Catechu (Cutch) is an old Indian dye for cotton. It can also be used for wool and silk, and gives a fine rich brown. It is obtained from the wood of various species of Areca, Acacia and Mimosa trees. Bombay Catechu is considered best for dyeing purposes.
Catechu is soluble in boiling water. It is largely used by the cotton dyer for brown, olive, drab, grey and black. (See pp. [46], [47], [48].)
LIGHT GREY
(For 6 lbs.) 1 oz. cutch, 1 oz. iron. Boil for 1/2 an hour in the cutch, then put into boiling iron, being very careful to stir well. Wash very thoroughly.
These proportions can be varied according to the shade of grey required; the more iron makes the colour browner, the more cutch the bluer grey.
CATECHU BROWN
The wool is boiled for 1 to 1-1/2 hours, with 10 to 20 per cent catechu, then sadden with 2 to 4 per cent of copper sulphate, ferrous sulphate, or chrome, at 100°C., in a separate bath for 1/2 hour.
ALDER BARK
The bark and twigs of alder are used for dyeing brown and black. For 1 lb. wool use 1 lb. alder bark. Boil the wool with it for 2 hours, when it should be a dull reddish brown. Add 1/2 oz. copper as for every pound of wool for black.