DYES, NATURAL. The utilization of plant products for dyeing is of ancient origin, and without doubt at the first con sisted in the staining of material with the coloured juices of fruits, flowers and the like. It would be observed that certain of these effects resisted the washing process, a true fixation of the colour having occurred, and such discoveries would in course of time be extended; but on the other hand few substantive dyestuffs exist in nature, the variety of shade they yield is limited, and their effects in the main are not permanent in sun light. Again, the observation that the leaf juice of the indigo plant develops a blue colour on keeping, and that the sea-snail, Murex, when crushed and exposed to light acquires a purple tint, would prepare the way for the subsequent application to fabrics of both the indigo and the purple of the ancients. The process of isolating indigo from the plant was no doubt preceded by a practice of developing this colouring matter in the leaf itself and the employment of the latter as such in the dyeing process, a method which is still adopted in remote parts of China and Africa.
The antiquity of the use of indigo is evident from the dis covery at Thebes of a garment dyed therewith, of date about 300o B.e., whilst the words "blue" and "purple" occurring in Exodus, xxv. 4, and xxxv. 25, can hardly refer to colours other than indigo and the Murex purple. The latter, also known as "Tyrian" or "royal" purple, was of much importance, and the city of Tyre where, according to legend, it was discovered, be came famous for its production. The Scriptural quotation "clothed in purple and fine linen" refers not only to this dyestuff but also to its expensive character. It was only as the result of the discovery of the art of mordanting, however, which occurred (probably in India) not later than 2000 B.C., that the practice of dyeing really advanced, for as a result many natural colouring matters otherwise useless could be applied to fabrics. Thus the Biblical scarlet without doubt refers to the colour given by kermes on alum-mordanted material, whereas both madder and the lac dye of India, which have been in use from time immemorial for red dyeing, only give this colour to fabrics which have been similarly treated. Very ancient too is the use of "archil," a colour resulting from the action of ammonia as stale urine on certain lichens, and referred to by Pliny as of service in rein forcing the shade of the Tyrian purple. Early references to mordant yellow dyestuffs are meagre, though according to the same author, "cotinus" (evidently the shrub Rhus cotinus, that is, young fustic and weld, which was the more valuable of the two) was in use for this purpose. Again, saffron was known to both Egyptians and Greeks, and there is evidence of Egyptian use of the yellow colouring matter of safflower as a dye or stain for mummy cloths.
As a result of the discovery of Mexico and South America by the Spaniards at the end of the 15th century, many important dyes indigenous to those countries, as for instance, logwood, old fustic and the like, became available in Europe and provided the dyer with a range of effects formerly inaccessible. Kermes was soon replaced by the richer cochineal, and the employment of weld, young fustic and certain of the minor natural dyestuffs greatly decreased or was restricted to the production of special effects. (A. G. P.)