13). Scarlet for Silk.
After boiling and washing, the silk is first slightly dyed with yellow by working it for ¼ hour at 50°C., in a weak soap bath containing about 10 per cent. of Annatto; it is then well washed. Mordant the silk by working it for ½ hour, then steeping it over night in a cold solution of 40 per cent. of nitro-muriate of tin. Wash and dye in a fresh bath with a decoction of 20 to 40 per cent. of cochineal and 5 to 10 per cent. cream of tartar. Enter the silk at a low temperature and heat gradually to boiling. Brighten in a fresh bath of cold water, slightly acidified with tartaric acid. Good results can also be obtained with the single bath method with cochineal, stannous chloride and oxalic acid.
With the use of iron mordants very fine shades of lilac may be obtained on silk with cochineal.
LAC DYE.
Like Cochineal and Kermes, Lac is a small scale insect, Coccus lacca. It is found in India, Burmah and other Eastern countries; it was introduced into England in 1796.
The method of dyeing with lac is very much the same as with cochineal; it yields its colour less readily however, and should be ground into a paste with the tin solution employed and a little hydrochloric acid and allowed to stand for a day before using. It is said to be a faster dye than cochineal, but is often used in combination with it, being a fuller colour though not so bright.
A good fast scarlet is produced by the following recipe:—For 100 lbs. wool. 8 lbs. lac, previously ground up with part of the tin spirits, 5 lbs. cochineal, 5 lbs. tartar, 20 lbs. tin spirit.
MADDER.
Madder consists of the ground up dried roots of a plant, (Rubia tinctorum) cultivated in France, Holland, and other parts of Europe, as well as in India. Madder is not much used for silk dyeing, but for wool, linen and cotton it is one of the best dyes. It is also used largely in combination with other dyes to produce compound colours. When used for cotton the colour is much improved by boiling in a weak solution of soap after the dyeing. The gradual raising of the temperature of the dye bath is essential in order to develop the full colouring power of madder; long boiling should be avoided, as it dulls the colour. If the water is deficient in lime, brighter shades are got by adding a little ground chalk to the dye bath, 1 to 2 per cent.
Berthollet distinguishes two kinds of madder red on cotton, one of which is given in [No. 4]. The other is the well-known Turkey red or Adrianople red, a very difficult and complicated dye, but one of the most permanent dyes known. Madder reds are said to be not so beautiful as those from Kermes, lac or cochineal, but my experience has been that with care, the finest reds can be got with madder.