Field's Chromatography Part 25

is ivory charred to blackness by strong heat in closed vessels.

Differing chiefly through want of care or skill in preparing, when well made it is the richest and most transparent of all the blacks, a fine neutral colour perfectly durable and eligible both in water and oil.

When insufficiently burnt, however, it is brown, and dries badly; or if too much burnt, it becomes cineritious, opaque, and faint in hue. With a slight tendency to brown in its pale washes, this full, silky black is serviceable where the sooty density of lamp black would be out of place.

It is occasionally adulterated with bone black, a cheaper and inferior product.

Being nothing more nor less than animal charcoal, ivory or bone black had best not be compounded with organic pigments, in water at least. It is well known that this charcoal possesses the singular property of completely absorbing the colour of almost any vegetal or animal solution, and of rendering quite limpid and colourless the water charged with it. If a solution of indigo in concentrated sulphuric acid be diluted with water, and animal charcoal added in sufficient quant.i.ty, the solution will soon be deprived of colour. The more perfect the ivory or bone black, the more powerful is its action likely to be: either over or under calcined, animal charcoal is less energetic; in the former case, because it is less porous; in the latter, because the animal matter, not being wholly consumed, makes a kind of varnish in the charcoal which interferes with its acting. To a greater or less extent, gums, oils, and varnishes serve similarly as preventives, thereby decreasing the danger of employing these blacks in admixture; but, in the compounding of colours, nothing is gained by needless risk. To mix with organic pigments, therefore, blue or lamp blacks should be subst.i.tuted for those of ivory or bone; that is, vegetal charcoal should be used instead of animal. It is a question whether even with inorganic pigments the adoption of the former in admixture would not be advisable.

It was once the general opinion that the action of animal charcoal was limited to bodies of organic origin, but it has since been found that inorganic matters are likewise influenced. "Through its agency," says Graham, "even the iodine is separated from iodide of pota.s.sium;" whence probably pigments containing iodine would suffer by contact. The investigation of Weppen appears to prove that the action of the charcoal extends to all metallic salts; with the following, no doubt remains of this being so, to wit:--the sulphates of copper, zinc, chromium, and protoxide of iron; the nitrates of lead, nickel, silver, cobalt, suboxide and oxide of mercury; the protochlorides of tin and mercury; the acetates of lead and sesquioxide of iron; and the tartrate of antimony. Whether animal charcoal exercises any deleterious influence on pigments consisting of these metals, and, if so, how far and under what circ.u.mstances, can only be answered when our knowledge of the properties of pigments is greater than it now is. At present, perhaps, it is safer to choose vegetal charcoal for mixed tints, inasmuch as, although it shares the property of bleaching in a certain degree, it does not possess the same energy.

294. LAMP BLACK,

or _Lamblack_, is a smoke black, being the soot procured by the burning of resins or resinous woods. It is a pure vegetal charcoal of fine texture, not quite so intense nor so transparent as the black made from ivory, but less brown in its pale tones. It has a very strong body that covers readily every underlay of colour, works well, but dries badly in oil. On emergency, it may be prepared extemporaneously for water-painting by holding a plate over the flame of a lamp or candle, and adding gum to the colour: the nearer the plate is held to the wick of the lamp, the more abundant and warm will be the hue of the black obtained; at a greater distance it will be more effectually charred, and blacker.

Mixed with French blue or cobalt, lamp black gives good cloudy grays, which are useful for the shadows of heavy storm clouds. With French blue and this black alone various beautiful stormy skies may be represented; the contrast of the blue causing the black to a.s.sume, if desired, a warm tone in shadows. For like purposes, the black with ultramarine ash affords a very soft hue, and with light red and cobalt in different proportions yields silvery tones most serviceable. To the dark marking of murky and dirty clouds, a compound of lamp black and light red is particularly suited; while a mixture of the black with cobalt and purple madder is adapted for slate-coloured sunset and sunrise clouds. French blue softened with a little lamp black is fitted for mountains or hills, very remote; and the same blue and black with rose madder meet their tints if nearer. In seas the black is useful with raw Sienna and other colours; while, whether in storm or calm, vessels and boats may be painted with tints of lamp black, madder brown, and burnt Sienna, varying in degrees of strength according to the distances. Lamp black alone, or with French blue, cobalt and purple madder, emerald green, or rose madder, is good for rocks; and for dark foreground objects when mixed with madder lake and burnt Sienna. With aureolin the black furnishes a sober olive for foliage, and with rose madder a fine colour for the stems and branches of trees. Compounded with light red, it is suited to the first general tones of the ground for banks and roads; and with yellow ochre or madder red, to parts of buildings and cattle. A very eminent miniature painter recommends for hair tints, lamp black, Indian red, and burnt Sienna. Being a dense solid colour, this black must be used sparingly to avoid heaviness.

