DYEING. 



the bottom, And an hour is allowed for 

 dissolving the gum, which is occasionally 

 stirred. If all the gum be dissolved in 

 that time, three or four pounds more 

 may be added. The cullender is only re- 

 moved during the dyeing, and is put in 

 again after it : the copper is kept hot the 

 whole time, but not suffered to boil: the 

 silk is gulled with one-third of Aleppo 

 galls, and left in the liquor six hours the 

 first time, and twelve the second. The 

 rest of the process is conducted in the 

 common method. The gum is useful to 

 keep the dye suspended in the liquor ; 

 but it is probable a smaller quantity might 

 answer 



As galls are expensive, the following 

 method has been used to lessen their con- 

 sumption. The silk, after being boiled 

 and washed in the river, is prepared by 

 immersing it in a strong decoction of 

 walnut peels till the colour is exhausted : 

 it is then wrung, dried, and again washed 

 in the river ; after which it is left in a so- 

 lution of two ounces of verdigrise for eve- 

 ry pound of silk, in cold water, for two 

 hours, and then dipped in a strong decoc- 

 tion of logwood, which gives it a blue 

 ground ; it is then wrung out, dried, and 

 washed in the river. The black bath for 

 it is prepared by macerating two pounds 

 of galls and three of sumach in twenty- 

 five gallons of water, over a slow fire, 

 for twelve hours ; after straining, three 

 pounds of sulphate of iron and as much 

 gum arabic are dissolved in it. In this 

 solution the silk is dipped at two different 

 times, left two hours in the bath each 

 time, and aired and dried after each dip- 

 ping ; it is then beetled twice at the river, 

 dipped again, and left in the bath four or 

 five hours; drained, dried, and again 

 beetled twice, as before. The heat of the 

 bath must not exceed 122 Fahrenheit. 

 Before each of the last clippings, half a 

 pound of sulphate of iron, awl as much 

 gum arabic, should be added. Some 

 think that the galls are only added to 

 increase the weight, and that the sumach 

 is sufficient for the dye. 



Of dyeing Cotton and Linen black. 



Cotton and linen do not take a black 

 that will resist soap. The weakness of 

 their affinity for iron renders a 'solution 

 of it necessary in dyeing them in some 

 acid, to which it has less attraction than 

 to the sulphuric. This solution is pre- 



Sared with iron and vinegar, or alegar 

 'om small beer or fermented worts, ac- 

 cording as the country where the process 



it carried on affords them cheapest. (Py- 

 rolignous acid, or the acid liquor pro- 

 cured in distilling spirits of turpentine, 

 has also been used for the same purpose 

 with success.) Pieces of old iron are 

 thrown into the acid liquor, and they 

 are allowed to remain in it six weeks 

 or two months before it is used, that it 

 may be fully saturated with the iron. 

 This solution is called iron liquor in this 

 country. 



The process for dyeing linen and cot- 

 ton thread black at Rouen is the follow- 

 ing. It is first dyed sky blue ; then wrung 

 out and dried, (a deep blue is thought to 

 be better;) it is next galled, using four 

 ounces of galls to every pound of thread, 

 and leaving them twenty -four hours in 

 the gall liquor: after which they are 

 wrung out and dried again. About five 

 quarts of the iron liquor are then poured 

 into a tub, in which the thread is worked 

 by hand, pound by pound, for a quarter 

 of an hour, and then wrung out and 

 aired. This operation is repeated twice, 

 adding each time a fresh quantity of 

 the iron liquor, which should be care- 

 fully scummed; after this the thread is 

 again aired, wrung out, washed at the 

 river, and dried. 



The thread receives the colour by im- 

 mersion in the following bath. A pound 

 of alder bark for every pound of thread 

 is boiled an hour, in a sufficient quantity 

 of water; about half the bath that served 

 for the galling, and half as much sumach 

 as alder bark, are then added, and the 

 whole boiled together for two hours, and 

 strained through a sieve. When the li- 

 quor is cold, the thread is put into it on, 

 sticks, and worked pound by pound, air- 

 ing it from time to time ; it is then let 

 down into the bath again, left in it twenty- 

 four hours, wrung out, and dried. To 

 soften this thread, it is usual to soak and 

 work it in the remains of a weld bath, that 

 has been used for other colours, adding 

 to it a little logwood. 



At Manchester, the method used is, to 

 first gall the stuff with galls or sumach, 

 then to dye it in the iron liquor, and af- 

 terwards to dip it in a decoction of log- 

 wood and a little verdigrise. This process 

 is repeated till a deep black is obtained. 

 It is necessary to wash and dry after each 

 operation. The iron liquor for this pro- 

 cess is frequently composed of infusion of 

 alder-bark and iron. 



M. Guhliche recommends highly the 

 following solution of iron for dyeing linen 

 and cotton. A pound of rice is to be 





