The Dyer's Guide / Being a compendium of the art of dyeing linen, cotton, silk, wool, muslin, dresses, furniture, &c. &c.; with the method of scouring wool, bleaching cotton, &c., and directions for ungumming silk, and for whitening and sulphuring silk and wool; and also an introductory epitome of the leading facts in chemistry, as connected with the art of dyeing

by Thomas Packer

To prepare the indigo mentioned in the preceding directions.

Boil, in a gallon of water, for three quarters of an hour, two ounces of pot-ash, three quarters of an ounce of madder, and one ounce of bran; then let the whole settle for half an hour. After all is settled and taken out of the boiler, and put into another copper with four ounces of indigo finely powdered, the liquor should be kept stirred, and very hot, but not be boiled. At intervals some lixivium of lime should be put into it, and that being cold will keep the liquor from boiling, and render the pot-ash more active.

As soon as the indigo is dissolved and properly diluted, damp the fire and cover over the solution; after it is settled put in a pattern, which, when taken out, will turn blue on being exposed to the air; if it does not, more clear lixivium must be added. Of this solution of indigo such proportions are to be added to the woad vat as are directed in the preceding process.

Rules to judge of the state of the woad vat.

The vat is ready for working, and to dye blue, when the sediment at the bottom, on being taken out of the vat changes to a fine brown-green. When the froth which rises in great bubbles on the surface is of a fine Prussian-blue, and when the pattern which has been steeped an hour, comes out of a dark grass-green, and changes in the air to a blue; when the liquor is clear and reddish, and the drops which stick to the rake are brown; when the sediment changes colour on being taken out of the liquor, and becomes brown on exposure to the open air: when the liquor is neither harsh nor greasy to the feel, and neither smells of lime nor of ley, the vat is known to be in a proper state for working.

Indications when a vat has had too much or too little lime.

These extremes ought to be carefully avoided. When the lime is deficient, or a pattern comes out of a dirty grey, and the sediment does not change its colour, there is scarcely any effervescence on the vat; the liquor smells only of lime, or of the lixivium of lime.

To remedy the deficiency of lime.

If the vat be not too far gone, after the addition of a little bran, madder, and some woad, then try the patterns from hour to hour; thus you will be enabled to judge.

A deficiency of lime is evident when there is no effervescence on the liquor; and when, by dashing about the surface of the liquor, it makes a hissing noise, and by the bursting of a number of small air bubbles, which as soon as they are formed break, and appear tarnished, and are not large, nor of a fine colour; the liquor too has an offensive smell, like rotten eggs; it is harsh and dry to the feel, and the sediment, as has been before observed, does not change colour when taken out of the liquor.