ON COLOllING. 63 



rope such vats have been kept for ages, being replenished from 

 time to time by additions of the several ingredients above men- 

 tioned. By repeated dippings in black dyes, silk may be made 

 to acquire nearly a fourth part more in weight than it possessed 

 before its natural gum had been separated from it by the boiling 

 with soap, a [)rocess to which all new silk should be subjected 

 before it it is colored. But the color produced by this excess of 

 black is not so good as it is when no such excess has been em- 

 ployed. As soon, therefore, as the silk becomes sufficiently 

 colored, judging by the eye, it should be rinsed out and passed 

 through a bath containing at the rate of one pound of starch and 

 half a pound of linseed oil, well mixed with six quarts of warm 

 water. 



BLACK, ON COTTON. 



Cotton may he colored black in the dyes above mentioned for 

 wool and silk. A somewhat different management is however 

 recommended by the best writers on the subject. One, who is 

 considered good authority, recommends making a decoction by 

 boiling the logwood, maple bark, &c. above directed, and pour 

 the clear liquor into a tub. Fill another tub with a like quantity 

 of lime water, and another with the copperas water, formed by 

 dissolving two and a half ounces of copperas to each gallon of 

 water, and while the decoction and lime water are nearly boiling 

 hot, dip and turn the cloth for thirty minutes, take it out, wring 

 and air it ; then put it into the copperas water and turn it as 

 usual fifteen minutes, wring and air it again, then dip it in the 

 lime water five minutes, and let it be well washed. If the color 

 does not become sufficiently dense, repeat the operations until 

 the desired effect be obtained. Then dip it in the mixture of 

 starch, oil and water, as directed for silk. Much benefit may 

 also be expected from soaking it a short time, previous to its 

 being oiled, in a mixture of ox gall and water. When the cloth 

 has not been first dyed blue with indigo, more dippings and a 

 stronger decoction of logwood will be necessary. In some great 

 dying establishments the black vat, as directed above, is chiefly 

 used for coloring cotton black, instead of the copperas water, and 



