or wood is to be added. When the wool or cloth is to be put into the indigo vat to be dyed, it should be wrung out of tepid water, and then introduced into the vat, where it should be kept for a longer or shorter time according to the strength of shade required. After being taken out, it is exposed to air, when the green colour which it had imbibed in the vat is changed to a blue by the absorption of the oxygen of the atmosphere. It is then to be carefully washed.

Woad itself contains a colouring matter exactly similar to indigo, and indigo may be extracted from it, but the quantity is small.

Cotton and linen are dyed blue by putting the indigo into a solution of some substance that has a stronger affinity for oxygen than the green bases of indigo. Green sulphate of iron, and metallic sulphurets answer this purpose, the green sulphate attracts the oxygen from the indigo, and reduces it to the green state, in which it is dissolved by lime added to the solution. The cloth is then put into the bath.

Silk is dyed blue by indigo fermented by bran and madder, and the indigo dissolved by potash. If the shade required be dark, it is dyed first with archill, which is called giving it a ground colour.n

Of dyeing Black.

The substance that produces the black dye is the tanno-gallate of iron. Decoctions of many vege

tables strike a black with a solution of the red oxide of iron. Of these nut-galls give the most copious precipitate.

Logwood is generally employed as an auxiliary, because it communicates lustre, and adds consider

ably to the fullness of the black.

The decoction of logwood which is reddish becomes black by sulphate of iron.

To dye cloth or wool black, the first process generally is to dye it blue, which renders the black to be given more intense. If the cloth be coarse, and the blue dye too expensive, a brown dye may be given by means of walnut peels. It is then boiled for two hours in a decoction of nut galls, and then for two hours more in a bath composed of logwood and sulphate of iron, at a scalding heat, but not boiled. During the operation, it must be frequently exposed to the air. The common proportion are five parts of galls, five of sulphate of iron, and thirty of logwood, for every 100 of cloth. For coarse cloths the previous blue dye is omitted. The cloth is then washed and fulled.

Silk is dyed black as follows. After boiling it with soap, it is galled, and afterwards washed. It combines with a considerable portion of the astringent principle, and increases in weight. It is then dipped into a bath of sulphate of iron and gum arabic.

Cotton and linen are first dyed blue, then steeped in a decoction of galls, and alder bark. It is then put into a bath of acetite of iron, taken out and exposed to the air. This operation is repeated

several times.

Of dyeing Compound Colours.

Compound colours are produced either by mixing together two or more simple ones, or by dyeing cloth first one simple colour and afterwards

another.

Wool

Greens are formed of blues and yellows. is dyed green by dyeing it first blue of a depth of shade sufficient for the required kind of green. It is then washed and boiled in a bath of weld and tartar, or any of the processes used for dyeing blue and yellow may be used. Various shades will be given by different proportions of the dyeing materials. The green called Saxon green is obtained by solutions of indigo in sulphuric acid, sometimes quercitron bark is used. Another process for Saxon green is by the quercitron bark, and then a bath of the murio-sulphate of tin and alum with sulphate of indigo.

Purples, violets, &c.-All the shades of these colours are formed of blue and red. Sometimes the cloth is dyed blue and then scarlet, and sometimes cochineal is mixed with sulphate of indigo, and the purple dyed at once. Silk is dyed first by cochineal and afterwards by indigo. Cotton and linen are dyed blue, then galled, and boiled in logwood.

Orange colours are produced by mixtures of yellow and red. Wool is first dyed scarlet and then yellow.

Olive is blue combined with red and yellow. Cinnamon colour is given to wool by dyeing it first with madder, then yellow. Silk is dyed the same colour by logwood, Brazil-wood, and fustic. Cotton and linen receive a cinnamon colour by weld and madder.

Brown is given to cloth by quercitrón bark, or by walnut peels.

When walnut peels, or the green covering of the walnut, are first separated, they are white internally, but soon assume a brown or even a black colour on exposure to the air. They readily give up their

colouring matter to water. It is common to keep them in water for a year before they are used. Wool is dyed brown with them by steeping in a decoction for a length of time proportioned to the depth of colour required. The same colouring matter is found in the root of the walnut-tree, but in smaller quantity. Other trees, as the bark of the birch may be used for dyeing browns, and in these cases it is probable that the colouring matter is combined with the tanning principle, and this may be the reason why no mordant is necessary, both the cloth and colouring matter having a strong affinity for tannin.

Drab colours are dyed by combining brown oxide of iron with the cloth, and then the yellow of quercitron bark. The strength of shade will be more or less, by varying the quantity of the mordant, when the proportion is small the colour inclines to olive or yellow, on the contrary the drab may be deepened or saddened, as the dyers term it, by mixing a little sumach with the bark.

CALICO PRINTING.

2

Calico is a species of cotton cloth ornamented with coloured patterns. The name is derived from Calicut, a district of India, where it was first made, and from whence it was formerly imported. The art of making calicoes had been practised there from time immemorial, but it is scarcely a hundred years since it was known in Europe; it has already risen to such perfection as to equal if not exceed the manufactures of India, in the elegance of the patterns, the beauty and permanance of the colours, and the expedition with which the different operations are carried on.

The process of calico-printing consists in impregnating those parts of the cloth which are to receive the coloured pattern with a mordant, and then dyeing the cloth by the usual methods. The dye is firmly fixed to that part only where the mordant has been applied; and, although the whole cloth has received the tint, yet the colour will be easily discharged from the unmordanted parts by washing, and exposing on the grass to the sun and air for some days with the wrong side uppermost. Thus, suppose a pattern had been applied to white cloth with a solution of acetite of alumine, and that then the whole was dyed with madder; when taken out of the dye-vat the whole cloth would be red; but, by washing and bleaching, the madder will be discharged from every part of the cloth except where the acetite of alumine had been applied; and, consequently, the pattern alone will appear red. In the same manner the patterns may be applied of any other colour by varying the dye, as quercitron bark or weld for yellow, &c.

Two mordants are particularly employed in calico-printing, acetite of alumine, and iron dissolved in some vegetable acid.

The acetite of alumine is made by a double decomposition of alum and sugar of lead. When iron is used as a mordant, it is dissolved in vinegar, soured beer, or pyroligneous acid; and it is, therefore, an acetite of iron mixed with a portion of tartrite, gallate, and, perhaps, other salts of the metal.

When the colour of the required pattern varies in different places, this effect is produced on the cloth, by impregnating the several parts with various mordants. Thus, if one part is printed with acetite of alumine, and another with acetite of iron,