DYEING. 



China white, silver white, azure white, 

 or thread white. For this purpose a so- 

 lution of soap is prepared, the proper 

 strength of which is determined by its 

 mode of frothing when agitated; for the 

 China white, which should have a slight 

 tinge of red, a small quantity of anotta is 

 added, and the silk is shaken over in it 

 till it has acquired the desired shade. To 

 the other whites more or less of a blue 

 tinge is given, by adding a little blue to 

 the solution of soap. 



The preparation of silk with alum is 

 necessary in all cases, for without it the 

 greatest part of the colours applied 

 would possess neither beauty nor dura- 

 bility. For this operation forty or fifty 

 pounds of Roman alum, previously dis- 

 solved in warm water, is mixed with 

 about forty or fifty pails of water. 



After having washed and beetled the 

 silk, and wrung it out with the jack and 

 pin, in order to separate any soap it may 

 have retained, it is immersed in the 

 alum liquor for eight or nine hours, 

 after which it is wrung out by hand 

 over the vat, and washed in a stream of 

 water. 



The above quantity of liquor will be 

 sufficient for one hundred and fifty 

 pounds of silk; but when it grows weak, 

 which is known by the taste, twenty or 

 twenty-five pounds of alum, dissolved as 

 before, must be added, and this addition 

 must be repeated, till the liquor acquires 

 a disagreeable smell, and then it may be 

 employed for stuffs intended for browns, 

 roarones, and other dark colours, till it 

 has lost all its strength. The preparation 

 of silk with alum is always made in the 

 cold, because if the liquor should be em- 

 ployed hot, the lustre of the silk is liable 

 to be impaired. 



Of Cotton. 



The several species of cotton differ 

 principallyinthe length of their filaments, 

 their fineness, their strength and colour. 

 They are of different shades, from a deep 

 yellow to a white. The darkest cotton 

 comes from Siam and Bengal, and is of- 

 ten made into stuffs in its natural colour. 

 The most beautiful is not always the 

 whitest : it is necessary to bleach it. 

 Processes similar to those employed for 

 linen may be employed ; but those in 

 which oxygenated muriatic acid has been 

 used are more expeditious, produce a 

 more beautiful white, and prepare the 

 cotton better (according to M. Decroi- 



VOL. IV. 



sille) for the reception of a fine colour in 

 dyeing. 



In order to dispose cotton to receive 

 the dye, it must be first scoured ; some 

 boil it in sour water, but more frequently 

 alkaline ley is used ; the cotton must be 

 boiled in it for two hours, and then wrung 

 out, afterwards be rinsed in a stream of 

 water, till the water comes off" clear, and 

 then be dried. The cotton stuffs, which 

 are to be prepared, must be soaked for 

 some time in water, mixed with at most 

 one-fiftieth of sulphuric acid, after which 

 they must be carefully washed in a stream 

 of water and dried. The acid employed 

 in tins operation has been observed to 

 take up a quantity of calcareous earth 

 and iron, which would have injured the 

 colours. 



Aluming and galling are generally ne- 

 cessary in dyeing cotton and linen. 



In the preparation with alum, about 

 four ounces of it are required to each 

 pound of the stuff. It must be employ- 

 ed with the precautions mentioned in the 

 last article ; some add a solution of soda, 

 in the proportion of one sixteenth of the 

 alum, others a small quantity of tartar 

 and arsenic. The thread is well impreg- 

 nated by working it pound by pound in 

 this solution. It is then put altogether 

 into a vessel, and what remains of the 

 liquor is poured upon it. It is left there 

 for twenty-four hours, and then removed 

 to a stream of water, where it is suffered 

 to remain for an hour and a half, or two 

 hours, in order to extract a part of the 

 alum, and then it is washed. In this ope- 

 ration the cotton gains about one fortieth 

 of its weight 



In the operation of galling, different 

 quantities of galls, or other astringents, 

 are used, according to the quality of the 

 astringents, or the effect desired. The 

 galls, powdered, are boiled for about two 

 hours in a quantity of water proportioned 

 to that of the thread to be galled ; the li- 

 quor is then suffered to cool to a tempe- 

 rature which the hand can just support, 

 after which it is divided into a number of 

 equal parts, that the thread may be 

 wrought pound by pound, and what re- 

 mains is poured upon the whole toge- 

 ther, as described in the process of alum- 

 ing. It is then left for twenty-four hours, 

 especially when intended for maddering 

 for black, but for other colours twelve or 

 fifteen are sufficient. After this it is to 

 be wrung out and dried. When stuffs 

 are to be galled, which have already re- 

 ceived a colour, the operation must be 



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