To dye wool PEACH.
This process is the same as the last; that is, after scarlet; but the wool is not to be alumed: in some cases, a little tartar and cochineal is added.
Observe, that the cochineal and tartar being added, the previous preparation must be according to the fulness or faintness of the shade wanted, whether of buff, peach, or flesh, all of which require, essentially, the same process. By such means, a pattern of any shade, compounded of red and yellow, from scarlet to the weakest buff and flesh, may be produced.
To set an indigo vat for worsted, serge, &c.
The vat being five feet high, and two feet in diameter at top, you may use for it from two to six pounds of indigo, according as you set it light or full.
Boil two pounds of potash, two ounces of madder, and a handful of bran, in fifteen gallons of clear soft water, for half an hour.
The indigo must be powdered; after which it must be levigated in a peculiar circular cast-iron mill, having a contrivance for two large round stones, or cast iron balls, which are kept in a perpetual circular motion while the indigo is ground. Water it, and put it into the mill, and as the balls run round, the indigo in the water is reduced to a fine flowery paste. There are mills more convenient than these, but, perhaps, none more simple for a small concern.
When the indigo is thus prepared, boil it in the copper with the grounds of the madder and the potash, which fell to the bottom; it is all, then, to be put into the vat at the same time with the indigo; the whole is to be stirred, the vat covered, and heat applied to make it more than blood warm, and to keep it so. The vat should be stirred twice, slightly, both the second and third day, the heat remaining the same; when a brassy scum, divided and interrupted in many places, begins to appear on the surface. On the fourth day, the heat being continued, the scum becomes more perfect and less broken, the froth which rises, upon stirring, is more blue, and the vat a deep green.
When it becomes green in this manner, it is an indication that it must be filled; to do which, boil half an ounce of madder, and one pound of potash, in five gallons of water; put in this liquor, and stir it; if it produce much froth, stir it again, and the next day it will be fit for working; which, however, will be sufficiently known by the quantity of froth, and by the brassy and scaly crust on the surface of the liquor, on blowing or stirring which, the liquor beneath is green, although the surface appears brown or blue.
When the vat has worked about forty or fifty pounds of serge or worsted, it may be necessary to replenish it with one pound of potash, half an ounce of madder, and a handful of bran; these being boiled a quarter of an hour, are added to the vat.
When this vat wants replenishing with indigo, which may be known by the liquor being no longer green, but brown, blue, or almost black, two-thirds of it must be put into a copper; when ready to boil, the scum on the top must be taken off by a sieve, after which it should be suffered to boil, with the addition of two handfuls of bran, a quarter of a pound of madder, and two pounds of potash; soon after it has boiled, it is to be put into the vat with one pound of indigo, prepared as before; the vat being again stirred, and covered, the heat always remaining between blood and fever heat.
When an indigo vat has been several times re-heated, it should be emptied out entirely, and set anew, because the colour becomes dull. The preceding process is from Hellot.
[8] It is necessary that the student should not confound the terms primitive colours here with the prismatic or primary colours, for the discovery of which we are indebted to Sir Isaac Newton. See the Introductory Chapter.
CHAPTER V.
ON DYEING SILK AND COTTON BLACK, &c.
To dye silk black for velvets—To dye silk black, London process—On dyeing cotton black at Rouen—To dye cotton black, London process—For dyeing black, particularly cotton velvets, at Manchester—On dyeing silk and cotton black, with a blue ground—Another iron liquor—To dye cotton black, by using the preceding solution—To dye cotton violet—To dye cotton red—To dye cotton an Adrianople or Turkey red—Miscellaneous observations relative to Adrianople red.
Some of the more simple and less difficult processes of dyeing both cotton and silk, are described in the preceding chapters; we shall now describe those, not only for black, but for some other colours, which require more care and attention. For ungumming and boiling silk, &c. see Chap. VI.
Silk has a strong affinity for galls, and advantage is sometimes taken of this: for silk, being a valuable article, is often galled to excess, merely to increase its weight.
Cotton has a strong affinity for iron, and iron has the same for gallic acid, wherever it may be found; therefore, in sumach, alder-bark, &c., iron unites with the acid, whenever both are connected by the medium of water. Tannin, doubtless, has also some share in such dyeing processes, although what does not even now appear to be well understood.
Black, Macquer observes, is rather difficult to be dyed upon silk; or, at least, there is reason to think so, from the numberless experiments which have been found necessary to the attainment of a good black, as well as from the multitude of heterogeneous ingredients which Macquer admitted into the composition of his various processes for this dye, some of which consisted of arsenic, corrosive sublimate, litharge, antimony, plumbago, and about ten other ingredients! we shall not, therefore, detail such preposterous mixtures; one, however, we may just put down by way of showing what the art was in Macquer's time.
Take twenty quarts of strong vinegar, one pound of black nut galls pounded, and five pounds of iron filings; these ingredients are to be mixed in one vessel.