In the preparation of the dyeing bath from twelve to eighteen pounds of quer citron bark are inslosed in a bag, for every hundred pounds of the stuff, vary ing the proportion according to the shade required. The bark is put into the water while cold, and immediately after the stuff is immersed, and agitated or turned in it for an hour or an hour and a half; during which the water should be gra dually heated, and the temperature rais ed to 120°. At the end of this time the heat is increased, and the dyeing liquor brought.to a boiling temperature ; but at this temperature the stuff must only remain in it for a few minutes, because otherwise the yellow assumes a brownish hue. The stuff, having thus acquired a sufficient colour, is taken out, rinsed, and dried.
Many attempts have been made to imi tate the shade of yellow which nankeens possess ; but none have hitherto succeed ed, so as to produce a colour whose dif ference from the real nankeen could not be in general distinguished at first sight ; or in the very few instances where this was at all doubtful, a little wear soon be trayed this deception. Chaptal has recom. mended a colour procured from salt of iron for this purpose; and in the processes of others, iron in general has been the co louring substance used ; but a colour from iron has the evident defect of get ting black stains from the least touch of any astringent liquor, to which it is per petually liable wherever' tea is used. It is therefore useless to insert receipts for a colour which never yet came suffi ciently near what it was intended, to pro duce the least competition in the market with the real article.
Nankeen is made of cotton, whose co lour is naturally such as we see it ; some of the best grows in Bhaugalpore in the East Indies ; it would be an object well worth the attention of tilt cotton plant ers in the West India Isands, to get over plants or seeds of this species of cotton, to raise it for the English market. Per haps the Bhaugalpore cotton might be imported from the East cheap enough for the use of our manufacturers, which would save the nation much of the large sums that go out of it annually for the purchase of nankeens.
Of dyeing Wool green.
Having given an account of the most approved processes for dyeing the four simple colours, black, red, blue and yel low, we now proceed to the compound co lours ; which are so called, because in ge neral they are produced in dyeing by mix tures of the simple colours, though in a kw instances substances are found which produce some of the compound colours without addition.
To dye woollen green, either a blue or a yellow dye may be first given to it ; hut the first is generally done, because the yellow dye of the stuff would injure the blue bath. The intensity of the blue must be proportioned to the shade of green required. When the blue dye is given, the yellow is communicated by some of the processes described. The cloth, having first got the proper ground, is washed at the fulling mill, and boiled as for the common process of weld ing; but when the shade is to he light, the proportion of salts should be less. In this case the quantity of weld used should also be less, but for all other shades it should be greater than for dyeing simple yellow.
Sulphate of indigo is employed for the greens called Saxon greens. Dr. Ban croft directs for this dye, that from six to eight pounds of quercitron bark, en closed in a bag, should he put into the bath for every hundred pounds of cloth, with only a small proportion of water just as it begins to grow warm. When the water boils, six pounds of murio sulphate of tin should he put in, and a few minutes after, about four pounds of alum ; these having boiled five or six minutes, cold water should be added, and the fire be diminished, so as to bring down the heat of the liquor nearly to what the hand is just able to bear ; im mediately after this as much sulphate of indigo is to be added, as will suffice to produce the shade of green required, taking care to mix it thoroughly with the bath. The cloth, previously scoured and moistened, should then be expeditiously put into the liquor, and turned very brisk. ly through it for a quarter of an hour, that the colour may apply itself evenly in every part. By these means very full, even, and beautiful greens may be dyed in half an hour ; but during this space it is best to keep the liquor a little below the boiling heat.
Of dyeing of Silk green.
The silk is first scoured, as for other colours ; and for light shades the scour ing must be as complete as for blue. It is then first dyed yellow in small parcels, (after being well aimed, and slightly washed at the river) by carefully turning it in the weld bath. When it has ac quired the proper shade of yellow for t green required, which is known by t ing a pattern in the blue vat, it is tak out, washed, and then immersed in tl blue vat. A deeper colour is given, a the shade varied, by adding a decoc Lion of logwood, fustic, or anotta, to th yellow bath, after the weld has bee taken out. For light shades a lighte ground is given.