Sumach is the production of the rhus coriaria, a shrub which grows naturally in Syria, Palestine, Spain, and Portugal. It is cultivated in the two last countries with great care. Its shoots are cut down every year quite to the root, and after being dried are reduced to powder, and thus prepared for the purposes of dyeing, &c. Sumach bears a great resemblance, as an astringent, to galls. Sumach alone gives a brown and a fawn colour, but cotton stuffs impregnated with acetate of alumina take a durable yellow from it.
Tartar, see Argol.
Tin, dissolved in nitric or muriatic acid, forms solutions of great importance in many processes of dyeing, particularly scarlet. These solutions are called respectively nitrate and muriate of tin.
Turmeric is a root obtained from a plant growing both in the East and West Indies. The root is used chiefly for dyeing yellow; but it is a fugacious colour.
Verdigris is a crude acetate of copper, obtained by exposing copper plates to the husks, &c. of grapes, which containing considerable acetic acid, the acid combines with the surface of the copper plates, forming a blueish green rust, which is scraped off, and forms the verdigris of commerce. A still more complete acetate of copper is obtained in distilled verdigris, which is in elegant green crystals. The best verdigris is made in France; some is now also made in this country.
Weld, sometimes called improperly Woulds, dyer's-weed, or Reseda luteola, is a plant found wild, in this country, but cultivated for the purposes of the dyer; it is much used for yellows.
Woad, or Pastel, is obtained from a plant growing in various parts of Europe and also in this country; it is the Isatis tinctoria, and is cultivated with care for the dyeing matter which it affords, and which is obtained from the leaves of the plant, collected and prepared in a particular manner. Woad gives a full-bodied and fast blue to wool, yet not very bright, so that it is usually mixed with indigo[3].
Besides the preceding substances we may mention that annatto is used for dyeing several colours; kermes, madder, and Brazil wood for reds; logwood for purple and black; peach-wood for maroon, &c.; fustic, dyer's-broom, saw-wort, French-berries, &c. for yellow; walnut-root, and the outside green shell of the nuts for browns. We may also mention prussiate of potash, acetate of lead, commonly called sugar of lead, and oxide of manganese, as occasional articles used for various purposes by the dyer. Several other substances are also used in dyeing, which we cannot enumerate; some are mentioned in the subsequent pages. We may, however, name cam-wood, bar-wood, redsanders, and myrobolans. We ought also to observe that how desirable soever it may be to have all woods for dyeing, in powder, in order to obtain the greatest quantity of colouring matter from them by decoction or otherwise, yet, as in a powdered state they are much more likely to be adulterated than in chips, it is most advisable to purchase them in this last state; logwood in particular ought never to be purchased in powder.
On the Component Parts of Vegetable and Animal substances.
In order more correctly to understand the theory and practice of dyeing, it is essential that the pupil should become acquainted with the nature of the substances upon which and with which he must necessarily operate. We shall not enter into the theories of light and of colours, as propounded by Sir Isaac Newton, as well as many illustrious chemists, who have already done so much for the art of dyeing, but shall simply refer to such writers as Ure, Bancroft, Berthollet, Brande, &c. from whom may be learnt what is of most importance to be known concerning this curious subject.