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[106]  Annual Register 

Useful Projects. 

A Method of dying Wool and Silk, of a yellow colour, with Indigo; and also with several other blue and red colouring substances. Communicated to the Royal Society by Mr. Peter Woulfe; from the Philosophical Translations for the Year 1771. 

The Saxon blues have been known for some time; and are made by dissolving indigo in oil of vitriol, by which means the indigo becomes of a much more lively colour, and is extended to such a degree, that it will go very far in dying. 

A receipt for making the belt Saxon blue will, I dare say, be agreeable to many; I will, there-fore, give the following, which produces a very fine colour, and never fails of success. 

Mix 1 of the belt powdered indigo, with 4 of oil of vitriol in a glass body or matrass: and digest it for one hour with the heat of boiling water, shaking the mixture at different times; then add 2/3 12 of water to it, and stir the whole well, and when grown cold filter it. This produces a very rich deep colour; if a paler blue be required, it may be obtained by the addition of more water. The heat of boiling water is sufficient for this operation, and can never spoil the colour; whereas a sand heat, which is commonly used for this purpose, is often found to damage the colour, from its uncertain heat. 

Indigo, which has been digested with a large quantity of spirit of wine, and then dried, will produce a finer colour than the former, if treated in the same manner, with oil of vitriol. 

No one, that I know of, has heretofore made use of the acid of nitre, instead of the acid of vitriol; and it is by means of the former that the yellow colour is obtained: it was nevertheless natural to use it, on account of its known property of making yellow spots, when dropped on any coloured cloth. 

The acid of falt does not dissolve indigo, and therefore is of no use in dying. 

Receipt for making the Yellow Dye. 

Take 1/2 of powdered indigo, and mix it in a high glass vessel, with 2 of strong spirit of nitre, previously diluted with 8 of water; let the mixture stand for a week, and then digest it in a sand heat for an hour or more, and add 4 more of water to it; filter the solution, which will be of a fine yellow colour.

Strong

[107] For the Year 1772 

Strong spirit of nitre is liable to set fire to indigo; and it is on that account that it was diluted with water, as well as to hinder its frothing up. 2 1/2 of strong spirit of nitre will set fire to 1/2 of indigo; but, if it be highly concentrated, a less quantity will suffice. 

If the indigo be digested twenty-four hours after the spirit of nitre is poured on it, it will froth and boil over; but, after standing a week or less, it has not that property. 

One part of the solution of indigo in the acid of nitre, mixed with four or five parts of water, will dye silk or cloth of the palest yellow colour, or of any shade to the deepest, and that by letting them boil more or less in the colour. The addition of alum is useful, as it makes the colour more lasting; according as the solution boils away, more water must be added. 

None of the colour in the operation separates from the water, but what adheres to the silk or cloth; of consequence this colour goes far in dying. 

Cochineal, Dutch litmus, orchel, cudbear, and many other colouring substances treated in this manner, will all dye silk and wool of a yellow colour. 

The indigo which remains undissolved in making Saxon blue, and collected by filtration, if digested with spirit of nitre, dyes silk and wool of all shades of brown inclining to a yellow. 

Cloth and silk may be dyed green with indigo; but they must first be boiled in the yellow dye, and then in the blue. 

Method of making solid and comby Pot-ash. 

There are very considerable quantities of foreign ashes, imported into this kingdom from Russia, Spain, &c. 

But we have only two kinds of ashes made in our country, viz. Solid, or hard, and comby, or light ashes, and both in demand for home consumption. 

The subjects, of which the different kinds are made, are as follow. 

Wood-ahes, which are principally made in farm houses, &c. where wood is burnt as fuel, are bought up by the pot-ash burners, from six-pence to eight-pence, and sometimes ten-pence, per bushel, corn measure *, and carried to the pot-ash office, in which are erected large fats, or vats, (containing from four to eight score bushels of wood-ashes) with under-becks, and are wrought by threes; so that there are either three, six, or nine vats in every office, and for this reason: 

The ashes being trod down into the vats, a sufficient quantity of water is continued to be laid on till it runs through the ashes into the under beck. The liquor  running from the first is laid on the second vat, which is one third stronger than the first; and the liquor of the second vat is laid on the third, which is also one third stronger than the second. When it has thus run through the third vat, the lees, as the liquor is then called, is supposed to be strong enough for burning; but the strength is proved by weighing the lees in small quantities. 

*Wood-ashes in Essex are bough up for this purpose from five-pence to seven-pence per bushel. 

Transcription Notes:
---------- Reopened for Editing 2023-05-12 11:40:56 There are symbols I was not familiar with preceding most of the numbers for the measurements.