Hitherto confined to painting and engraving, lamp black has lately refuted the a.s.sertion that there is nothing new under the sun by making its appearance in photography. By a method which combines the fidelity of that art with the permanence of prints, there is produced a species of photographic engraving, so to speak, having lamp black or carbon for its colouring matter. Indeed, in this 'Autotype' process, as it is called, any other durable pigment or pigments may be used, and a photographic picture thus obtained. In copying the works of artists, especially, the mode promises to be of value, inasmuch as by its agency the same pigments may be made the colouring matter of the reproduction as are employed in the original. If this be in sepia or bistre, the copy can be autotyped in those colours; or if a red chalk drawing be required to be multiplied, the proofs may be in red chalk, the copy when produced to the same scale being scarcely distinguishable from the original. In like manner, any single colour of the artist's palette is applicable without restriction or limitation, so that not only are every line and touch rendered absolutely, but the very pigment used in the original is found in the copy. Moreover, as the pigments are quite unchanged by the action of the other agents employed, the resulting colour of the print is determined once for all, just as the artist mixes those pigments on his palette for his picture. As extending the use of lamp black and permanent pigments in general, this brief digression on Autotypography may be pardoned in a treatise on colours.

295. MIXED BLACK.

Black is to be considered as a synthesis of the three primary colours, the three secondaries, or the three tertiaries, or of all these together; and, consequently, also of the three semi-neutrals, and may thus be composed of due proportions of either tribe or triad. All antagonistic colours, or contrasts, likewise afford the neutral black by composition; but in all the modes of producing black by compounding colours, blue is to be regarded as its archeus or predominating colour, and yellow as subordinate to red, in the proportions, when their hues are true, of eight blue, five red, and three yellow. It is owing to this predominance of blue in the const.i.tution of black, that it contributes by mixture to the pureness of hue in white colours, which usually incline to warmth, and that it produces the cool effect of blueness in glazing and tints, or however otherwise diluted or dilated.

It accords with the principle here inculcated that in gla.s.s-founding the oxide of manganese, which gives the _red_ hue, and that of cobalt, which furnishes the _blue_, are added to brown or _yellow_ frit, to obtain a velvety black gla.s.s. Similarly the dyer proceeds to dye black upon a deep blue basis of indigo, with the ruddy colour of madder and the yellow of quercitron, &c.

Some of the best blacks and neutrals of the painter are those formed with colours of sufficient power and transparency upon the palette.

Prussian blue and burnt lake afford a powerful though not very durable black; and compound blacks in which transparent pigments are employed will generally go deeper and harmonize better with other colours than any original black pigment alone. Hence lakes and deep blues, added to the common blacks, greatly increase their clearness and intensity: in mixture and glazing of the fine blacks of some old pictures, ultramarine has evidently been used. In this view, black altogether compounded of blue with red and yellow, each deep and transparent, and duly subordinated according to its powers, will give the most powerful and transparent blacks; although, like most other blacks, they dry badly in oil. Of course, as with all compound colours, it depends entirely on the pigments employed whether these mixed blacks are permanent or not: a compound black can very well pa.s.s through the stages of black to grey, gray, or dirty white, if each link in the chain of combination be not as strong as its fellows.

296. _Black Chalk_

is an indurated clay, of the texture of white chalk, and chiefly used for cutting into crayons. Fine specimens have been found near Bantry in Ireland, and in Wales, but the Italian has the most reputation. Crayons for sketching and drawing are also artificially prepared, which are deeper in colour and free from grit. Wood charcoal is likewise cut into crayons, that of soft woods, such as lime, poplar, &c., being best adapted for the purpose.

297. _Black Ochre_,

Earth Black, or Prussian Black, is a native earth, combined with iron and alluvial clay. It is found in most countries, and should be washed and exposed to the atmosphere before being employed. Sea-coal, and other black mineral substances, have been and may be used as subst.i.tutes for the more perfect blacks, when the latter are not procurable, which now seldom or never happens.

298. _Bone Black_,

obtained by charring, is similar to that of ivory, except that it is a little warmer in tone, having a reddish or orange tinge, and is a worse drier in oil. Like ivory black, it is very transparent. Immense quant.i.ties of bone black are consumed with sulphuric acid in the manufacture of shoe blacking.

