Rafael.

Lionardo made anatomy and perspective the subjects of his study, and was one of the first to devote considerable attention to color. His investigations in these departments are so thorough and so important, that an enduring place is secured to his memory in the history of science. Durer wrote on geometry, not to speak of his work on fortification, since this latter has no connection with his artistic activity. And even in the case of Rafael, who may be taken as a pre-eminently fitting example of a genius "by the grace of God," the evidence is not wanting which proves that he did not regard severe scientific study as superfluous ; for sketches by him are still extant, show-

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IX ing the figures which in his large paintings appear draped, not only naked, but even as skeletons.

Since the days of these great men the conviction has taken root, that no artist can get along without a knowledge of anatomy and of perspective.

It is different, however, with the theory of color. The attempts made to build up this theory, as applied in art, upon a similarly secure basis, and to place it alongside of the other two sciences, as their peer, have not, so far, been very successful.

To be sure, it cannot be denied that, from the very start, these three sciences occupy a somewhat different position in relation to art. While it is simply impossible to paint a tolerably decent picture without a knowledge of anatomy and of perspective, masterpieces of color and exemplary ornaments were produced at a time when a theory of color, based upon scientific principles, could not be thought of.

Nevertheless, the works of prominent colorists show a very consistent application of certain expedients, and it does not admit of a doubt that these masters had formulated, at least for their own use, fixed systems for the treatment and the application, of color, which may perhaps have been handed down as traditions to their personal scholars, but which others can only reconstruct with difficulty from their works.

Such systems cannot become common property, unless it should be possible to give to them a scientific expression.

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X PREFACE.

But in appealing to bygone times, we must take good care not to forget that the position occupied by art to-day is different from that which it formerly held. As long as art — which must here be understood as likewise embracing the art-industries — is in a condition of steady and quiet development, the individual artist may in a measure be looked upon as simply an interpreter of the many. He gives expression to the ideas and to the efforts which animate all of his surroundings ; he is held up and led on by the feelings and the taste of his nation and of his age, which develop themselves in accordance with an inner necessity. The iron logic of history and the healthy common-sense of the people as a whole, which it is so exceedingly difficult to repress, guard him from grave errors ; while on the other hand, in times of decay, they are quite as inexorable in forcing him to follow the current.

Different conditions, however, assert themselves in our own day, in which the rapidly growing means of intercommunication throw the productions of all nations and of all schools promiscuously upon the market; in which the increasing historical interest brings to light the works of art of past periods, and compels everybody to make himself familiar with them ; and in which the spirit of invention, incessantly working in feverish haste, is continually producing new tools and new materials, before those which have hardly been acquired have had time to be thoroughly

PREFACE.

XI comprehended and artistically applied. Under such circumstances it is necessary to call in the aid of a judgment refined by science and quickened by severe thinking, if taste is not to be led astray, and the feeling for the truly organic construction of a work of art is not to be stifled by the impressions rushing in from all sides.

The best evidence of the truth of the assertion just made — i. e. that theoretical studies are to-clay of far greater importance for art than formerly — is furnished by architecture. "While magnificent works were produced in past periods by masters who hardly had any idea of the history of art, it is absolutely impossible at present to conceive of any great architectural achievement without a thorough preparation in this branch of knowledge.

But, aside from the influence which all studies of this kind — including, of course, studies on the effects of color — must exercise upon the education and the purification of the artistic feeling, it is also to be considered that, from purely technical motives, and especially on the part of the art-industries, it is often felt to be desirable to possess the results of experience in a well-defined and fixed form. This is more especially true of those branches of art-workmanship which are compelled to employ colors that have been fixed upon beforehand, such as the weaving of colored stuffs, for instance, or the manufacture of paper-hangings, chromolithography, and similar art-industries. In problems of this

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class the artist does not enjoy the same liberty as in painting. It is denied to him to approach nearer and nearer to the picture which may be present to his mind, by minute changes in the hues of the colors, introduced during the progress of the work ; but he must, on the contrary, know to a certainty from the very beginning what effect the chosen colors will have when combined together in the shape of a work of art. Even by the use of a painted sketch this difficulty can be obviated only to a very small degree. For, on the one hand, we are especially subject to great delusions in judging of the colors composing a certain pattern, which delusions can only be avoided by varied experience or by scientific knowledge ; while, on the other hand, the use of a new material will also be the cause of new effects of light, so that the colors will appear to be considerably changed if the same pattern is executed in the same hues, at one time in wool, at another in silk, or whether the fabric selected be velvet or satin.

