Field's Chromatography Part 14

Cobalt, as furnis.h.i.+ng a blue colour, is usually a.s.sociated with alumina, silica, or tin; and, as furnis.h.i.+ng a green colour, with zinc. But there is obtainable a compound of zinc and cobalt which gives a blue not only free from green, but inclining rather to red. It is made by adding to a solution of ordinary phosphate of soda in excess a solution first of sulphate of zinc and then of sulphate of cobalt, and was.h.i.+ng and igniting the precipitate. The result is a vitreous blue with a purple cast, of little body, and exceedingly difficult to grind. Altogether, it is not unlike smalt, over which it has no advantages as an artistic pigment either in colour or permanence. For tinting porcelain, however, it is admirably adapted, imparting thereto a very pure dark blue of extraordinary beauty. This blue is distinguished from smalt by dissolving in acetic acid.

Compared with the wide range of yellows, or even with reds, the artist finds the number of his blues limited. The perfect native and excellent artificial ultramarines, the good blues of cobalt, the fair Prussian blue, and the doubtful indigo, are the four varieties he has for years been in the habit of using, and is still mainly dependent on. Our division, therefore, into permanent, semi-stable, and fugitive, is easily effected.

In the front rank, pre-eminent among blues as among pigments generally, stands genuine ultramarine. Behind it, are the artificial ultramarines; and behind them again, cobalt and cerulian blue. To a greater or less extent, all these are durable.

Among the semi-stable, must be cla.s.sed cyanine or Leitch's blue, smalt, and Prussian blue.

To the fugitive, belong indigo and the somewhat more permanent intense blue, Antwerp blue, and the copper blues.

In this list of blues, which grace or disgrace the palette of the present day, there is one colour which, although not permanent, is almost indispensable. As yet, the chemist cannot in all cases lay down the law as to what pigments may or may not be employed. The painter who unnecessarily uses fugitive colours must have little love for his craft, and a poor opinion of the value of his work; but, even with the best intentions and the utmost self-esteem, the artist cannot always confine himself to strictly stable pigments. He has no right to use orpiment instead of cadmium yellow, or red lead instead of vermilion, or copper blue instead of cobalt: he has no business to employ indigo when Prussian blue saddened by black will answer his purpose; but--what pigment can he subst.i.tute for Prussian blue itself? None. In its wondrous depth, richness, and transparency, it stands alone: there is no yellow to compare with it, no red to equal it, no blue to rival it. In force and power it is a colour among colours, and transparent beyond them all. The great importance of transparent pigments is to unite with solid or opaque colours of their own hues, giving tone and atmosphere generally, together with beauty and life; to convert primary into secondary, and secondary into tertiary colours, with brilliancy; to deepen and enrich dark colours and shadows, and to impart force and tone to black itself. For such effects, no pigment can vie with Prussian blue. What purples it produces, what greens it gives, what a matchless range of grays; what velvety glow it confers, how it softens the harshness of colours, and how it subdues their glare. No; until the advent of a perfect palette, the artist can scarcely part with his Prussian blue; nor can the chemist, who has nothing better to offer, hold him to blame. It is for Art to copy Nature with the best materials she possesses: it is for Science to learn the secrets of Nature, and turn them to the benefit of Art.

CHAPTER XI.

ON THE SECONDARY, ORANGE.

Orange is the first of the secondary colours in relation to light, being in all the variety of its hues composed of _yellow_ and _red_. A true or perfect orange is such a compound of red and yellow as will neutralize a perfect blue in equal quant.i.ty either of surface or intensity; and the proportions of such compound are five of perfect red to three of perfect yellow. When orange inclines to red, it takes the names of _scarlet_, _poppy_, &c.: in gold colour, &c., it leans towards yellow. Combined with green it forms the tertiary _citrine_, and with purple the tertiary _russet_: it also furnishes a series of warm semi-neutral colours with black, and harmonizes in contact and variety of tints with white.

Orange is an advancing colour in painting:--in nature it is effective at a great distance, acting powerfully on the eye, diminis.h.i.+ng its sensibility in accordance with the strength of the light in which it is viewed. It is of the hue, and partakes of the vividness of suns.h.i.+ne, as it likewise does of all the powers of its components, red and yellow.

Pre-eminently a _warm_ colour, being the equal contrast of or antagonist to blue, to which the attribute of _coolness_ peculiarly belongs, it is discordant when standing alone with yellow or with red, unresolved by their proper contrasts or harmonizing colours, purple and green. As an archeus or ruling colour, orange is one of the most agreeable keys in toning a picture, from the richness and warmth of its effects. If it predominate therein, for the colouring to be true, the violet and purple should be more or less red, the red more or less scarlet, the yellow more or less intense and orange, and the orange itself be intense and vivid. Further, the greens must lose some of their blue and consequently become yellower, the light blues be more or less light grey, and the deep indigo more or less marrone.

