The above proportion of alum will do for a hundred and fifty pounds of silk, before you need replenish it; when this is necessary add twenty-five pounds more of alum, as at first directed in Chapter III., and so continue to replenish it till it gets a bad smell. When this is the case you may dip for browns, maroons, &c.; and afterwards throw the liquor away; the trough is then to be rinsed for a fresh liquor.
Remember always to alum cold or you will spoil the lustre of the silk.
Skein silk for YELLOW.
This is to be boiled with about twenty pounds of soap for every hundred pounds of silk. When boiled it is to be washed and alumed, and again washed, dressed, and put on the rod, seven or eight ounces to a rod, and then dipped and re-turned in the yellow liquor, in the proportion of two pounds of weld to one pound of silk.
The liquor is not to be hotter than the hand can bear while the silk is in it. The silk, when in the vessel for dyeing, should cause the liquor to float within two inches of the edge. The silk must be taken out and the liquor strengthened, if the pattern is to be very full; when full enough, one pound of pearl-ash for every twenty pounds of silk must be dissolved in some warm water; about a quarter of this liquor is put into the dye bath: take the silk out while you put in the liquor, stir the mixture well. Put in the silk and work it, turning and re-turning it as at first. After seven or eight re-turns, one of the hanks is to be taken out, wrung, and tried at the peg, and, if sufficiently full and bright, all is well; if not enough so, some more pearl-ash liquor must be added, and the silk worked as before, till the shade required is obtained.
For jonquil it may be necessary to add some annatto when you put in the pearl-ash.
To make the light shades, such as canary or lemon, perfectly white, they must be boiled with thirty pounds of soap to a hundred of silk; and if these be not azured to be dyed, they must have a little of the blue vat, and a little of the weld liquor in water, (the whole mixture being as hot, but no hotter than the hand will bear,) and the silk ready on rods, must be quickly worked through and out. For deeper lemons the same process must be used as for the fuller yellows; only less weld, and twenty pounds of soap will do for a hundred pounds of silk in whitening it.
The blue of the vat is only used for such articles as are to have a green cast, and that extremely light; the aluming also should be in a weaker alum liquor: for light lemons it should be prepared in a separate liquor.
Preparation of annatto for AURORA, ORANGE, MOIDORE, GOLD COLOUR and CHAMOIS.
You must have a colander proportioned to the size of the copper in which you boil the annatto. To every pound of annatto put from twelve ounces to one pound of pearl-ashes, which last dissolve in water, and add the solution, by degrees, to the solution of annatto as it boils and dissolves, for which purpose the annatto must be suspended in the colander over the copper by a flat stick about six inches broad, run through a flat handle on each side of the colander, by which means the colander is kept sunk in the water with the annatto in it, till it is all dissolved, except some little foreign matters. The holes in the colander should be moderately small.