To produce two shades of the blue with a green, the cloth is vatted to a pale-blue, a white reserve for light shades, and an orange reserve, are printed in. The usual operations are then gone through ; but after the bichromate process, the pieces are taken through nitric acid, which must be very dilute, otherwise the indigo may be destroyed. The result is a dark-blue ground, with a design in pale-blue, where the white resists have been applied, and in green, whore the orange has been printed.
The following are examples of compositions for produoing a design by discharging a vat-blue ground.
Red and White discharges on Vat-Blues.—Give a medium blue in the vat. Steep pieces in bichrt ornate of potash, 41. oz. in 1Q pint water, and dry on rollers, avoiding sun-light. Print on the following discharges:— White discharge.—Water, 7 pints; white starch, 2 lb. 71 oz. Boil, and add while still warm, 2 lb. S oz. tartaric) acid, and then 21i oz. oxalic acid, dissolved in If pint water.
Red disoharge.—Red liquor, 14 qt. ; white starch, 171 lb. Boil ; let one half grow cold, and add to it 7 lb. 10 oz. oxalic acid. Then add the other half of the hot mixture to complete the solu tion of the acid.
Preparation of the Red Liquor.—Alum, 2 lb. 3 oz.; acetate of lead, the same weight ; water, 3} pints. Print on the white and red discharges with the perrotine, or with a two-colour cylinder machine. Do not dry too strongly. Age in hot, but not moist, air, which is an essential condition. The next morning, dung as follows :—Into a beck with rollers, put 6 lb. 9 oz. neutral arsenate of potash, 27 lb. 7 oz. chalk, and 1750 pints water. Pass the pieces slowly through at a simmer, so as to keep the chalk in suspension. After leaving this beck, the pieces are strongly compressed between two rollers covered with cloth. After the first five pieces have passed, feed the beck with 1 oz. arsonists of potash, and a little chalk, per piece. After thus cleansing the pieces, dye up in amine, and take through boiling water.
Green and Yellow on a Deep-blue Ground.—Boil the pieces with 2 lb. 3 oz. soda-ash per 100 yds. ; wash well, and take through a weak soda beck, containing per 100 yds., 81 oz. soda-ash at 38° (100° F.). Dry, calender, and dye a blue in the cold vat. Take through sulphuric acid at 1.4° Tw., starch slightly, dry, and calender cold. Print the following colours on the blue ground : (1) Green Discharge.-26t lb. pipe-clay, 6 lb. 9 oz. gum arabie, the same weight of blue-stone, and of verdigris, 13 lb. 2 oz. nitrate of lead, and 6 lb. 9 oz. sugar of lead. The verdigris is dis solved in acetic acid, and the gum in water ; the two solutions are stirred together, and the pipe clay, previously softened in water, is added. The other ingredients are powdered, and stirred in by degrees. Water is added, enough to make the mixture fit for printing; when it is boiled, the water lost by evaporation is replaced, and the colour is then ready.
(2) Yellow Discharge.—Pipe-clay 19 lb. 11 oz. ; verdigris, 21 lb. ; blue-stone, 2 lb. 71 oz.; nitrate of copper, 3} lb.; the same weight of gum arabio, 15i pints water, 61 lb. nitrate of lead, the same weight of sugar of lead, and 4 lb. 6 oz. nitric acid, at 143° Tw. Make up the colour without the nitric acid, stir all well together, and stir in the nitric acid just before using.
Print on first the green and then the yellow. Age in the cold, till the discharge becomes visible on the back of the pieces. Take them through a weak vat to wet them, and then dye up to shade in a fresh vat. Sour without drying, wash off the colours, rinse, take through weak lime water to remove the acid, and then through a beck of chromate of potash, containing 3i lb. chro mate per 87 qts. water. The pieces are caused to move very slowly, so that the dyeing process may go on satisfactorily. Rinse, dry, stiffen, and calender.