62 ON COLORING. 



water for one hour. Take out the bark, immerse the cloth, and 

 boil another hour. Then take 5 ounces of copperas, dissolved 

 in 29 lbs. of water, and add it slowly to the liquor in the boiler. 

 The cloth should be kept continually turning in the boiling 

 liquor for two hours. Take it out, cool it, and again soak it in 

 boiling water, to which a small quantity of ox gall or fresh cow 

 dung has been added, another hour. Rinse it out and scour it 

 well with hot water and hard soap. 



Cloths not colored with indigo, will take a good black if the 

 quantity of logwood be increased, and the dippings alternately 

 in the decoction of the bark, he. be many times repeated. 



BLACK, ON SILK. 



The fibres of silk do not so readily receive the black dye as 

 those of wool. What the woollen dyer effects by three or 

 four dippings, the silk dyer scarcely obtains from twenty. As 

 the affinity of the silk for the soluble part of the galls or maple 

 bark is greater than with the iron, it is thought most advanta- 

 geous to begin by boiling about one half as much in weight of 

 the galls or bark as of the silk to be dyed, in a suitable quantity 

 of water, for three or four hours. Let it settle, pour off the 

 clear liquor, and macerate the silk in the same for twenty four 

 hours. Being dried and slightly rinsed, the silk is afterwards 

 immerssd in a solution of the sulphate of iron (copperas), mod- 

 erately warmed, and kept therein twelve hours, after which it 

 should be rinsed and immersed in a warm decoction of log- 

 wood for several hours, again immersed in the solution of iron, 

 rinsed, again transferred to the decoction of bark, he, repeating 

 these alternate immersions till the desired color shall have been 

 produced. Iron, dissolved in vinegar, is still better than cop- 

 peras. A black vat may be easily prepared for coloring silk, by 

 immersing in vinegar old iron hoops, turnings of iron, or iron 

 in small and thin pieces, to which may be added maple bark, 

 the berries and bark of the sumach, oak bark, alder bark, &c., 

 and left to undergo a gradual solution, by the joint action of 

 the acids and acerb vegetable matters. The longer the liquors 

 are kept, the better. In some coloring establishments in Eu- 



