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To discharge colours

The dyers generally put all coloured silks which are to be discharged, into a copper in which half a pound or a pound of white soap has been dissolved. They are then boiled off, and when the copper begins to be too full of colour, the silks are taken out and rinsed in warm water. In the interim a fresh solution of soap is to be added to the copper, and then proceed as before till all the colour is discharged. For those colours that are wanted to be effectually discharged, such as greys, cinnamons, &c. when soap will not do, tartar must be used. For slate colours, greenish drabs, olive drabs, &c. oil of vitriol in warm water must be used; if other colours, roche alum must be boiled in the copper, then cooled down and the silks entered and boiled off, recollecting to rinse them before they are again dyed. A small quantity of muriatic acid, diluted in warm water, must be used to discharge some fast colours; the goods must be afterwards well rinsed in warm and cold water to prevent any injury to the stalk.

To discharge cinnamons, greys, &c. when dyed too full. Take some tartar, pounded in a mortar, sift it into a bucket, then pour over it some boiling water. The silks, &c. may then be run through the clearest of this liquor, which will discharge the colour; but if the dye does not take on again evenly, more tartar may be added, and the goods run through as before. To re-dye or change the colours of garments, &c.

The change of colour depends upon the ingredients with which the garments have been dyed. Sometimes when these have been well cleaned, more dying stuff must be added, which will afford the colour intended; and sometimes the colour already on the cloth must be discharged and the articles re-dyed. Every colour in nature will dye black, whether blue, yellow, red or brown, and black will always dye black again. All colours will take the same colour again which they already possess; and blues can be made green or black: green may be brown, and brown green, and every colour on re-dyeing will take a darker tint than that at first.

Yellows, browns, and blues, are not easily discharged; maroons, reds, of some kinds, olives, &c. may be discharged.

For maroons, a small quantity of roche alum may be boiled in a copper, and when it is dissolved, put in the goods, keep them boiling, and probably, in a few minutes, enough of it will be discharged to take the colour intended. Olives, greys, &c. are discharged by putting in two or three table spoonfuls, more or less, of oil of vitriol: then put in the garment, &c. and boil, and it will become white. If chemic green, either alum, pearl-ash, or soap, will discharge it off to the yellow; this yellow may mostly be boiled off with soap, if it has received a preparation for taking the chemic blue. Muriatic acid used at a hand heat will discharge most colours. A black may be dyed a maroon, claret, green or a dark brown; and it often happens that black is dyed claret, green, or dark brown; but green is the principal colour into which black is changed.