Field's Chromatography Part 22

253. MUMMY,

_Mummy Brown_, or _Egyptian Brown_, is a bituminous product mixed with animal remains, brought from the catacombs of Egypt, where liquid bitumen was employed three thousand years ago in embalming. By a slow chemical change, it has combined during so many ages with substances which give it, as a rule, a more solid and lasting texture than simple asphaltum. Generally resembling the latter in its other properties and uses as a pigment, mummy is often subst.i.tuted for it, being less liable to crack or move on the canva.s.s. It must be remembered, however, that mummy varies exceedingly both in its composition and qualities; and as from its very nature and origin nothing certain can be said of it, but little reliance should be placed on this brown. Mummy belongs to the cla.s.s of pigments which are either good or bad, according as they turn out. On the whole, we agree with the American artist, who has been more than once quoted in these pages, that nothing is to be gained by smearing one's canva.s.s with a part, perhaps, of the wife of Potiphar.

With a preference for materials less frail and of a more sober character, we likewise hold with Bouvier, that it is not particularly prudent to employ without necessity these crumbled remains of dead bodies, which must contain ammonia and particles of fat in a concrete state and so be more or less apt to injure the colours with which they may be united. The use of mummy is now confined to oil, in which, says Mr. Carmichael, a mixture of mummy and bitumen will dry and never crack.

If this be the case, the compound would be preferable to either separate.

254. PRUSSIAN BROWN

is an iron oxide, containing more or less alumina, and prepared by calcining an aluminous Prussian blue, or treating an aluminous ferrocyanide of peroxide of iron with an alkali. Possessing the nature and properties of burnt Sienna, it is transparent, permanent, and dries well in oil. Of an orange hue, it is neither so rich nor so powerful as that pigment, and is better employed as a glaze than in body.

255. SEPIA,

_Liquid Sepia_, _Seppia_, or _Animal aethiops_, is named after the sepia or cuttle-fish, also called the ink-fish, from its affording a dark liquid, which was used as an ink and pigment by the ancients. All the species of cuttle-fish are provided with a dark-coloured fluid, sometimes quite black, which they emit to obscure the water, when it is wanted to favour their escape from danger, or, by concealing their approach, to enable them with greater facility to seize their prey. The liquid consists of a ma.s.s of extremely minute carbonaceous particles, intermixed with an animal gelatine or glue, and is capable of being so widely spread, than an ounce of it will suffice to darken several thousand ounces of water. From this liquid, brought chiefly from the Adriatic, but likewise obtainable from our own coasts, is derived the pigment sepia, as well as, partially, the Indian ink of the Chinese.

Sepia is a powerful dusky brown, of a fine texture, transparent, works admirably in water, combines cordially with other pigments, and is very permanent. It is much used as a water-colour, and for making drawings in the manner of bistre and Indian ink; but is not employed in oil, as it dries therein very reluctantly. Extremely clear in its pale tints, and perhaps the best washing colour known, sepia must be used with caution, or otherwise heaviness will be engendered in the shades, so strong is its colouring property. Mixed with indigo, or, preferably, Prussian blue and black, it is eligible for distant trees, for a general shadow tint in light backgrounds, and for the shade of white linen or white draperies. With madder red it forms a fine hue, somewhat resembling brown madder, and with crimson lake and indigo gives an artistically excellent black. Sometimes alone and sometimes in combination with lamp black, or madder red and Prussian blue saddened by the black, it will be found useful in dark foreground boats, rocks, near buoys, sea-weed, &c.

Compounded with aureolin, sepia yields a series of beautiful and durable neutral greens for landscape; and mixed with Prussian blue, affords low olive greens, which may be deepened into very cool dark greens by the addition of black. For hills and mountains in mid-distance, sepia combined with cobalt and brown madder is of service; or, for the dark markings and divisions of stones in brooks and running streams, the same compound without the cobalt. Mixed with purple madder, it furnishes a fine tint for the stems and branches of trees; and with French blue and madder red gives a really good black. Compounds of sepia and yellow ochre, gamboge, raw Sienna, or cobalt and aureolin, are severally useful. A rich and strong brown is formed by the admixture of madder red, burnt Sienna, and sepia; a tint which may be modified by omitting the sepia or the Sienna, or reducing the proportions of either. For Dutch craft, this tint and its variations are of great value. A wash of sepia over green very agreeably subdues the force of the colour.

256. WARM SEPIA

is the natural sepia warmed by mixture with other browns of a red hue, and is intended for drawings where it would be difficult to keep the whole work of the same tint, unless the compound were made in the cake of colour.

257. ROMAN SEPIA

is a preparation similar to the preceding, but with a yellow instead of a red cast.

