A Treatise on Calico Printing, Of Bleaching.

A Treatise on Calico Printing, VOL. I-II
Printed for C. O'Brien, Bookseller, Islington, and fold by Bew, Paternoster-row: Richardson, Royal Exchange: Murray, Fleet-Street: And the Booksellers of Manchester, Glasgow, Dublin, &c.

(10) Meaning among printers that these processes are necessary for preparing the cloth to be printed; hence is printing-grounds the terms bleaching, or whitening is confined to laying goods on the grass, and more particularly after printing. It is hardly needful to say that bleaching, strictly speaking, means whitening, by whatever method it is per formed, therefore perhaps somewhat forcibly applied here, as it is net always that cloth sent down wants whitening.

(11) Wool, silk, flax, and cotton, possessing naturally an unctuous quality, it of course follows that they must undergo certain processes, in order to divest them of that quality, or it will prevent their imbibing any colour (cotton, however, has this qualify but in a very small degree) and this process is termed Bleaching, in general; but as particularly applied, it is called scouring of wool, ungumming of silk, whitening of thread, &c. and for this purpose it is found necessary to use occasionally acids or alkalies. Alkalies act most powerfully, because the substance to be removed is of an oily nature; and they are used either in a pure state, or else as a soap. Acids are afterwards used, for the purpose likewise of whitening, and to clear the cloth or other body of what alkalies do not remove. For cleansing wool, stale urine is made use of, which being alkaline, and combining itself with the oily quality of it, forms a soap, and produces the desired effect. Silk, naturally of a yellow colour, is boiled in soap and water, rather than subjected to fixed alkali, because of its being an animal substance, and hence more liable to be corroded; it is likewise in general [-] whitened by sulphur. The whitening of flax, linen, &c, is however performed with fixed alkali, as the noxious substance is more difficult to be removed than from wool, or silk. Lime is used by many bleachers, though exploded by others, particularly in Ireland, from its caustic power, when used alone.
Sour milk, whey, or an infusion of bran, or ryeflour, and other acids, such as verjuice, lemon juice, &c. were formerly only in use, but oil of vitriol, marine acid, and other more modern improvements, have now the preference.
The ancients cleansed their wool with a plant called by Pliny, radicula, and by Linnæus, gypsophila Struthion, the same which is called in the shops soap wort, used likewise for sulling, and taking out various spots; it is still used in some parts of Spain, instead of soap, the [-]llitory and marine colvolvulus; likewise the peplos or white spurge, these plants abounding with a kind of caustic milky juice., —See more of the ancients in the lection of Colour-making.

(12) Formerly, in this process of steeping, ryemeal, bran, or ley was used with warm water, t» produce a fermentation, in order to displace the foulness, chiefly contracted from dressing the threads with tallow and other articles, previous to weaving. But the practice is different now.—See the retrospect, and notes 6 and 7 to it.

* Printers are here asked, whether the confounding circumstance (see note 32) of goods printed alike coming up different in the copper, is not often owing to improper assortments in this case and whether, in possible cases, cloth of the same sort intended for the same pattern, had not better be all prepared at the same time, and put by separately?
Or, as it is usually termed Preparation. (10)

Though Bleaching in a general manner as practised among prosessed Bleachers, does not in every respect come under the consideration of Callico Printers, it may not be improper to say two or three words concerning it; two or three occasional references to it will therefore be given, subjoined as notes, rather than by in troducing them in the body of this work;(11) as what Callico Printers perform in this way is chiefly Ashing and Souring, and in a manner rather peculiar to themselves, as established by custom rather than founded on principles; the arrangement of the processes will therefore he as most generally practised, where the articles are intended to be printed, for perhaps no two grounds pursue the same modes, even in essentials.

REMARKS, &c. (12)

In the first place, the pieces should be [-] according to their qualities of texture and, as nearly as possible, their degrees of foulness; for much indeed depends on it. See the note below. *

They are then to be soaked (generally all night) in a receptacle entirely free scorn what-ever might stain-them; and so contrived, that it fresh supply of water [-] be admitted when needful, and the foul drawn off, or the scum, would subside and be injurious.

The receptacle, it perhaps need hardly be said, should not he covered with a plain board; but with one closely perforated, and that it be rather secured by posts placed betwixt it and the joists, rather than by weights; but if weights or weighty articles are used, they should not be of iron.

Respecting water, see the last note to maddering.

See likewise note 21 to general reflections.

It is however, here just said, if it be alkaline, syrup of violets turns it green. If acid, it turns it red. If aluminous, oil of tartar thickens it. If muddy, allum precipitates the foulness: if it contain iron, galls blacken it, &c. But above all, to procure pure water, a stil should be kept in every colour-house.

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