[ 175 ] 188 



They may be worked in this batii, adding a little azure lu ii, ii iie- 

 eessary. When they are at the proper point, they arc to be well 

 washed in the river, which gives them the firmness they had lost in 

 the soap water; afterwards they are to be wrung and sulphured. 



The fine Nankin or China silks, which are naturally of a very fine 

 white, are in no need of this operation. " 



We owe to Beaume the discovery of a process by which the natu- 

 ral stiffness of the silk is preserved, while it is rendered perfectly 

 similar to that of China, with which they manufacture gauzes, blond 

 lace, ribbons, &c. 



This process consists in digesting, for twelve hours, six pounds of 

 silk, in a mixture of forty-eight pounds of alcohol, at thirty degrees, 

 and 12 ounces of muriatic acid, at fifteen degrees of concentration. 



This liquor is poured off when it has become slightly colored, and 

 replaced with alcohol, which we pour over the silk until no more co- 

 loring matter passes off with it. It is then covered with a similar mix- 

 ture of alcohol and acid, as at first, which is allowed to stand on it 

 two or three days, or until the silk be perfectly white. It is then 

 freed from any remains of the acid and alcohol, by washing it in cold 

 water. 



The silk bleached by this method and loosely dried, is without lus- 

 tre. It ought to be strongly extended while dripping wet. and left to 

 dry in this state of extension.! ' 



Of JiluTning. 



After having washed the silks, and divested them of the soap by 

 giving them a beetling, a line or cord is passed through them, as when 

 they are put to boil. They are put into the alum, all strung together, 

 taking care that the hanks be not too much rolled up, or folded upon 

 one another, and that the bundles, (cordees,) be not too much in the 

 air, or at the surface, so that the whole may be well steeped. They 

 are to be left in this state during eight or nine hours, commonly from 

 night till morning, J afterwards they are to be washed and wrung with 

 the hand, over the vessel : they are then carried back to the river to be 

 washed, which is called refreshing; and beetled when necessary. 



The proportion of alum to be used, for a cask or tub of forty or fifty 

 buckets full, is forty or fifty pounds, which should be first dissolved in 

 a kettle of hot water; care must be taken, in pouring the solution of 

 alum into the tub, to stir up and mix it, because the coldness of the 

 water might produce a crystallization or congelation, as diers term it. 

 We may put into such a bath about one hundred and fifty pounds of 

 silk, without being under the necessity of adding more alum; but 

 when we perceive that it begins to be weak, then there must be twenty 

 or twenty-five pounds of alum dissolved in it, with the same precau- 



* Baillot, p. 98. 



I Chemistry applied to the Arts, by Chaptal, p. 422. Paris, 1807 



-. Adifrsays tliat four hours of the alum .steepine: is enou.erh 