258. VANd.y.k.e BROWN.

This pigment, hardly less celebrated than the great painter whose name it bears, is a species of peat or bog-earth of a fine, deep, semi-transparent brown colour. The pigment so much esteemed and used by Vand.y.k.e is said to have been brought from Ca.s.sel; an a.s.sertion which seems to be justified by a comparison of Ca.s.sel earth with the browns of his pictures. Gilpin in his Essays on Picturesque Beauty, remarks that "In the tribe of browns--in oil-painting, one of the finest earths is known, at the colour shops, by the name of Castle-earth, or Vand.y.k.e's brown." The Vand.y.k.e brown of the present day is a bituminous ochre, purified by grinding and washing over. Apt to vary in hue, it is durable both in water and oil, but, like all bituminous earths, dries tardily as a rule in the latter vehicle. Clear in its pale tints, deep and glowing in shadows, in water it has sometimes the bad property of working up: for this reason, where it is necessary to lay on a great body of it, the moist tube colour should be preferred to the cake. With madder red, the brown gives a fine tint, most useful as a warm shadow colour; and with Prussian blue, clear, very sober neutral greens for middle distances. In banks and roads, Vand.y.k.e brown is the general colour for dragging over the surface, to give roughness of texture: compounded with yellow ochre, it affords a good ground tint, and with purple madder a rich shadow colour. In sunrise and sunset clouds, a mixture of the brown with cobalt yields a cold neutral green, adapted for those clouds at the greatest distance from the sun. For foliage tints, aureolin, French blue, and Vand.y.k.e brown, will be found of service; or as a glaze over such tints, the yellow and the brown. With raw Sienna, brown madder, Payne's gray, gamboge, and Roman ochre, this brown is useful. In a water-colour winter scene, when the trees are denuded of foliage, the net work of the small branches at the tops of them may be prettily given with cobalt and Vand.y.k.e brown, used rather dry, and applied with a brush having its hairs spread out either by the fingers or by drawing them through a fine-tooth comb before working. Gra.s.s is likewise represented readily by this means, and so are small trees on the summit of a cliff or in like positions.

The Campania Brown of the old Italian painters was a similar earth.

259. VERONA BROWN,

a pigment peculiar to oil painting, is a native ferruginous earth. A citrine brown of great service in tender drab greens, it forms with terre verte and the madder lakes rich autumnal tints of much beauty and permanence.

260. YELLOW MADDER,

_Cory's Yellow Madder_, or _Cory's Madder_, is cla.s.sed among the browns for the same reason that Italian Pink was ranked among the yellows. It was stated in the eighth chapter that no true madder yellow, brilliant and pure, exists as a pigment at the present day, and certainly this preparation can lay no claim to the t.i.tle. Except in name, it is an orange-brown of the burnt Sienna hue, and might therefore with more reason have been called Orange Madder. It is a good and permanent colour, rich and transparent, at present used only in oil, we believe, and chiefly as a glaze.

261. _Cadmium Brown_.

By igniting the white carbonate of cadmium, among other methods, a cinnamon-brown oxide is obtainable, of a very clear and beautiful colour if the process be well conducted. It is, however, not eligible as a pigment, owing to the rapidity with which the oxide is acted upon by the air. In water, especially, we have found this brown so eagerly absorb carbonic acid from the atmosphere as to become in a few months once more a carbonate, and as purely white as before. The same result is observable when the powder is exposed: some shown at the International Exhibition of 1862, on a gla.s.s stand, had to be removed, its label marked 'Cadmium Brown' being at last found attached to a sample of cadmium white. In oil, the conversion takes place less readily, that vehicle having the property of protecting, to some extent, pigments from oxidation. It is curious that even in a book a water-rub of the brown slowly but surely changes to white.

262. _Catechu Browns._

Catechu is an extract of the Khair tree or _acacia catechu_ of Bombay, Bengal, and other parts of India. With the exception of such earthy matters as are communicated to it during the preparation, or are added purposely as adulterants, catechu is entirely soluble both in water and alcohol. An aqueous solution has a reddish-brown colour, and gives the following results:--protosalts of iron thrown down olive-brown and persalts greenish-brown precipitates; salts of tin and lead yield brownish-yellow and brick-coloured deposits respectively; while acetate of copper or bichromate of potash furnishes brown residues. To our knowledge, none of these have been introduced as pigments, but a brown prepared by Dr. Lyon Playfair some years back from the catechu bark has been described as exceedingly rich, transparent, and beautiful; and recommended for painting _if not too thinly applied_.

263. _Chrome Browns_

are produced by various methods of several hues, tints, and shades, both by wet and dry processes. We have obtained them by many methods, of different degrees of permanence. Some very intense in colour have stood well, while others paler and more delicate have gradually greened, but none possessed the strict stability of the green oxides. Presuming a paucity of browns, these preparations of chromium would be worth further attention; but, with the objection of being--for browns--somewhat expensive, they have the far more fatal objection of not being wanted.

