8. Violet mordants.—These consist either of a very weak solution of acetate of iron, of spec. gravity 1·007, for example; or of a little of the stronger acetate of 1·04, mixed with acetate of alumina, and a little acetate of copper, thickened with starch or British gum. The shades may be indefinitely varied by varying the proportions of the acetates.
When black is one of the colours wanted, its mordant is very commonly printed-on first, and the goods are then hung upon poles in the drying-room, where they are aired for a few days, in order to fix the iron by its peroxidizement; the mordants for red, violet, &c., are then grounded in, and the pieces are dyed up, after dunging and washing, in the madder bath, into which, for certain shades, sumach, galls, or fustic, is added. The goods are brightened with a boil in soap water; occasionally also in a bath, containing a small quantity of solution of tin or common salt. The following mode of brightening is much extolled by the French, who are famous for their reds and roses.
1. A soap boil of forty minutes, at the rate of 1 pound for every 2 pieces. Rinse in clear water.
2. Pass through chloride of soda solution of such strength that two parts of it decolour one part of Gay Lussac’s test liquor. See [Chloride of Lime] and [Indigo]. Wince the pieces through it for 40 minutes. Rinse again.
3. Pass it again through the soap bath, No. 1.
4. Brighten it in a large bath of boiling water, containing 4 pounds of soap, and 1 pound of a cream-consistenced salt of tin, containing nearly half its weight of the muriate of tin, combined with as much nitric acid of spec. grav. 1·288. This strong nitro-muriate having been diluted with a little water, is to be slowly poured into the bath of soap water, and well mixed by stirring. The pieces are now put in, and winced through it for one half, or three quarters of an hour.
5. Repeat the soap boil, No. 1. Rinse and dry.
9. Grounding in of Indigo blue.
Take half a gallon of water of 120° F., 8 ounces of ground indigo, and 8 ounces of red sulphuret of arsenic (orpiment), 8 ounces of quicklime, mix together, and heat the mixture to the boiling point; withdraw from the fire, and add, when it is lukewarm, 6 ounces of carbonate of soda, stir and leave the whole at rest till the next day. Then decant the clear liquor, and thicken every quart of it with half a pound of gum. This colour ought to be green, and be preserved in a close vessel. When used it is put into a pot with a narrow orifice, the pencil is dipped into it, wiped on the edge of the pot, and immediately applied by hand. This plan is tedious, and is nearly superseded by the following grounding blue.
Take half a gallon of caustic soda lye of spec. grav. 1·15, heated to 120° F.