And, indeed, the first attempt of any importance to produce a practical theory of colors was induced by art-industry ; for the celebrated chemist Cheveeul, who undertook this task, was prompted to it by his situation as chief of the manufactory of Parisian gobelins, owned by the government of France. It became clear to him. that the complaints of the workingmen about the performances of the dyeing establishment connected with the manufactory were really not to be laid at the door of this

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xm establishment, but that they had their foundation in the apparent changes which the colors underwent when in juxtaposition with others, i. e. in so-called effects of contrast. Chevreul therefore characterized the whole of his work as the theory of " simultaneous contrasts"

The great extent which these apparent changes of colors in juxtaposition can assume is well illustrated by an incident cited by Chevreul. A merchant and a silk-weaver were involved in a lawsuit, which owed its origin simply and purely to such an effect of contrast. The merchant had delivered black silk and blue silk to the weaver, which was to be made into ribbon. After the delivery of the ribbon, the merchant insisted that the silk had been exchanged, as it was of a brownish black, while that given to the weaver was of a deep black. The merchant, however, wronged the weaver completely, for the change in the silk was only apparent, having been brought about by the juxtaposition of the blue, and, in addition to this, strengthened by the peculiarities of the web which had been chosen.

The investigations of Chevreul were received with the greatest interest by the French manufacturers, so much so, that the Chamber of Commerce of Lyons prevailed upon him to write a special treatise on the optical effects of silken fabrics, — a proof, well worthy of being taken to heart, that the French manufacturers do not rely simply upon their innate taste for the art-industries, but that they seize

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with avidity upon everything calculated to aid their efforts in this direction.

But, however valuable Chevreul's works on the theory of color may be, they treat too exclusively of the effects of contrast on the one hand, while on the other they are the offspring of a time when the nature of the mixture of colors was as yet too little understood to allow of the idea of constructing a system of color upon a secure basis.

Such a construction became possible only after the pioneer investigations of Helmholtz had made clear the difference between the mixture of colors and of pigments, and after he, as well as Maxwell, had fixed the laws of the true mixture of colors by the aid of convincing experiments.

The physical and the physiological side of the theory of color had first to be sufficiently developed by these investigations, before it could be made available as a basis for practical aesthetic inquiries.

An attempt of this kind was made ten years ago, by Brucke, in a work which he entitled "The Physiology of Colors," and in which he digested all the material at hand, while at the same time he enriched it by a great many subtle observations and highly interesting remarks. But in spite of its merits this work has penetrated but little into the sphere for which it was especially intended, and another similar attempt may therefore be justifiable.

This is the aim of the present work. It is

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xv intended to make artists and persons engaged in art-industrial pursuits familiar with the results of investigation, presented in the simplest possible form, and it is to show how the various propositions which have been laid down may be made available, either in the creation of new works, or for the comprehension of those already existing.

Accordingly I have presupposed no knowledge whatever in physics, but have endeavored to present a whole that shall be complete in itself, and have chosen a manner of treatment which will be easy of comprehension to every person of education.

In this endeavor I was materially assisted by the publisher, who met all my wishes in regard to wood-cuts and plates with the greatest readiness.

The leading principles in the first four chapters are of a purely physical nature ; but the illustrations, as well as the materials necessary for the experiments, have been selected as much as possible from the sphere, both ideal and practical, in which artists are accustomed to move. This appeared to be necessary for the purpose of continually keeping in view the close connection of the statements made, and of the experiments described, with the special activity of the artist.

Such a treatment naturally demanded a pretty thorough, independent manipulation of all the scientific material bearing upon the subject, so that the book will probably not be devoid of interest even to the specialist, although, from the

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very nature of its tendency, it is not devoted to severe scientific investigation.

Many readers will perhaps be loath to miss all attempts at a critical estimation, and a refutation, of Gothe's theory of color. The author preferred, however, principally from a feeling of veneration for the great poet, to let the facts which have been brought to light by rigorous scientific research speak for themselves, instead of entering upon the critical examination of a work which never exercised any lasting influence upon the development of science, and which has been excellently well refuted long* ago.

