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SECT. VIII.

Of the dying of silk black .

R AW silk, in the state in which it is wound oftfrom the cocons, has a harshness which renders itunfit for being spun, and for the most part a pretty deepyellowish or reddisli-yellow colour, from both which itis cleansed, by boiling it with soap, and afterwardsthoroughly washing it with soft water : when woven, itis again washed with soap, to free it from the greasinessit may have contracted, which would occasion it to bespotted in dying. The silk loses in the boiling generallyabout a fourth part of its weight: this proportion isassigned by the writers on dying, and on enquiry amongthe workmen, I find it universally allowed to be the near-est calculation. In being dyed black, this loss is fullymade up, the weight of the dyed silk being commonlyeven greater than that of the raw silk. There is no dyewhich adds so much to the weight as black : the increaseis considerable in woollen as well as in silk, though mosttaken notice of in the latter on account of its great price.

Mr. Macquer observes, in his art de la teinture en fie,published in 1763, that the finest oil soap is required forthis cleansing of silk; that there is nothing saved by using-the inferior kinds, a proportionably greater quantity ofthem being necessary; that some sorts of soap curdlewith the matter which they extract from the silk, into asubstance almost of the consistence of wax ; that those,which are made with animal fats, prevent the silk fromhaving the proper dryness and lustre, and dispose it togrow reddish in keeping; that even the best soaps areaccompanied with some imperfections in this respect, and-that the superiority in lustre, of the Chinese silks to the

European,,