The Dyer's Guide. Chapter IV. On Scouring and Dyeing Wool. On the action of alum and tartar upon wool.

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.
Directions for Ungumming Silk, And For Whitening And Sulphuring Silk And Wool.
And Also
An Inttroductory Epitome of The Leading Facts in Chemistry, As Connected With The Art of Dyeing.

By Thomas Packer,
Dyer and Practical Chemist.

"Cet arte est un des plus utiles et des plus merveilleux qu'on connoisse."
- Chaptal.

"There is no art which depends so much on chemistry as dyeing."
- Garnett.

Second Edition,
Corrected and Materially Improved.

Printed for Sherwood, Gilbert, And Piper,

Wool is usually scoured for being dyed with stale urine, the staler the better; it is used in the proportion of one part to three parts of water, full as hot as the hands can bear when the wool is worked about in the fluid. — If the wool be in the fleece, what is called its natural yolk, and which is said to preserve the wool from the moth, is of a greasy nature, and is scoured out by the volatile alkali in the urine. If the wool be in the state of spun yarn it has gallipoli, or rape oil, in its thread, the spinner, or rather the comber, using it to render the wool more flexible, &c. It is absolutely necessary that wool, (as indeed every other material to be dyed) should be made very clean and white, if any brilliant or bright colour is to be imparted to it. For this reason it is that the wool is passed two, three^ and in some instances even four times through fresh scouring liquors; in the last, and sometimes in that which precedes the last, soap is used in the proportion of from seven to fourteen pounds, and in some instances to twenty one pounds or more, to a pack of two hundred and forty pounds of wool, according as it is fine or coarse: for superfine colours more than common is used. Worsted requires less than coarse yarn, having less grease and dirt in it.

It ought, however, to be known, that boiling wool for a long time in any alkaline liquors, or a liquor made of soap, tends greatly to the decomposition of the cloth; indeed long boiling in any strong alkaline ley converts wool into a kind of soap, and, hence, it is easy to see why such processes injure wool or cloths made with it.

The preceding observations apply to the alkalies in a caustic state, or in the state of carbonate, not when they are neutralized by powerful acids: for wool, when fit to receive the dyes, and if it is designed to be dyed yellow, should boil two hours with one-tvvelfth or one-tenth of its weight, of sulphate of alum (common alum) observing proper precautions, and the use of a sufficient quantity of prepared weld plant boiled, &c.; or of quercitron bark, as will be shown in the processes of the different yellows. If it were yarn, and the threads cut in two, it would be found dyed throughout, and of a body and richness in proportion to the correct application of the various ingredients, and with due regard to time, weight, measure, &c.

In the process just mentioned, we may observe, that the quantity of alum and of the weld plant used will be found very considerable: from one twelfth to a fourth of alum, and, according to the French method, four or five times more weld than the quantity of the wool.

When a process of dyeing has been scientifically conducted, the wool will take so much of the alum that the bath will hardly taste of it; and afterwards take the colour of the dye bath out of it; so that the remaining liquor put into a glass will be nearly like water.

On the action of alum and tartar upon wool.

From the experiments of Dr. Ure, {Notes to Berthollet, vol. ii. p. 323.) it appears that alum has the property of increasing the solubility of cream of tartar; that as, in using alum and tartar, the wool is impregnated with alum and a large quantity of tartaric acid, these two salts should never be employed together, except when the colour is susceptible of being heightened and rendered brighter by acids, as is the case with cochineal, madder, and kermes. On the contrary, alum should never be employed for wools intended to be dyed with woad, or Brazil-wood, the colour of which is easily destroyed or altered by acids.

To conclude these preliminary observations, wool has a strong and powerful affinity for all dyeing materials; and, therefore, the processes for dyeing wool are, in general, by no means so complicated as those for dyeing cotton, silk, &c.; although some colours, even to these, are readily, and without a complication of processes, imparted.

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