Field's Chromatography Part 18

Verdigris, chrome greens, and sap green, should be branded as fugitive: the chrome greens, because they are always commercially composed of chromate of lead and Prussian blue, two compounds which are semi-stable in themselves, but become fugacious when compounded.

A reference to the numbered italicised greens will show that there are many not known to the palette, which are nevertheless very greatly superior, as regards permanence, to some that disgrace it. Why these latter are suffered to hold their position is a mystery not easily explained: it is hard to reconcile the deplored degeneracy of modern pigments with the popularity of semi-stable and fugitive colours.

Pictures do not stand, is the common cry; therefore, says the public, there are no good pigments now-a-days. To which we answer, newly built houses are constantly falling down; therefore there are no good bricks in these times. Of a truth, one conclusion is as reasonable as the other: in either case, if rotten materials be used, the result cannot be lasting; but in neither case does it follow, because such materials are employed, that there are no better obtainable. A well-built house implies a conscientious builder, and a well-painted picture implies a conscientious artist. It is because, we fear, that there are so few conscientious artists, that there are so few permanent paintings; not, certainly, because there are no good pigments. In this last belief, however, the public is encouraged by certain painters, who seek thereby to excuse their own shortcomings, forgetting that it is a bad workman who finds fault with his tools. It has been well observed that when artists speak regrettingly of lost 'systems,' or pigments enjoyed by the mediaevalists and unattainable now, it would be far better were they to make the best use of existing materials, and study their further development. There is no need for this cant cry of fugacity, which casts such a blight on modern art. Durable pigments are not yet obsolete, they have only to be employed and employed properly to furnish paintings equal in permanence to those of the old masters. "t.i.tian," says Haydon, "got his colours from the colour shops on the Rialto, as we get ours from Brown's; and if Apelles or t.i.tian were living now, they would paint just as good works with our brushes and colours as with their own."

CHAPTER XIII.

ON THE SECONDARY, PURPLE.

Purple, the third and last of the secondary colours, is composed of _red_ and _blue_, in the proportions of five of the former to eight of the latter; proportions which const.i.tute a perfect purple, or one of such a hue as will neutralize and best contrast a perfect yellow, in the ratio of thirteen to three, either of surface or intensity. When mixed with its co-secondary colour, green, purple forms the tertiary _olive_; and, when compounded with the remaining secondary, orange, it const.i.tutes in like manner the tertiary _russet_. Of the three secondary colours it is the coolest, as well as the nearest in relation to _black_ or shade; in which respect, and in never being a warm colour, it resembles blue. In other respects also, purple partakes of the properties of blue, which is its archeus, or ruling colour; hence it is to the eye a retiring colour, that reflects light little, and loses rapidly in power in a declining light, and according to the distance at which it is viewed. By reason of its being the mean between black and blue it becomes the most retiring of all positive colours. Nature employs this hue beautifully in landscape, as a sub-dominant, in harmonizing the broad shadows of a bright sunshine ere the light sinks into deep orange or red. Girtin, who saw Nature as she is, and painted what he saw, delighted in this effect of sunlight and shadow. As a ruling colour, whether in flesh or otherwise, purple is commonly too cold, or verges on ghastliness, a fault which is to be as much avoided as the opposite extreme of viciousness in colouring, stigmatized as foxiness.

Yet, next to green, purple is the most generally pleasing of the consonant colours; and has been celebrated as a regal or imperial colour, as much perhaps from its rarity in a pure state, as from its individual beauty. Romulus wore it in his trabea or royal mantle, and Tullus Hostilius, after having subdued the Tuscans, a.s.sumed the pretexta or long robe, broadly striped with purple. Under the Roman emperors, it became the peculiar emblem or symbol of majesty, and the wearing of it by any who were not of the Imperial family, was deemed a "treasonable usurpation," punishable by death. At the decline of the empire, the Tyrian purple was an important article of commerce, and got to be common in the clothing of the people. Pliny says, "Nepos Cornelius, who died in the reign of Augustus Caesar, when I was a young man, a.s.sured me that the light violet purple had been formerly in great request, and that a pound of it usually fetched 100 denaria (about 4 sterling): that soon after the tarentine or reddish purple came into fashion; and that this was followed by the Tyrian dibapha, which could not be bought for less than 1000 denaria (nearly 40 sterling) the pound; which was its price when P. Lentulus Spinter was aedile, Cicero being then Consul. But afterwards, the double-dyed purple became less rare, &c." The Tyrian purple alluded to was obtained from the purpurae, a species of sh.e.l.l-fish adhering to rocks and large stones in the sea adjoining Tyre. On account, probably, of its extreme costliness, it was frequently the custom to dye the cloth with a ground of kermes or alkanet, previous to applying the Tyrian purple. This imparted to the latter a crimson hue, and explains doubtless the term, double-dyed. The Greeks feigned the ancient purple to be the discovery of Hercules Tyrius, whose dog, eating by chance of the fish from which it was produced, returned to him with his mouth tinged with the dye. Alexander the Great is said to have found in the royal treasury, at the taking of Susa, purple to the enormous value of 5000 talents,[A] which had lain there one hundred and ninety-two years, and still preserved its freshness and beauty.