An essential difference will be noticed between the first four chapters and the last chapter. While the contents of the former are largely of a physical and physiological character, the fifth chapter will be found to be principally devoted to the artistic and the art-historical aspect of the theory of color.

In regard to this point I must, however, most urgently entreat all specialists to be lenient with me; and I must lay especial emphasis upon the fact that I am neither a professional student of aesthetics nor an art-historian, and that I have never had the opportunity of making thorough literary studies in these branches. My knowledge and my judgment in matters of art I owe almost exclusively to the collections of my native city, Munich, and to the intercourse with the artists whose friendship I enjoy.

I was nevertheless compelled to venture the

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xvii attempt to penetrate into this to me somewhat foreign department, as it was the only possible means for bringing to a close the chain of individual investigations, and for showing the practical and aesthetic importance of the propositions in physics which had previously been developed.

Those readers, therefore, to whom the physical investigations may at first appear to be rather unattractive, will do well to begin with the last chapter, deferring the real study of the book until they have themselves felt the want of a secure basis.

The aim and the scope of the work have undoubtedly been sufficiently characterized by what has been said above. It is intended to connect, by an intellectual chain, the mass of isolated observations which every artist must make, and continues to make daily ; to awaken and to intensify the interest in, and the feeling for, color ; and to increase and to purify the comprehension of its importance in art.

May the book everywhere succeed in awakening

the same interest in its subject which called it into

being !

THE AUTHOR.

Introduction

THE phenomena of Light are now commonly explained by the Undulatory Theory. This assumes that all space is filled by a medium called ether, almost infinitely more rare than the most attenuated gas, and that the passage of minute vibrations through this medium gives rise to the effect which we call light. The motion of the ether is at right angles to the direction of the light, so that when the sun is overhead the motion of the ether is horizontal. Such vibrations, like the waves of water, are said to be transverse. The intensity or brightness of the light is dependent on the amount of motion of the ether, or height of the wave, while variations in the length of the wave give rise to the phenomena of color. The key to the best method of studying the laws of color was found by Newton when he showed that the prism was capable of decomposing light into its primitive colors. It thus appears that a beam of sunlight, instead of consisting of a simple system of waves, is really composed of a collection of rays of an almost infinite variety of wave-lengths. When the longer waves fall on the retina they produce the sensation which we call red. As the waves gradually diminish in length, we obtain in turn the effect of yellow, green, blue, and violet. Bays of greater and less length than these are also commonly present in white light, but as they do not affect the retina they are invisible. Other means must there-

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fore be employed to detect them. A blackened thermometer bulb readily absorbs the longer waves and serves to mark their presence, while it is but little affected by the shorter waves of green, blue, or violet light. On the other hand, a sensitized photographic plate is but little changed by the longer red rays, but quickly alters under the influence of the blue or violet waves. Formerly these effects were supposed to be due to three different kinds of waves, those of light, heat, and chemical action. There appears, however, to be no real difference between them except in degree, and the light, heat, and chemical action should rather be regarded as three manifestations of the same power, which is sometimes called radiant energy. A proof of this is found in the fact that if we employ light of uniform wave-length, as the flame of a spiritlamp with salt on its wick, we find that, however we alter its brightness, the heat, light, and chemical action all alter in the same proportion. If now we use a beam of white light, this rule seems no longer to hold. Tor instance, by a plate of clear glass, or better, by a thin layer of water, we may cut off a large portion of the heat while the light is affected but little. Again, interposing a plate of blue glass will diminish the liwht.and heat far more than the chemical action. The

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explanation is, however, quite simple. In the first case, the glass cuts off in a great measure the waves of length greater than the red, to which the heat is in a great measure due. These rays are, however, invisible, and therefore their removal is not perceptible to the eye. In like manner the blue glass transmits the very short waves which affect the photograph, but which are invisible, while it cuts off the red and yellow rays to which the sensitive plate does not respond. If now the light is analyzed by a prism, we shall find that for each color the heat, light, and chemical action are reduced in the same proportion. Thus if the blue glass cuts off nine tenths of the light of the red ray, it will also cut off nine tenths of its heat and nine tenths of its chemical action, and

INTRODUCTION.

xxi the same law holds true for the other colors. While there is this simple relation as regards rays of any one wave-length, it is quite otherwise if we compare the rays of one color with those of another. There is no known method by which we can measure the relative brightness of different colored lights ; and while we may compare the temperature of a thermometer exposed first to one ray and then to the other, such a measurement will not properly represent the relative amounts of heat. For we shall find that a different ratio is given by each material forming the surface by which the heat is absorbed. The same difficulty is met with in a photographic plate. So that we have no means of determining the true distribution of radiant energy in the spectrum of any source of light, even if we should eliminate the errors due to absorption by the air, by the glass, or other material through which the beam has to pass, and the unequal dispersion in different portions of the spectrum.

