BLUE.--Indigo dissolved in sulphuric acid, to which is added alum, forms a basis of most blues and was used long before the Christian era. It is obtained from the leaves of various specimens of Indigofera which are cultivated largely in India. The deep Persian blue is obtained by applying indigo over madder. It can be compounded with almost any other dyeing material known and it is by this mixing process that beautiful violets, porcelain blues and pinks are obtained. A superb dark blue found in some of the antique Persian rugs has been in disuse for nearly a half century. The secret of making it seems to have been lost and no one has been able to reproduce it.
GREEN.--Indigo in combination with one of the yellows furnishes most of the greens. With buckthorn it produces Chinese greens, both bright and dull.
BROWN.--Browns are most frequently obtained by mixing madder with yellow or by dyeing with madder over yellow. Valonia, catechu, gall-nuts, and the green husks of walnuts also enter largely into the making of browns.
YELLOW.--The principal yellows are obtained from the Persian berries, from turmeric, from saffron and sumac roots. Persian berries give a fast dull yellow. Turmeric is from the root of a plant growing abundantly in East India and China and it gives a bright orange color. Orange yellow is also obtained from henna and by combining madder and turmeric. A light yellow is obtained from larkspur; a greenish yellow from a fungus of the mulberry, and, of late years, a buff colored yellow has been obtained from quercitron bark.
BLACK.--Black seems to be the only color which the rug makers of older days were unable to produce from vegetable or animal sources. The principal black used was that made from iron filings with vinegar and pomegranate rind, but it destroyed the fibres of the wool. For this reason very little black was used in the antique pieces excepting where the fleece of black sheep could be obtained. Nowadays logwood, which grows in Central America, is the essential basis of all blacks in wool, although other colors are frequently used with it to modify or intensify the shade.
PURPLE.--From very early times the Phœnicians were renowned for a purple which they obtained from a shellfish found in the Ægean Sea, but the secret of making it has long since become a lost art. A great many shades of purple, heliotrope and lavender are obtained from the different red dyes in combination with indigo and the dye woods as well as from the bodies of marine insects and mollusks.