299. _Coffee Black_,

though little known and not on sale, has been strongly recommended by Bouvier as one of the best blacks that can be used. Soft without being greasy, light, almost impalpable, even before being ground, it gives tints of a very bluish gray when mixed with white, a quality precious for making the blues of the sketch, and dull greens. It is said to dry better than blue or vine black, and to combine admirably with other colours. De Montabert prefers calling it Coffee Brown, giving it as an exemplification of a bluish-brown, but probably this brown hue is owing to want of skill in its manufacture. We have not had personal experience of the colour, but there is no theoretical reason why a carbonaceous black should not be produced from coffee. The mode of proceeding is to calcine the berry in a covered vessel, and well wash the resulting charcoal with boiling water by decantation. In order to prevent the powder, which is of great lightness, from floating, it is made into paste with a few drops of alcohol before adding the water.

300. _Frankfort Black_

is said to be made of the lees of wine from which the tartar has been washed, by burning, in the manner of ivory black; although the inferior sort is merely the levigated charcoal of woods, of which the hardest, such as box and ebony, yield the best. Fine Frankfort black, though almost confined to copper-plate printing, is one of the best black pigments extant, being of a neutral colour, next in intensity to lamp black, and more powerful than that of ivory. Strong light has the effect of deepening its colour. It is probable that this was the black used by some of the Flemish painters, and that the pureness of the greys formed therewith is due to the property of charred substances of preventing discolourment.

301. _Manganese Black_,

the common black oxide of that metal, is the best of all blacks for drying in oil without addition. It is also a colour of vast body and tingeing power. As a siccative, it might be advantageously employed with ivory black.

302. _Mineral Black_

is a native impure carbon of soft texture, found in Devons.h.i.+re. Blacker than plumbago, and free from its metallic l.u.s.tre, it is of a neutral colour, greyer and more opaque than ivory black, and forms pure neutral tints. Being perfectly durable, and drying well in oil, it is of value in dead colouring on account of its solid body, as a preparation for black and deep colours before glazing. It would likewise be the most permanent and best possible black for frescoes.

303. _Paper Black_,

a pigment unknown to the modern palette, like most of our numbered italicised colours, is of the nature of blue or vine black. Very soft and of a fine bluish-gray, it is fitted for flesh, or for mixing with whites or yellows in landscapes.

304. _Peach Black_,

or Almond Black, made by burning the stones of fruits, the sh.e.l.l of the cocoa-nut, &c., is a violet-black, once much used by Parisian artists.

Bouvier believes it to be a good black, but at the same time sensibly asks, of what use is it to have a black of this cast, which can always be given by lake, without diminis.h.i.+ng but rather increasing the intensity of the black it may be mixed with.

305. _Prussian Black._

The same Prussian blue which gives a brown when burnt in the open air, yields a black when calcined in a close crucible. Very intense, very soft and velvety, and very agreeable to work, this bluish-black dries much more promptly than most other blacks, and scarcely requires grinding. On account of its extreme division, however, it would probably be found more energetic as a decolourising agent in admixture with organic pigments than most carbonaceous blacks.

Another Prussian black, containing copper, and made by a wet process, is obtained when a dilute solution of cupric sulphate and ferrous sulphate, in proper proportions, is mixed with a quant.i.ty of ferrocyanide of pota.s.sium not in excess. A very bulky deep black precipitate is formed, which is difficult to wash, and is deep black when dry. It is insoluble in water, and appears to be a compound a.n.a.logous to Prussian blue. As a pigment, this black is inferior to the preceding.

306. _Purple Black_

is, or rather was, a preparation of madder, of a deep purple hue approaching black. Powerful and very transparent, it glazed and dried well in oil, and was a durable and eligible pigment. Its tints with white lead were of a purple cast.

307. _Spanish Black_,

or Cork Black, is a soft black, obtained by charring cork, and differs not essentially from Frankfort black, except in being of a lighter and softer texture. "Some of my friends," says Bouvier, "call it _Beggars'

Ultramarine_, because it produces, by combinations, tints almost as fine as ultramarine." A blue but not a velvet black, where intensity is required some other is to be preferred. For mixtures, however, it is stated to be admirable, and especially for linen, skies, distances, and the various broken tints of carnations, &c.