Although the secondary colours are capable of being obtained by admixture of the primaries in an infinitude of hues, tints, and shades; yet simple original pigments of whatever cla.s.s--whether secondary, tertiary, or semi-neutral--are, it has been said before, often superior to those compounded, both in a chemical and artistic sense. Hence a thoroughly good original orange is only of less value and importance than a thoroughly good original yellow, a green than a blue, or a purple than a red. To produce pure and permanent compound hues requires practice and knowledge, and we too often see in the works of painters combinations neither pleasing nor stable. Colours are a.s.sociated with each other which do not mix kindly, and compounds formed of which one or both const.i.tuents are fugitive. As a consequence, mixed tints are frequently wanting in clearness, and, where they do not disappear altogether, resolve themselves into some primary colour; orange becoming red by a fading of the yellow, green yellow by a fading of the blue, and purple blue by a fading of the red. Again, with regard to compound tints, there is the danger of one colour reacting upon and injuring another, as in the case of greens obtained from chrome yellow and Prussian blue, where the former ultimately destroys the latter. Of course a mixture of two permanent pigments which do not react on each other will remain permanent; the green, for instance, furnished by aureolin and native ultramarine lasting as long as the ground itself. To produce, however, the effects desired, the artist does not always stop to consider the fitness and stability of his colours in compounding, even if he possess the needed acquaintance with their physical and chemical properties. At all times, therefore, but especially when such knowledge is slight, good orange, &c., pigments are of more or less value, as by their use the employment of inferior mixtures is to a great extent avoided. In mingling primary with primary, if one colour does not compound well with the other, or is fugacious, the result is failure; but a secondary is not so easily affected by admixture: a green, for example, is seldom quite ruined by the injudicious addition of blue or yellow; and even if either of the latter be fugitive, the green will remain a green if originally durable. Thus the secondaries, if they are not already of the colour required, may be brightened or subdued, deepened or paled, with comparative impunity. The artist who, from long years of experience, knows exactly the properties and capabilities of the colours he employs, may in a measure dispense with secondary pigments, and obtain from the primaries mixed tints at once stable, beautiful, and pure; but even he must sometimes resort to them, as when a green like emerald or viridian is required, which no mixture of blue and yellow will afford. The primaries, by reason of their not being able to be composed of other colours, occupy the first place on the palette, and are of the first importance; but the secondaries are far too useful to be disregarded, and have a value of their own, which both veteran and tyro have cause to acknowledge.

The list of original orange pigments was once so deficient, that in some old treatises on the subject of colours, they are not even mentioned.

This may have arisen, not merely from their paucity, but from the unsettled signification of the term orange, as well as from improperly calling these pigments reds, yellows, &c. In these days, however, orange pigments are sufficiently numerous to merit a chapter to themselves; they indeed comprise some of the best colours on the palette.

155. BURNT SIENNA,

or _Burnt Terra di Sienna_, is calcined raw Sienna, of a rich transparent brown-orange or orange-russet colour, richer, deeper, and more transparent than the raw earth. It also works and dries better, has in other respects the qualities of its parent colour, and is a most permanent and serviceable pigment in painting generally. For the warm tints in rocks, mud banks, and buildings, this colour is excellent. When mixed with blue it makes a good green; furnis.h.i.+ng a bright green with cobalt, and one much more intense with Prussian blue. For the foresea, whether calm or broken by waves, it may be employed with a little madder; while compounded with a small portion of the latter and lamp black, it meets the hues of old posts, boats, and a variety of near objects, as the tints may be varied by modifying the proportions of the component colours. Used with white, it yields a range of sunny tones; and with aureolin or French blue and aureolin will be found of service, the last compound giving a fine olive green. Similar but fugitive greens are afforded by admixture of burnt Sienna with indigo and yellow or Roman ochre, or raw Sienna; tints which may be saddened into olive neutrals by the addition of sepia, and rendered more durable by subst.i.tuting for indigo Prussian blue and black. Mixed with viridian, it furnishes autumnal hues of the utmost richness, beauty, and permanence; and, alone, is valuable as a glaze over foliage and herbage. For the dark markings and divisions of stones a compound of Payne's gray and burnt Sienna will prove serviceable; while for red sails the Sienna, either by itself, with brown madder, or with Indian red, cannot be surpa.s.sed. For foregrounds, banks and roads, cattle and animals in general, burnt Sienna is equally eligible, both alone and compounded. It has a slight tendency to darken by time.

