The London Encyclopædia: Part II. The Practise of Dyeing.

The London Encyclopædia: Part II. The Practise of Dyeing.


Kappale teoksesta:

The London Encyclopædia, or Universal Dictionary of Science, Art, Literature, And Practical Mechanics, Comprising A Popular View of The Present State of Knowledge.

By The Original Editor of The Encyclopædia Metropolitana, Assisted By Eminent Professional And Other Gentlemen.

In Twenty-Two Volumes

Vol. VII

London:
Printed For Thomas Tegg, 73, Cheapside;
R. Griffin & Co., Glasgow; Tegg and Co., Dublin; Also J. & S. A. Tegg, Sydney and Hobart Town.

1839

Part II. The Practise of Dyeing. (Alku)
s. 593-596


PART II.
THE PRACTISE OF DYEING.

102. Before we proceed to give directions for the various processes to be observed in the practise of dyeing, we shall take a brief view of M. Berthollet's observations on dyeing operations in general, which cannot fail to be interesting to the practical dyer.

103. 'It may be regarded,' says he, ' as a general principle, that processes performed in a great manufactrory are more advantageous than those which are insulated, since, from the subdivision of labor, each workman, occupied with a single object, acquires celerity and perfection in his employment, by which means the saving of time and labor becomes very considerable.

104. The principle is particularly applicable to the art of dyeing, as the preparation which remains after one operation may often be advantageously employed in another. A bath from which the coloring matter has been nearly extracted in the first operation may be used as a ground for other stuffs, or, with the addition of a fresh portion of ingredients, may form a new bath. The galls which have been applied to the galling of silk may answer a similar purpose for cotton or wool. From this it is evident that the limitations under which the art of dyeing labors

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in some countries must tend to obstruct its progress and improvement.

105. A dye-house should be situated as near as possible to a stream of water, and should be spacious and well lighted. It should be floored with lome and plaster; and proper means should be adopted to carry off water or spent vaths by forming channels or gutters, so that every operation may be conducted with the greatest attention to cleanliness.

106. The size and position of the boilers are to be regulated by the nature and extent of the operations for which they are designed. Excepting for scarlet and other delicate colors, in which tin is used as mordant, in which case tin vessels are preferable, the boilers should be of brass or copper. Brass, being less apt than copper to be acted on by means of chemical agents, and to communicate spots to the stuffs, is fitter for the purpose of a dyeing vessel. It is scarcely necessary to say that it is of the greatest consequence that the coppers be well cleaned for every operation; and that vessels of a large size should be furnished at the bottom with a pipe and stop-cock for emptying them; there must also be a contrivance above each copper to support the poles for the purpose of draining the stuffs which are immersed, so that the liquor may fall back into the vessel, and prevent waste.

107. Dyes from silk, where a boiling heat is not necessary, are prepared in throughs or backs, which are long copper or wooden vessels. The colors which are used for silk are extremely delicate. They must therefore be dried quickly, that they may not be long exposed to the action of the air, and that there may be no risk of change. For this purpose, it is necessary to have a drying room heated with a stove. The silk is stretched on a movable pole, which by the dyers is called a shaker. This is hung up in the heated chamber, and kept in constant motion to promote the evaporation.

108. For pieces of stuffs, a winch or reel must be used; the ends of which are supported by two iron forks which may be put up at pleasure in holes made in the curb on which the edges of the copper rest. Them anipulations in dyeing are neither difficult nor complicated. Their object is to impregnate the stuff to be dyed with the coloring particles, which are dissolved in the bath. For this purpose, the action of the air is necessary, not only in fixing the coloring particles, but also in rendering them more vivid; while those which have not been fixed in the stuff are to be carefully removed. In dyeing whole pieces of stuff, or a number of pieces at once, the winch or reel mentioned above must be employed. One end of the stuff is first laid across it, and, by turning it quickly round, the whole passes successively over it. By turning it afterwards the contrary way, that part of the stuff which was first immersed will be the last in the second immersion, and by this means the coloring matter will be communicated as equally as possible.

109. In dyeing wool in the fleece, a kind of broad ladder with very close rounds, called by the dyers of this country a scraw, or scray, is used. This is placed over the copper, and the wool is put upon it for the [...]

[Sivun loppuosa puuttuu]

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to be dyed, render them foul, and prevent the coloring matter from combining with them.

114. It is of much consequence to be able to distinguish the different kinds of water which some under the denomination of hard-water, that they may be avoided in the essential operations of dyeing; but to detect different principles contained in such waters, and to ascertain their quantity with precision, require great skill, and very delicate management of chemical operations, which the experienced chemist only can be supposed to possess.

115. One of these tests is the soap solution, by which it may be discovered whether water contain so large a portion of any of these saline matters as may be injurious to the processes. Salts which have earthy bases have the property of decomposing soap by the action of double affinity. The acid of the salt combines with the alkali of the soap, and remains in solution, while the earth of the salt and the oil of the soap enter into combination, and form an earthy product which is insoluble in water, and produces the curdling appearance which is the consequence of this new combination. Water, then which is limpid, which has no perceptible taste or smell, and has the property of dissolving soap without decomposition, is sufficientyly pure for the processes of dyeing. All waters which possess these qualities will be foind equally proper for these purposes.

116. But, as it is not always in the power of the dyer to choose pure water, means of correcting the water which would be injurious, and particularly for the dyeing of delicate colors, have been proposed. Water in which bran has been allowed to become sour, is most commonly employed for this purpose. This is known by the name of sours, or sour water. The method of preparing sour water is this: Twenty four bushels of bran are put into a vessel that will contain about ten hogsheads. A large boiler is filled with water, and when it is just ready to boil, it is poured into the vessel. Soon after the acid fermentation commences, and in about twenty hours the liquor is fit for use. Water which is impregnated with earthy salts, after being treated in this way, forms no precipitate when boiled.

117. Mucilaginous plants are sometimes boiled in the water for the purpose of correcting it, when a froth forms that is to be carefully skimmed off as it rises. The mucilage coagulates, carrying with it the earths which separate on the colatilisation of the carbonic acid, as well as those that are merely mixed with the water and which render it turbid.

The salts, however, which have an earthy base, and which are in general injurious to dyeing, do, in certain cases, serve to modify the colors when the object of the dyer is to obtain deep shades. In this way, for example, a crimson hue is given to the color produced by cochineal.