The indigo vat for wool and silk is mounted exclusively with indigo, good potashes of commerce, m adder, and bran. In this vat, the immediate principles with base of carbon and hydrogen, such as the extracts of madder and bran, perform the disoxydising function of the copperas in the cold vat. The pastel vats require most skill and experience, in consequence of their complexity. The greatest diffi culty occurs in keeping them in a good condition, because they vary progressive ly as the dyeing goes on, by the abstrac tion of the indigotine, and the modifica tion of the fermentable matter employed to disoxygenate the indigo. The alkaline matter also changes by the action of the air. By the successive additions of indi go, alkali, &c., this vat becomes very difficult to manage with profit and suc cess. The great affair of the dyer is the proper addition of lime ; too much or too little being equally injurious.
Sulphate of indigo, or Saxon blue, is used also to dye silk and wool. If the wools be ill sorted, it will show their dif ferences by the inequalities of the dye. Wool dyed in this bath put into water saturated with sulphureted hydrogen, be comes soon colorless, owing to the disox ygenation of the indigo. The woollen cloth when exposed to the air for some time resumes its blue color, but not so intense ly as before.
Logwood. The properties of hema tine explain the mode of using logwood. When stuffs are dyed in the infusion or decoction of this wood, under the influ ence of a base which acts upon the hema tine in the manner of an alkali, a blue dye, bordering upon violet, is obtained.
Such is the process for dyeing cotton and wool a logwood blue by means of verdi gris, crystallized acetate of copper, and acetate of alumina.
When we dye a stuff yellow, red, or orange, we have always bright tints : with blue, we may have a very dark shade, but somewhat violet; the proper black can be obtained only by using the three colors, blue, red, and yellow in proper proportions. Hence we can explain how the tints of yellow, red, orange, blue, green, and violet, may be browned, by applying to them one or two colors which along with themselves would produce blAk ; and also we may explain the na ture of that variety of blacks and grays which seems to be indefinite. Nutgalls and sulphate of iron, so frequently em ptoyed for the black dye, give only a vio let or bluish gray. The pyrolignite of iron, which contains a brown empyreu matic matter, gives to stuffs a brown tint, bordering upon greenish yellow in the pale hues, and to chestnut brown in the dark ones. By galling cotton and silk, and giving them a bath of pyrolignite of iron, we may, after some alternations, dye them black. Galls, logwood, and a salt
of iron, produce merely a very deep vio let blue ; but by boiling and exposure to the air, the hematate of iron is changed, becoming red-brown, and favors the pro duction of black. Galls and salts of cop per dye stuffs an olive drab, logwood and salts of copper, a violet blue ; hence their combination should produce a black. In using sumach as a substitute for galls, we should take into account the proportion of yellow matter it con tains. When the best possible black is wanted upon wool, we must give the stuff a foundation of indigo, then pass it it into a bath of logwood, sumach, and proto-sulphate of iron. The sumach may be replaced by one third of its weight of nu galls.
The compound or mixed colors, are Such as result from the combination of two differently colored dye-stuffs, or from dyeing stuffs with one color, and then with another. The simple colors of the dyer are red, yellow, blue, and black, with which, when skillfully blended, lie can produce every variety of tint. Ber haps the dun or fawn color might be ad ded to the above, as it is directly ob tained from a great many vegetable sub stances.
1. Red with yellow, produces orange ; a color which, upon wool, is given usual ly with the spent scarlet bath. To this shade may be referred flame color, pome granate, capuchin, prawn, jonquil, cassia, chamois, café au hint, aurora, marigold, orange peel, mordorh, cinnamon, gold &e. Snuff, chestnut, musk, and other shades are produced by substituting wal nut peels or sumach for bright yellow. If a little blue be added to orange, an olive is obtained. The only direct orange dyes are annotto, and subchromate of lead (see Situ AND WOOL Draixo).
2. Red with blue produces purple, vio let, lilac, pigeon's neck, mallow, peach blossom, bleu de rod, lint-blossom, ama ranth.
3. Red with black ; brown, chocolate, marone, &c.
4. Yellow with blue; green of a great variety of shades, such as nascent green, gay green, grass green, spring green, laurel green, sea green, celadon green, parrot green, cabbage green, apple green, duck green.
5. Mixtures of colors, three and three, and four and four, produce an indefinite diversity of tints; thus, red, yellow, and blue, form brown olives, and greenish grays ; in which the blue dye ought al ways to be first given, lest the indigo vat should be soiled by other colors. Red, yellow, and gray, (which is a gradation of black), give the dead-leaf tint, as well as dark orange, snuff color, &c. Red, blue, and gray, give a vast variety of shades ; as lead gray, slate gray, wood pigeon gray, and other colors, too nume rous to specify.