When inclining to red, purple takes the name of _crimson_, &c.; and when leaning to blue, the names of _violet_, _lilac_, _mauve_, _&c._ Blue is a colour which it serves to mellow, or follows well into shade. The contrast or harmonizing colour of purple is yellow on the side of light and the primaries; while purple itself is the harmonizing contrast of the tertiary _citrine_ on the side of shade, and less perfectly so of the semi-neutral _brown_. As the extreme primaries, blue and yellow, when either compounded or opposed, afford, though not the most perfect harmony, yet the most pleasing consonance of the primary colours; so the extremes, purple and orange, yield the most pleasing of the secondary consonances. This a.n.a.logy extends likewise to the extreme tertiary and semi-neutral colours, while the mean or middle colours furnish the most agreeable contrasts or harmonies.

In nature pure purple is not a common colour, and on the palette purple pigments are singularly few. They lie under a peculiar disadvantage as to apparent durability and beauty of colour, owing to the neutralizing power of yellowness in the grounds upon which they are laid; as well as to the general warm colour of light, and the yellow tendency of almost all vehicles and varnishes, by which the colour of purple is subdued.

208. BURNT CARMINE

is the carmine of cochineal partially charred till it resembles in colour the purple of gold, for which, in miniature and water-painting, it is subst.i.tuted. It is a magnificent reddish purple of extreme richness and depth, eligible in flower-painting and the shadow of draperies. As it is generally impossible, however, to alter the nature of a pigment by merely changing its colour, burnt carmine is scarcely more permanent than the carmine from which it is produced. If used, therefore, it should be in body, and not in thin washes or as a glaze.

Durable pigments are admissible in any form; but semi-stable pigments (gamboge excepted) should only be employed in body.

209. BURNT LAKE

holds the same relation to crimson lake as burnt carmine to ordinary carmine; and is hence a weaker variety of the preceding, with less richness, and likewise less permanence.

210. INDIAN PURPLE

is prepared by precipitating an extract of cochineal with sulphate of copper. It is a very deep-toned but rather cold and subdued purple, neither so red nor so brilliant as burnt carmine; and is chiefly of service in draperies. It is apt to lose its purple colour in a great measure on exposure to light and air, and a.s.sume an inky blackness; a defect which becomes less apparent when the pigment is used in bulk.

211. MARS VIOLET,

_Violet de Mars_, _Purple Ochre_, or _Mineral Purple_, is a dark ochre, native of the Forest of Dean in Gloucestershire. It is of a murrey or chocolate colour, and forms cool tints of a purple hue with white. It is of a darker colour than Indian red, which has also been cla.s.sed among purples, but has a similar body and opacity, and generally resembles that pigment. It may be prepared artificially, and some natural red ochres burn to this colour. Being difficult and sometimes impossible to procure, Mars violet is often compounded; in which case it is liable to vary both in hue and stability. As, however, Indian red is always taken for its basis, the mixture is never wholly fugitive, nor exhibits any very glaring contrast on exposure.