Besides those blacks which have been mentioned, there are others furnished by several of the metals and by many organic substances employed as dyes; but as the blacks in common use are all permanent, and have been found sufficient for every purpose, it is scarce needful to swell the list. Nor is it more needful, the Editor considers, to swell the book; lest his aim be defeated of reflecting in a _moderate_-sized mirror the palette as it is and might be at the present day. Arrived at age, as it were, in its twenty-first chapter, this treatise may fitly conclude with Black, the last of the series of colours. Let us hope the maxim of Sir Joshua Reynolds, that success in some degree was never denied to earnest work may apply here.

Still, by way of finale, we would offer a few remarks. In no branch of the science, perhaps, is it more hazardous to commit oneself to a positive dictum than in the chemistry of colours, so liable are theory and practice to clash, and so often does the experience of one person or one time differ from that of another. He who has turned his attention to pigments, finds nearly every a.s.sertion must be qualified, for to nearly every rule there is some exception, and learns that theory alone may mislead. For example, a colour known to be fugacious may last, in certain cases, a surprisingly long time; while, on the contrary, a pigment permanent when used alone, may be rendered fugitive by improper compounding. Again, what holds good of a colour produced by one process, or employed in one vehicle or by one artist, may not be true of the same colour made by a different mode, or used in another vehicle or by another artist. It is because, then, colours are of every degree of durability, from the perfectly stable to the utterly fugitive, and because each one is liable to influence by every condition of time, place, and circ.u.mstance, that the chemist's theory is opposed as often to the painter's practice as the experience of artists themselves varies. This may explain the charges of inconsistency and contradiction which have been brought against writers on pigments, faults that lie rather with the nature of the subject than with the authors.

Even at the risk of being tiresome, we have throughout insisted on the choice of permanent pigments, not simply for use alone but for mixed tints. To quote Cennini, "I give you this advice, that you endeavour always to use ... good colours.... And if you say that a poor person cannot afford the expense, I answer, that if you work well (and give sufficient time to your works), and paint with good colours, you will acquire so much fame that from a poor person you will become a rich one; and your name will stand so high for using good colours, that if some masters receive a ducat for painting one figure, you will certainly be offered two, and your wishes will be fulfilled, according to the old proverb, 'good work, good pay.'" Of a truth, if man cannot dip his brush in the rainbow and paint with the aerial colours of the skies, he can at least select the best pigments that earth and the sea afford him; preferring, where he cannot get brilliancy and permanence combined, sobriety and permanence to brilliancy and fugacity. It must be the wish of every real artist to leave behind him a lasting record of his skill, a permanent panorama of those hues of nature which in life he loved so well. To effect this, genius alone is powerless: there must be first a proper choice of materials, and next a proper use of them. The painter's pigments are the bricks wherewith the mortar of his mind must be mixed, either to erect an edifice that shall endure for ages, or one which will quickly topple over like a house of cards. Now in nothing more than in painting is prevention better than cure--indeed cure may be said to be here out of the question: for good or for evil a picture once painted is painted for ever. Without a strong const.i.tution there is no hope for it; no chemistry can strengthen the sickly frame, restore the faded colour, stop the ravages of consumption: Science stands helpless before dying Art.

And yet, she sighs to think, it might have been otherwise. If durable pigments had been employed, if her counsel had been sought, this need not have been. In the history of modern art the use and abuse of colours would furnish a sad chapter, telling of gross ignorance, and a grosser indifference. Happily there is promise of a healthier state of things.

When this comes, Art will be less shy to consult her sister: in the interests of both there should be closer union. Without waiting till the picture is finished--for then it will be too late--let her, if in doubt, frankly display the contents of her palette and ask advice. Now, not knowing what pigments are chosen or how they are used, never standing by and watching the progress of the work, how can Science lend her aid?

She would willingly, for she herself needs help: at present her knowledge is limited, not so much of the chemistry of colours as of the properties of pigments. She seeks to mix her pound of theory with an ounce of practice, and craves a warmer welcome to the studio. For any approximation to the truth to be arrived at, facts must be noted with the conditions under which they occur, not by one sister alone nor by the other alone, but by both. In future, Art and Science should go hand in hand, mutually dependent on each other, mutually trustful of each other, working with and for each other, earnestly and patiently.

FOOTNOTES:

[C] Light is either direct or diffused--direct, when the sun's rays fall upon any object; diffused, when ordinary daylight illumines objects with white light, causing them to appear of their peculiar colours.

ADDENDUM.

With the present rapid progress of applied chemistry, an addendum in a work of this kind is quite excusable. Even while the book is being printed some fact may be announced which the author or editor would wish to insert. In our case this has happened. Very recently there has been introduced in France as a pigment