The Engineer's and Mechanics Encyclopædia: (Wool:) The processes employed in dyeing...

The Engineer's and Mechanics Encyclopædia,
comprehending practical illustrations of the machinery and processes employed in every description of manufacture of the British Empire.
With nearly Two Thousand Engravings.
By Luke Hebert, civil engineer, edifor of the History and Progress of the Steam Engines, Register of Arts and Journal of Patent Inventions, etc.
In two volumes.
VOL. II.
London: Thomas Kelly, 17, Paternoster Row.
MDCCCXXXVI (1836).

(Tekstiin lisätty kappaleita lukemisen helpottamiseksi. // Some paragraphs added to the original text for making reading easier.)The processes employed in dyeing woollen cloth differ considerably from those used in silk and cotton. The oil is first removed by the operations of the fulling-mill, where it is beaten with large beetles in troughs of water, mixed with fuller's-earth; and when thoroughly cleansed it is ready for dyeing.

The only colours used in dyeing wool blue, are woad and indigo, which are both substantive colours, that is, they are permanent without requiring a mordant. Quatremere recommends the following mode of preparing a blue vat: —
Into a vat about seven and a half feet deep, and five and a half broad, are thrown two balls of woad, weighing together about 400 lbs., first breaking them; thirty pounds of weld are boiled in a copper for three hours, in a sufficient quantity of water to fill the vat; when this decoction is made, twenty pounds of madder and a basket full of bran are added, and it is boiled half an hour longer. This bath is cooled with twenty buckets of water; and, after it is settled, the weld is taken out, and it is poured into the vat; all the time it is running in, and for a quarter of an hour after, it is to be stirred with a rake. The vat is then covered up very hot, and left to stand six hours, when it is raked again for half an hour, and this operation is repeated every three hours. When blue veins appear on the surface of the vat, eight or nine pounds of quick lime are thrown in. Immediately after the lime, or along with it, the indigo is put into the vat, being first ground fine in a mill, with the least possible quantity of water (it is now usually ground dry.) When it is diluted to a semi-fluid consistence, it is drawn off at the lower part of the mill, and thrown thus into the vat. The quantity of indigo depends upon the shade of colour required. From ten to thirty pounds must therefore be put to the vat now described, according to the occasion.

If, on striking the vat with the rake, a fine blue scum arises, it is fit for use, after being stirred twice with the rake in six hours, to mix the ingredients. Great care should be taken not to expose the vat to the air, except when stirring it. As soon as that operation is over, the vat is covered with a wooden lid, on which are spread thick cloths, to retain the heat as much as possible. Not withstanding this care, the heat is so much diminished at the end of eight or ten days, that the liquor must be re-heated, by pouring the greater part of it into a capper over a large fire; when it is hot enough, it is returned into the vat, and covered as before.

This vat is liable to two inconveniences: first, it runs sometimes into the putrefactive fermentation, which is known by the fetid odour it exhales, and by the reddish colour it assumes. This accident is remedied by adding more lime. The vat is then raked: after two hours, lime is put in, the raking performed again, and these operations are repeated till the vat is recovered; secondly, if too much lime is added, the necessary fermentation is retarded; this is re medied by putting in more bran or madder, or a basket or two of fresh woad.

When cloth is to be dyed, the vnt is raked two hours before the operation; and to prevent it from coming in contact with the sediment, which would cause inequalities in the colour, a kind of lattice of large cords, called a cross, is introduced; when unmanufactured wool is to be dyed, a net with small meshes is placed over this. The wool or cloth, being thoroughly wetted with lukewarm water, is pressed out, and dipped into the vat, where it is moved about a longer or shorter time, according as the colour is intended to be more or less deep, taking it out occasionally to expose it to the air, the action of which is necessary to change the green colour, given the stuff by the bath, to a blue. Woollen and cloth dyed in this manner ought to be carefully washed, to carry off the loose colouring matter; and, when they are of a deep hue, soap should be used, as it will only cleanse and not injure the colour. The more perfectly the wool has been scoured, the better it will receive the dye.

A vat which contains no woad, is called an indigo-vat. For this vat, the indigo is rendered soluble in water by potash instead of lime; a copper vessel is used, and six pounds of potash, twelve ounces of madder, and six pounds of bran, are boiled with every 120 gallons of water; six pounds of finely-ground indigo are then added, and, after carefully raking it, the vat is covered, und a slow fire kept round it. Twelve hours afterwards, it is to be ruked a second time, and this operation is to be repeated at similar intervals of time, till the dye becomes blue, which will generally happen in forty-eight hours. If the bath be properly managed, it will be of a green colour, covered with coppery scales, and a fine blue scum.

The dye called Saxon blue is made with the solution of indigo in sulphuric acid. Take four parts of sulphuric acid, and pour them on one part of indigo, in fine powder; let the mixture be stirred for some time, and after it has stood twenty-four hours, add one part of dry potash; let the whole be again well stirred, and after it has stood a day and a night, add gradually more or less water. The cloth to be dyed, must be prepared with tartar and alum, and more or less indigo must be put into the bath, according to the shade required. For deep shades, also, the cloth must be passed several times through the bath; light shades may be dyed after deep ones, but they will not have the lustre given by a fresh bath.

Reds are a very important class of colours, and are furnished by a great number of substances. They all depend, either for their fixedness or beauty, upon the use of mordants; the principal of them are kermes, cochineal, archil, madder, carthamus, and Brazil-wood. Pewter boilers, or well-tinned copper, must be used in preparing all red baths.