212. MIXED PURPLE.

Purple being a secondary colour, composed of _blue_ and _red_, it follows of course that any blue and red pigments, which are not chemically at variance, may be employed in producing mixed purples of any required hue, either by compounding or grinding them together ready for use, or by combining them in the various modes of operation in painting. In such compounding, the more perfect and permanent the original colours are, the more perfect and permanent will be the purple obtained. To produce a pure purple, neither the red nor the blue must contain or incline to yellow; while to compound a durable purple, both the red and the blue must be durable also. Ultramarine and the reds of madder yield beautiful and excellent purples, equally stable in water or oil, in glazing or tint, whether under the influence of light or impure air. Cobalt blue and madder red likewise afford good purples; and some of the finest and most delicate purples in ancient paintings appear to have been composed of ultramarine and vermilion, which furnish tints equally permanent, but less transparent than the above, and less easily compounded. Facility of use, and other advantages, are obtained at too great a sacrifice by the employment of perishable mixtures, such as the lakes of cochineal with indigo.

PERMANENT REDS. | PERMANENT BLUES.

| Cadmium Red. | Cerulian Blue.

Liquid Rubiate. | Cobalt Blue.

Madder Carmine. | Genuine Ultramarine.

Rose Madder. | Brilliant Ultramarine.

Mars Red. | French Ultramarine.

Ochres. | New Blue.

Vermilions. | Permanent Blue.

It should be noted that all the above reds do not afford pure purples with blue; those which contain more or less yellow, as cadmium red and orange vermilion, furnish purples partaking more or less of olive, which is a compound of purple and green. To those reds may be added the russet Rubens Madder and the marrone Madder Brown, two pigments which are alike eligible for mixed purple and mixed orange. No purple, it will be remarked, equal in gorgeous richness to that produced from crimson lake and Prussian blue is obtainable from the colours given; just as no mixed green is of such depth and power if that blue be wanting as a const.i.tuent. But, as our compound tints are given rather as examples of durability than beauty, all semi-stable or fugitive mixtures are of necessity ignored.

213. PURPLE MADDER,

_Field's Purple_, or _Purple Rubiate_, is the only durable organic purple the palette possesses. Marked by a soft subdued richness rather than by brilliancy, it leans somewhat towards marrone, and affords the greatest depth of shadow without coldness of tint. Unfortunately, in the whole range of artistic pigments there is no colour obtainable in such small quant.i.ty as madder purple; hence its scarcity and high price cause it to be confined to water-colour painting, in which the clearness and beauty of its delicate tones render it invaluable in every stage of a drawing. With raw Sienna and indigo or Prussian blue, subdued by black, it gives beautiful shadow tints, and will be found useful in sky and other effects compounded with cobalt, rose madder, French blue and sepia, yellow ochre and cobalt, lamp black and cobalt, light red, Vand.y.k.e brown, burnt Sienna, or aureolin. With great transparency, body, and depth, it is pure and permanent in its tints, neither gives nor sustains injury on admixture, dries and glazes well in oil, works well, and is altogether most perfect and eligible. For fresco it is admirably adapted, being quite uninjured by lime.

There is a lighter and slightly brighter sort, containing less colouring matter and more base, which has all the properties of the above with less intensity of colour. For the sake of cheapness, the purple is sometimes compounded in oil, generally of brown madder and a blue.

Provided the latter be stable, transparent, and mix kindly, no greater objection can be taken to this than to the neutral orange of brown madder and yellow ochre.

214. VIOLET CARMINE

is a brilliant bluish purple of much richness, employed in draperies and the like. It is prepared by precipitating an alcoholic extract of the root of the _Anchusa tinctoria_, commonly known as alkanet, a plant growing in the Levant, and some other warm countries. It was used by the ancients as a dye, or as a groundwork to those stuffs which were to be dyed purplish-red: the ladies in ancient times also employed it as a paint. Its colouring matter or _anchusin_ has the character of a resin, and is dark-red, softened by heat, insoluble in water, soluble in alcohol and alkalis, and freely so in ether, fats, and volatile oils, to all of which it imparts a brilliant red hue. To obtain anchusin, all the soluble matters are first abstracted from the bruised root by water: it is then digested in a solution of carbonate of potash, from which it may be readily precipitated by an acid. Its alcoholic solution yields with different reagents crimson, flesh-coloured, blue, and violet precipitates, none of which, however, can be cla.s.sed as durable. The variety under notice, violet carmine, resembles the other colours afforded by alkanet in not being able to withstand the action of light.

On continued exposure, it loses its beauty and brightness, together with much of its colour, and, like Indian purple, a.s.sumes an inky blackness.

Hence it is unsuited to permanently pure effects, and should only be used in body.