156. CADMIUM ORANGE

was first introduced to the art-world at the International Exhibition of 1862, where it was universally admired for its extreme brilliancy and beauty, a brilliancy equalled by few of the colours with which it was a.s.sociated, and a beauty devoid of coa.r.s.eness. We remember well the power it possessed of attracting the eye from a distance; and how, on near approach, it threw nearly all other pigments into the shade. It has in truth a l.u.s.trous luminosity not often to be met with, added to a total absence of rankness or harshness. A simple original colour, containing no base but cadmium, it is of perfect permanence, being uninjured by exposure to light, air or damp, by sulphuretted hydrogen, or by admixture. Having in common with cadmium sulphides a certain amount of transparency, it is invaluable for gorgeous sunsets and the like, either alone or compounded with aureolin. Of great depth and power in its full touches, the pale washes are marked by that clearness and delicacy which are so essential in painting skies. As day declines, and blue melts into green, green into orange, and orange into purple, the proper use of this pigment will produce effects both glowing and transparent. Transparency signifies the quality of being seen through or into; and in no better way can it be arrived at than by giving a number of thin washes of determined character, each lighter than the preceding one. With due care in preserving their forms, from the commencement to the termination, such washes of orange will furnish hues the softest and most aerial. For bits of bright drapery, a glaze over autumn leaves, and mural decoration, this colour is adapted; while in illumination it supplies a want formerly much felt. "With the exception of scarlet or bright orange," said Mr. Bradley, nine or ten years since, in his Manual of Illumination, "our colours are everything we could wish." As an original pigment, a permanent scarlet does not yet exist; but the brilliancy of cadmium orange cannot be disputed, nor its claim to be the only unexceptionable bright orange known. It even a.s.sists the formation of the other colour: remarks the author mentioned, "Brilliancy is obtained by gradation. Suppose a scarlet over-curling leaf, for example.

The whole should be painted in pure orange, with the gentlest possible after-touch of vermilion towards the corner under the curl. When dry, a firm line--not wash--of carmine, (of madder, preferable.--_Ed._), pa.s.sed within the outline on the shade side only of the leaf, will give to the whole the look of a bright scarlet surface, but with an indescribable superadded charm, that no merely flat colour can possess." In the same branch of art, illumination, cadmium orange, opposed to viridian, presents a most dazzling contrast, especially if relieved by purple.

157. CHINESE ORANGE

belongs to the coal-tar colours, and ought strictly to have been cla.s.sed therewith. We have preferred, however, to keep it separate, because, as Chinese Orange, it was introduced as a pigment, and has not been employed as a dye. In colour, it somewhat resembles burnt Sienna, enriched, reddened, brightened, and made more transparent, by admixture with crimson lake. From its behaviour, it would seem to be composed of yellow and red, such a compound as magenta and aniline yellow would afford. Its pale washes are uncertain, being apt to resolve themselves into red and yellow, of which the latter appears the most permanent; for, on exposure to light and air, the red more or less flies, leaving here a yellow, and there a reddish-yellow ground: in places both red and yellow disappear. Like all fugitive colours, it is comparatively stable when used in body; but even then it entirely loses its depth and richness, and in a great measure its redness, becoming faded and yellowish. In thin washes or glazing it is totally inadmissible; and, being neither a red, an orange, nor a brown, is unsuited to pure effects. Nevertheless, where it need not be unduly exposed; in portfolio illuminations, for instance, the richness, subdued brilliancy, and transparency of this pigment, justify its adoption. It is not affected by an impure atmosphere.

Aniline colours may be adapted for oil painting by dissolving them in the strongest alcohol, saturating the solution with Dammar resin, filtering the tincture, and pouring the filtrate either on pure water or solution of common salt, stirring well all the time. The water or brine solution must be at least twenty times the bulk of the tincture. The colour after being collected on a filter, washed, and dried, can be ground with linseed oil, poppy oil, or oil varnishes.

158. CHROME ORANGE,

_Orange Chrome_, or _Orange Chromate of Lead_, is a sub-chromate of lead of an orange-yellow colour, produced by the action of an alkali on chrome yellow. Like all the chromates of lead, it is characterized by power and brilliancy; but also by a rankness of tone, a want of permanence, and a tendency to injure organic pigments. By reason of its lead base it is subject to alteration by impure air, but is on the whole preferable to the chrome yellows, being liable in a somewhat less degree to their changes and affinities. As, however, a colour has no business to be used if a better can be procured, the recent introduction of cadmium orange renders all risk unnecessary.