264. _Copper Brown_,

varying in hue, is obtainable, in the form of prussiate, &c., but cannot be recommended, however made.

265. _French Prussian-Brown._

According to Bouvier, a colour similar to that of bistre, and rivalling asphaltum in transparency, is produced by partially charring a moderately dark Prussian blue; neither one too intense, which gives a heavy and opaque brownish-red, nor one too aluminous and bright, which yields a feeble and yellowish tint. Yielding to a rapture we cannot wholly share, he describes its qualities in the warmest terms. In his opinion, it has the combined advantages of asphaltum, mummy, and raw Sienna, without their drawbacks. "I cannot," he says, "commend too highly the use of this charming bistre-tint: it is as beautiful and good in water as in oil, perfectly transparent, of a most harmonious tone, and dries better than any other colour suitable for glazing. Closely resembling asphaltum in tint as well as in transparency, this brown is preferable to it in every point of view." As the colour is very quickly and easily obtained, the artist can judge for himself of its proper value. M. Bouvier's process is, to place upon a clear fire a large iron spoon, into which, when red hot, some pieces of the Prussian blue are put about the size of a small nut: these soon begin to crackle, and throw off scales in proportion as they grow hot. The spoon is then removed, and allowed to cool: if suffered to remain too long on the fire, the right colour will not be produced. When the product is crushed small, some of it will be found blackish, and the rest of a yellowish brown: this is quite as it should be. Chemically, the result is a mixture of oxide of iron and partly undecomposed or carbonised prussiate.

266. _Gambogiate of Iron._

Dr. Scoffern read a paper at the Meeting of the British a.s.sociation of Science, in 1851, describing this combination as a rich brown, like asphaltum, but richer, as well as more durable in oil. It has not been, however, employed as a pigment, or at least is not at present.

267. _Hypocastanum_,

or Chestnut Brown, is a brown lake prepared from the horse-chestnut.

This now obsolete pigment is transparent and rich in colour, warmer than brown pink, and very durable both in water and oil; in the latter of which it dries moderately well.

268. _Iron Browns_,

native or artificial, are well represented on the palette, but nothing would be easier than to increase their number. Of all metals, iron is the richest source of colour, capable of affording all colours with the exception of white. None of them, however, are so numerous as the browns, a description of which would fill this chapter. Suffice it to state they are obtainable of every hue, tint, and shade, and are generally permanent. They are made on a large scale and sold under various names for house-painting, &c.

269. _Manganese Brown_

is an oxide of manganese, which is quite durable both in water and oil, and dries admirably in the latter. A fine, deep, semi-opaque brown of good body, it is deficient in transparency, but might be useful for glazing or lowering the tone of white without tinging it, and as a local colour in draperies, &c.

270. _Nickel Brown._

A very pleasing yellowish brown is obtainable from nickel, bright and clear in its pale washes, and of some richness in oil. Unless thoroughly washed, it has a tendency to greenness in time.

271. _Ochre Browns._

The slight affinity of sulphur for yellow ochre, with its merely temporary effect thereon, was observed in the eighth chapter, where allusion was made to the action of sulphuretted hydrogen and sulphide of ammonium on the earth. Sulphur alone, and in the dry state, ignited with yellow or other native ochres converts them into browns, varying in hue, and of greater or less durability. Those browns, however, which we have made by this process, although standing well in a book, have not withstood exposure to light and air. They have all become pale, whitish, or of a drab cast, evidently through the oxidation of the sulphur, or rather the sulphide of iron formed during the calcination. Practically, therefore, ochres have an antipathy to sulphur, moist or dry, by itself or in combination; and are, so to speak, the disinfectants of the palette. Ever waging war against sulphurous vapours, the native earths serve to protect a picture from the damaging influence of impure air, whether they be used alone, or employed in admixture with such pigments as are injured thereby.

272. _Purple Brown_

is a refuse manufacture from Indian red washings. A dull, heavy, coa.r.s.e colour, it belongs to the cla.s.s of common pigments which are unexceptionable for decorative painting, but scarcely suited to the higher branches of art. As this work professes simply to treat of artistic pigments, that have been, are, or might be, more than a pa.s.sing reference to those colours exclusively adopted by house-painters, &c., would be out of place.

273. _Rubens' Brown_,

still in use in the Netherlands under this appellation, is an earth of a lighter colour and more ochrous texture than the Vand.y.k.e brown of English commerce: it is also of a warmer or more tawny hue than the latter pigment. Beautiful and durable, it works well both in water and oil, and much resembles the brown employed by Teniers.

274. _Uranium Brown._

Yellow, red, orange, green, have been previously noticed as being derived from uranium, and to this list of colours may now be added brown. A warm rich hue of the utmost intensity may be produced, which possesses considerable permanence, although not equal to that of uranium yellow.

275. _Zinc Brown._