215. _Archil Purple._

Archil may be regarded as the English, cudbear as the Scotch, and litmus as the Dutch name for one and the same substance, extracted from several species of lichens by various processes. These lichens, which are princ.i.p.ally collected on rocks adjacent to the sea, are cleaned and ground into a pulp with water, treated from time to time with ammoniacal liquor, and exposed with frequent agitation to the action of the atmosphere. Peculiar principles existing in the lichens are, by the joint instrumentality of the air, water, and ammonia, so changed as to generate colouring matter, which, when perfect, is expressed. Soluble in water and alcohol, this colouring principle yields by precipitation with chloride of calcium a compound known as 'Solid French Purple', a pigment more stable than the archil colours generally, but all too fugitive for the palette.

216. _Bis.m.u.th Purple._

A purple powder is capable of being produced from bis.m.u.th by pa.s.sing chlorine gas through the hydrated oxide suspended in a saturated solution of potash. As soon as the oxide becomes brown-red, the mixture is boiled and the liquid decanted off at once, the residue being immediately washed first with alcohol and then with water. On the whole, the result is not, for an artistic pigment, worth the trouble involved in the preparation.

217. _Burnt Madder_

is obtained by carefully charring madder carmine until it becomes of the hue required. Bearing the same relation to madder carmine as burnt carmine to the carmine of cochineal, burnt madder is a permanent and perfectly unexceptionable pigment. By reason, probably, of its great price, it is not mentioned in trade catalogues, and must be held as commercially unknown.

218. _Cobalt Purples_

are obtainable ranging from the richest crimson purple to the most delicate violet. We have produced them by wet and dry methods, varying in brilliancy and beauty, but characterised generally by want of body, and frequently by a smalt-like grittiness. Chemically, good and stable colours, they are not received with favour on the palette, and certainly may be very well replaced by mixtures of cobalt blue and madder red.

When a permanent compound is obtainable equal in colour to an original pigment, and superior in its physical attributes, no objection can fairly be taken to its artistic preference. There are other things to be considered in a pigment besides permanence, or even permanence and colour combined. The two together do not const.i.tute a perfect pigment, that is, a material of practical utility and value. In the last chapter, allusion was made to a green which possesses both the one and the other, and yet is--at present, at least--quite unfitted for artistic use. Hence, with a strong partiality for simple original pigments, we are bound to confess there are cases where mixtures are justifiably preferred. All we contend for is, that each const.i.tuent of such mixtures should be stable, and neither give nor receive injury by being compounded.

219. _Gold Purple_,

Purple of Ca.s.sius, or Ca.s.sius's Purple Precipitate, was discovered in 1683 by Ca.s.sius of Leyden. It is a compound of tin and gold, best formed by mixing aqueous perchloride of iron with aqueous protochloride of tin, till the colour of the liquid has a shade of green, and then adding this liquid, drop by drop, to a solution of perchloride of gold, which is free from nitric acid and very dilute: after twenty-four hours the purple is deposited. When recently prepared, the colour is brightened by boiling nitric acid. Not brilliant, but rich and powerful, this purple varies in hue according to the mode of manufacture from deep crimson to murrey or dark purple: it also differs in degrees of transparency.

Working well in water, it is an excellent though costly pigment, once popular in miniatures, but at present rarely, if ever used, as purple madder is cheaper, and perfectly well supplies its place. Retaining its colour at a high red heat, it is now confined to enamel and porcelain painting, and to tinging gla.s.s of a fine red. If, whilst in its hydrated state, it be washed with ammonia, a bright purple liquid results, from which a violet colour, somewhat less expensive, can be produced, by combining the gold purple with alumina, and calcining the product in the same way that is practised with cobalt. This compound may be exposed to the action of the sun's rays for a year without being sensibly affected.

220. _Prussian Purple._

A prussiate of iron is obtainable of a violet hue, affording good shadow tints and clear pale washes. It has not, however, been introduced as a pigment, as ordinary Prussian blue tinged with red furnishes a similar colour.

221. _Sandal Wood Purple._

Sandal wood contains about 16 per cent. of colouring matter, soluble with difficultly in water, but readily dissolved by alcohol. From the latter solution, chloride of tin throws down a purple, and sulphate of iron a deep violet precipitate; neither of which is remarkable for permanence.

222. _Tin Violet._