Note 8 — PART II.
Reading edition
Schutzenberger gives the following receipts:—
PREPARATION FOR DISCHARGE.
Water 2 litres.
Yellow chromate 500 grammes.
WHITE DISCHARGE ON BLUE BOTTOM.
Tartaric acid 3 kilograms.
Oxalic acid 250 grammes.
Burnt starch 4 kilograms.
Nitric acid 500 grammes.
Water 4 litres.
De Kæppelin gives the following:—
WHITE DISCHARGE ON BLUE.
Water 2 litres.
Starch 1 kilogram, 800 grammes.
Oxalic acid 500 grammes.
Tartaric acid 250 grammes.
Sulphuric acid 375 grammes.
The pieces, having been dyed blue, are then placed in a solution of bichromate of potash in water, which is prepared in the ratio of 50 to 60 grammes to the litre, according to the intensity of the blue. The pieces thus prepared must be dried away from direct solar light or too much heat. In fact, under the action of these agents, the bichromate would be decomposed and the tissue altered. The pieces are often rolled up to prevent this effect. After the pieces are printed, they are passed into a vessel containing water and holding chalk in suspension in sufficient quantity to give it a milky aspect. The temperature of the bath is raised to 60° R. The excess of acid of the color applied is saturated by the chalk, and the excess of bichromate of potash with which the tissue is impregnated is dissolved in the bath. The pieces are afterwards washed and passed through slightly soapy water.