The shades of red are usually distinguished into three classes; namely, the madder red, crimson, and scarlet. Madder is employed for coarse goods. It gives out its colour to water; and the bath prepared with it is not made hotter than what the hand can bear, until the wool has been in it about an hour, when it may be boiled for a few minutes just before the wool is taken out. It may be used in the proportion of one-third or one-fourth of the wool dyed. Cloths are prepared for the madder-bath, by boiling them for two or three hours in a solution of alum and tartar; after having been taken out of which, they are left to drain for a few days in a cool place before they are dyed. The use of archil gives a fine but transient bloom to the madder dye. Archil and Brazil-wood, from their perishableness, are seldom used to wool, except in this way, as auxiliaries.

When sulphate of copper is employed as the mordant, madder dyes a clear brown, inclining to yellow. Tin brightens its colour, but not materially.

Kermes has not been much used since the art of brightening cochineal with tin was discovered, as it has not so fine a bloom as the latter dye, though it possesses greater durability. Kermes imparts its colour to water; and the quantity of it used, is, for a full colour, at least three-fourths of the weight of the wool employed. The wool is put in at the first boiling, after having been previously prepared by boiling it for half an hour in water with bran, and afterwards two hours in another bath, with one-tenth of tartar dissolved in sour water, and then leaving it for a few days in a linen bag.

The red colour of the flowers of carthamus is extracted by a weak alkaline ley, and precipitated by lemon juice or sulphuric acid, but is chiefly used for silk and cotton. The precipitate is used in dyeing, and is called saffower or bastard saffron.

A crimson colour, inclining to violet, is the natural colour of cochineal, which yields most of its colouring matter to water, and, by the addition of a little alkali or tartar, the whole of it is extracted. To dye crimson by a single process, a solution of two ounces and a half of alum, and an ounce and a half of tartar, with an ounce of cochineal, is employed for every pound of stuff. A little nitromuriate of tin must be added for a fine crimson. Archil gives to crimsons that fine dark shade which is called bloom, but this soon disappears, by exposure to the air and light. For pale crimsons, the quantity of cochineal is reduced, and madder substituted.

Dr. Bancroft first suggested that scarlet was a compound of crimson and yellow, and he founded upon this idea, a more economical mode of producing it than had previously been used. He gives the following directions for dyeing scarlet: —
One hundred pounds of cloth are to be put into a tin vessel, nearly filled with water, with which about eight pounds of the murio-sulphuric solution of tin have been previously mixed. The liquor is made to boil, and the cloth is turned through it by the winch, for a quarter of an hour, in the usual manner. The cloth is then taken out, and four pounds of cochineal, with two pounds and a half of quercitron bark in powder, put into the bath and well mixed. The cloth is then returned into the liquor, which is made to boil, and the operation is continued as usual, till the colour be duly raised, and the dyeing liquor exhausted, which will usually happen in about fifteen or twenty minutes, alter which, the cloth maybe taken out and rinsed. In this method, the labour and fuel necessary in the common process for the second bath are saved; the operation is finished in much less time; all the tartar will be saved, as well as two-thirds of the expense of the solvent for the tin, and at least one-fourth of the cochineal usually required; the colour, at the same time, will not be in any respect inferior to that produced in the ordinary way, at so much more trouble and expense, and it will even look better by candle-light than others.

By omitting the quercitron-bark, the above process will afford a rose-colour. Scarlet may be changed to crimson by boiling the cloth in a solution of alum till the shade desired is obtained. Alkalies and earthy salts in general have the same effect as alum.

Yellow is a colour but rarely required in the dyeing of wool, yet, as it frequently forms the base of other colours, it may be proper to notice it. Weld fustic, and quercitron bark, furnish the best yellows: weld is a plant which is both cultivated and grows wild in this country; the stem is slender, and rises to the height of three or four feet; the entire plant is used in dyeing, and is gathered when it is ripe: the shortest and slenderest stems are the most esteemed. Fustic is the wood of a large West Indian tree. Quercitron grows in great abundance in North America, and is there called yellow oak; its bark is the only part used for dyeing.

The colours obtained from weld and quercitron both nearly resemble each other in shade, and also in durability, which is not great; but the bark containing the largest quantity of colouring matter is not only the most convenient to use, but iiiion the whole the cheapest. Dr. Bancroft has given the best directions for its use. He directs a deep and lively yellow to be thus prepared for wool: —
Let the cloth be boiled for an hour or more, with about one-sixth of its weight of alum dissolved in a sufficient quantity of water; then plunge it with out rinsing into a bath of warm water, containing in it as much quercitron bark as equals the weight of the alum employed as a mordant. The cloth is to be turned through the boiling liquid until it has acquired the intended colour. Then a quantity of clean powdered chalk, equal to the hundredth part of the weight of the cloth, is to be stirred in, and the operation is completed.

The object which the dyer has in view is to give his stuffs a uniform and durable colour, at the same time that he entirely preserves their original texture. He therefore uses colours in solution, in order that their particles may apply themselves to the individual fibres of the stuff, according to their affinity for it. When, for example, a quantity of wool, freed from all impurity, is dipped into the solution of any colouring mntter, if the fibres of the wool have a stronger attraction for the colouring matter than the water or other menstruum which holds that colour in solution, the colouring matter will leave its solvent, and apply itself to the wool, which will by that means be dyed; its fibres will have become covered with colouring matter; and if their attraction for it be so strong that the action of soap, air, and light, or other ordinary means of exposure, shall have no perceptible effect in decomposing the combination, or in other words, of injuring its tinge, the colour is said to be permanent; so that dyeing is in fact a chemical process, and the application of both animal and vegetable bodies depends on their chemical affinities.