15). To Dye Indigo Blue.—Potash Vat.—
Into a pot 3 parts full of water put 1½ oz. Madder and 1½ oz. bran. Heat to nearly boiling, and keep at this heat for 3 hours. Then add 5 oz. Carbonate of Potash; allow Potash to dissolve and let the liquor cool down till luke-warm. Then add 5 oz. thoroughly ground Indigo, stir well and leave to ferment for two days, occasionally stirring, every 12 hours or so. Wool dyed in this vat must be thoroughly washed after the colour is obtained.
Process of Dyeing.—Into a vat prepared as above, dip the wool. Keep it under the vat liquor, gently moving about a sufficient time to obtain the colour required. A light blue is obtained in a few seconds, darker blues take longer. Take out wool, and thoroughly squeeze out of it all the dye liquor back into the vat. Spread out the wool on the ground, exposed to the air till the full depth of colour is developed. The wool comes out of the vat a greenish shade, but the oxygen in the air darkens it, through oxydation, to indigo blue. The wool should now be washed in cold water with a little acid added to it, and again thoroughly rinsed and dried.
16). Blue Vat for Cotton.—
In a clean tub put 10 pails of water, slacken 1 bushel of lime into it, and cover while slackening; put 6 lbs. ground Indigo in a pot and mix it into a paste with hot water and then put 4 pails of boiling water on to it, stir it, cover it, and leave it. In another pot, put 20 lbs. copperas, pour 4 pails of water on this, stir it and leave it covered. Pour 4 pails of water on the top of the lime that is slackening, rake it up well and put in the melted copperas; rake it well and put in the Indigo; stir well and leave covered for a couple of days, stirring occasionally. Half fill a new vat with the mixture. Rake it well and while you are raking, fill it up with clean water, continue raking for an hour. Cover it over; it can be used the next day. This is a colour that never washes out.
17). Gloucestershire Indigo Vat.
Size 5 feet over the top: 7 feet deep, 6 to 7 feet at the bottom.
Take ½ cwt. bran, ¼ peck lime and 40 lbs. indigo. Warm up to 180 to 200°F., rake it 4 times a day. If it ferments too much add more lime: if not enough, more bran. An experienced eye or nose will soon tell when it is ripe or fit to use, which should be in about 3 days. Regulate the strength of the vat from time to time to the colour required. No madder or woad is used when much permanency is wanted.
18). Cold Indigo Vat for Dyeing Wool, Silk, Linen and Cotton.
1 part Indigo, 3 parts good quicklime, 3 parts English vitriol, and 1½ parts of orpiment. The Indigo is mixed with water, and the lime added, stirred well, covered up, and left for some hours. The powdered vitriol is then added, and the vat stirred and covered up. After some hours the orpiment powder is thrown in and the mixture is left for some hours. It is then stirred well and allowed to rest till the liquid at the top becomes clear. It is then fit for dyeing.