In considering the subject of color or the sensation produced when waves of different lengths fall on the retina, we must recollect that this phenomenon is wholly subjective. Accordingly our knowledge of the aspect of these waves depends wholly on the construction of the eye. Young, in 1802, was the first to show that all the phenomena of color could be accounted for by supposing that the retina contained three kinds of nerves, each sensitive to waves of a certain length, that is, to a particular color. Other colors may be formed by exciting these nerves unequally. Thus a ray of yellow light will excite both the nerves sensitive to red and those sensitive to green, or will produce on the eye the same effect as if red and green rays are received together. In other words, red and green if mixed produce yellow, and not white, as is commonly supposed. The theory of Young was, however, quite forgotten until again brought forward in 1853, when the experiments of Helmholtz and Maxwell added greatly to their probability, and showed that the three

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primary colors, or colors to which the three kinds of nerves are sensitive, are red, green, and dark blue or violet. " In 1837, Sir David Brewster advanced the theory that there were three kinds of rays, physically unlike, which, on entering the eye, produced the sensations of red, yellow, and blue. According to this view, green would be formed by the combination of blue and yellow, while in reality they form white. No popular fallacy has attained a wider circulation than this, and even at the present time the erroneous view is largely maintained. The cause of this error is fully discussed in Chapter III"., and it is shown that it is in a great measure due to observations on the mixture of pigments, — a very fallacious method of combining colors.

If, now, we compare these two theories, we shall find them very different. According to Brewster, the cause of the difference of color is objective, that is, outside of the eye, and dependent on the nature of light. Although colors might affect the eyes of different persons or animals so as to produce different sensations in each, yet still every ray might be divided into the same three species, which would be present in all in the same proportion. Again, if in any way we could strike out a particular kind of ray, as red or yellow, the corresponding sensation, whatever it might be, would be wanting in all eyes. According to Young, on the other hand, the impression of color is wholly subjective or dependent on the formation of the particular eye by which it is viewed. As far as the light itself is concerned, the waves of different color are infinitely varied as regards their length, but, as the eye has only three tests for them by its three sets of nerves, our judgment is formed by the relative excitation of these three sets. In other words, according to Young, the three primary colors depend only on the eye, while, according to Brewster, they are inherent in the nature of light. Moreover, each nerve is sensitive, not only to rays of a particular color, but to all of nearly the same wave-length. Thus the red

INTRODUCTION.

xxm nerves are sensitive also to orange, though to a less degree, and even to yellow and green. It is impossible, therefore, to fix the exact hue of the three primary color sensations, but they should be regarded rather as representing certain portions of the spectrum. While, therefore, the simple phenomena of color are largely subjective, or dependent on the construction of the eye, the laws of contrast, either successive or simultaneous, depend wholly on the condition of the retina. They are, in fact, so many illusions to which the artist is subject, and by which he may be deceived unless he is acquainted with the laws governing them. The various relations of colors and how they should be combined are fully discussed in the last chapter of the book, beginning with the simplest two-color decorations, and ending with that highest application of color in art, the oil-painting.

Colors are sometimes divided by artists into primary, secondary, and tertiary, the first term being applied to the colors red, yellow, and blue of the spectrum. The other colors of the spectrum are called secondary or binary, since, according to Brewster's theory, each is composed of two primary colors, while tertiary colors are formed by combining two secondaries. These terms are not used in the present work, since they are based on the erroneous theory that the three elementary color sensations are inherent in the light, and not in the eye. In reality, all the colors of the spectrum are equally primary, being composed of rays of uniform wave-length, and all ordinary colors are formed of rays from every portion of the spectrum, differing only in the proportions in which they are combined.