159. MARS ORANGE,

_Orange de Mars_, is a subdued orange of the burnt Sienna cla.s.s, but without the brown tinge that distinguishes the latter. Marked by a special clearness and purity of tone, with much transparency, it affords bright sunny tints in its pale washes, and combines effectively with white. Being an artificial iron ochre it is more chemically active than native ochres, and needs to be cautiously employed with pigments affected by iron, such as the lakes of cochineal and intense blue.

160. MIXED ORANGE.

Orange being a compound colour, the place of original orange pigments can be supplied by mixtures of yellow and red; either by glazing one over the other, by stippling, or by other modes of breaking and intermixing them, according to the nature of the work and the effect required. For reasons lately given, mixed pigments are apt to be inferior to the simple or h.o.m.ogeneous both in colour, working, and other properties; yet some pigments mix and combine more cordially and with better results than others; as is the case with liquid rubiate and gamboge. Generally speaking, the compounding of colours is easier in oil than in water; but in both vehicles trouble will be saved by beginning with the predominating colour, and adding the other or others to it.

Perhaps in this, our first chapter on the secondary colours, and consequently on colours that can be compounded, a few remarks on mixed tints from a chemical point of view will not be deemed superfluous.

There are two ways, we take it, of looking at a picture--from a purely chemical, and from a purely artistic, point of view. Regarded in the first light, it matters little whether a painting be a work of genius or a daub, provided the pigments employed on it are good and properly compounded. The effects produced are lost sight of in a consideration of the materials, their permanence, fugacity, and conduct towards each other. Painting is essentially a chemical operation: with his pigments for reagents, the artist unwittingly performs reaction after reaction, not with the immediate results indeed of the chemist in his laboratory, but often as surely. As colour is added to colour, and mixture to mixture, acid meets alkali, metal animal, mineral vegetable, inorganic organic. With so close a union of opposite and opposing elements, the wonder is not so much that pictures sometimes perish, but that they ever live. It behoves the artist, then, not only to procure the best and most permanent pigments possible, but to compound them in such a manner that his mixed tints may be durable as well as beautiful. To effect or aid in effecting this, although he may not always be able to act upon them, the following axioms should be borne in mind:--

1. If they do not react on each other, a permanent pigment added to a permanent pigment yields a permanent mixture.

2. If they do react on each other, a permanent pigment added to a permanent pigment yields a semi-stable or fugitive mixture.

3. A permanent pigment added to a semi-stable pigment yields a semi-stable mixture.

4. A permanent pigment added to a fugitive pigment yields a fugitive mixture.

Consequently--

5. A permanent pigment may be rendered fugitive or semi-stable by improper compounding.

6. A semi-stable or fugitive pigment is not rendered durable by being compounded.

7. As a chain is only as strong as its weakest link, so a mixture is only as permanent as its least durable const.i.tuent.

To give ill.u.s.trations--

1. Ultramarine added to Chinese white yields a permanent mixture.

2. Ultramarine added to an acid constant white yields a semi-stable or fugitive mixture.

3. Ultramarine added to Prussian blue yields a semi-stable mixture.

4. Ultramarine added to indigo yields a fugitive mixture.

Except in the second instance, where the blue is either partially or wholly destroyed--in time, be it remembered, not at once--according to the quant.i.ty and strength of the acid in the white, the ultramarine remains unchanged. Hence at first sight our third and fourth conclusions may appear wrong; inasmuch as, it may be argued, a blue mixture cannot be semi-stable or fugitive when blue is left. To this we reply, unless both const.i.tuents are fugitive, a mixture will always more or less possess colour; but, if even one const.i.tuent be semi-stable or fugitive, a mixture will slowly but surely lose _the_ colour for which it was compounded, and be _as a mixture_ semi-stable or fugitive.

It need hardly be observed that the number of permanent orange, green, and purple hues which the artist can compound, depends mainly on the number of permanent yellows, reds, and blues at his disposal. In mixed orange, therefore, a selection of durable yellows and reds is of the first importance. It should, however, be remarked that mixed orange, more sober and less decided, is obtainable by the use of citrine and russet; in the former of which yellow predominates, and in the latter, red: consequently orange results when yellow is added to russet, red to citrine, or citrine to russet.

PERMANENT YELLOWS. | PERMANENT REDS.

| Aureolin. | Cadmium Red.

Cadmium, deep. | Liquid Rubiate.

Cadmium, pale. | Madder Carmine.

Lemon Yellow. | Rose Madder.

Mars Yellow. | Mars Red.

Naples Yellow, modern. | Ochres.