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

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


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. Of Dyeing Blue.
s. 599-602


OF DYEING BLUE

143. Of Dyeing Wool Blue - There are various processes employed gfor dyeing wool, silk, &c., of blue color, but the principal coloring matters made use of are indigo and woad. Archil, cochineal, turmeric, and logwood, are occasionally used as auxiliaries. Prussian blue also has, in some cases, been successfully employed in producing some very beautiful but fugitive shades of blue.

The vessels in which blue is dyed are called vats; they were formerly made of wood; in many instances they are still constructed of that material; lead, however, has been found superior, and in modern practice, cast iron is generally used. When the vat is made of wood, the liquor must be raised to the requisite heat in another vessel, and then transferred to it, a process attended with any inconveniences; when made of lead it is surrounded with brick work, of a single brick in thickness, which admits of a fire being placed under it for the purpose of warming the liquor.

144. Some dyers make use of iron vats which are warmed by steam, applied to the exterior of the vat; but the more common method is to use a vessel of cast iron, and to apply a gentle fire under it as occasion may require

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Before the introduction of indigo, blue was dyed with woad, this produced a color which was tolerably permanent, but rather faint; a very rich blue however is now obtained by the union of the two substances. The proportions in which these are used, vary according to the depth of shade required. The following is the process of preparing a vat as given by Quatrernere.

145. Into a vat of about seven feet and a half deep, and five and a hald in diameter, are thrown two bales of pastel or woad, previously broken, and together about 400 pounds wright; thirty pounds of weld are boiled in a copper for three hours, in a sufficient quantity of water, to dill the vat. To this decoction are added twenty pounds of madder and a basket of bran. The boiling is then continued half an hour longer. This bath is cooled with twenty buckets of water, and after it is settled, and the weld taken out, it is poured into the vat, which must be stirred with a rake all the time that it is running in, and for fifteen minutes longer.

146. The vat is then covere, and allowed to stand for six hours, when it is uncovered, and raked again for half an hour. The same operation must be repeated every three hours. When the appearance of blue streaks is perceived on the surface, eight or nine pounds of quick lime are added; the color then becomes of a deeper blue, and the vat exhales more pungent vapors. Immediately after the lime, or along with it, the indigo, which has been previously ground in a mill, with a small quantity of water, is put into the vat. The quantity is to be regulated by the intensity of the shake required. If, on striking the vat with a rake, a fine blue scum arises, no other preparation is required than to stir it with the rake twice in the space of six hours, to mix the ingredients completely. Great care should be taken not to expose the vat to the air, except during the time of stirring it.

147. Vats of this description are sometimes liable to accidents. A vat is said to be repelled, when, having previously afforded fine shades of blue, it appears black, without any blue streaks; and if on being stirred the black color becomes deeper, the vat at the same time exhales a pungent odor; and the stuff dyed in it comes out of a dirty gray color. These effects are ascribed to an excess of lime.

148. Different means are employed to recover a repelled vat. Some merely reheat it; while others add tartar, bran, urine, or madder. Hellot recommends bran and madder as the best remedy. If the excess of lime be not very great, it is sufficient to leave it at rest five or six hours, putting in a quantity of bran and three or four pounds of madder, which are to be sprinkled on the surface, and then it is to be covered up, and after a certain interval to be tried again. But if the vat has been so far repelled as to afford a blue only when it is cold, it must be left at rest to recover, and sometimes must remain whole days without being stirred with the rake.

149. When it begins to a[...] tolerable pattern, the bath must be reheated. In general this revives the fermentation; or it may be excited with bran and madder, and even with a basked or two of fresh pastel.

Hecquet d'Orval and Ribacourt adcise [...] satisfied without raking up, if the bath [...] slightly thrown back; but if the [...] more progress, to put into it some [...] bran enclosed in a bag, and to diffuse [...] it at the same time three or four punds of [...] in powder. The bag, after five or six [...] begins to float and is withdrawn, and the [...] is used. If the vat be not yet restored, the [...] operation is repeated.

Quatremere says, that he has re-established [...] vat which he had thrown back by a [...] lime; and that for this effect he [...] self with heating twice, and leacing [...]repose for two days, after which it [...] well characterised flower or bloom. He [...] again in repose for three days; and lastly [...]ing it for the third time, he found it to be restored.

150. The second accident, to which the [...] vat is subject, is putrefaction. When this accident occurs, the veins and the bloom disappear and its color becomes russet, the paste which is at [...] bottom rises up, the smell becomes [...].

Quatremere asserts, that, if a pattern of [...] blue be plunged into a vat thus [...] color becomes several shades lighter. Putrefaction takes place in a vat, because it has not been sufficiently furnished with lime. When [...] marks of putrefaction appear, we must [...] correct it, by adding lime and raking up. The operation must be repeated till the vat [...] stored; but great care is required to avoid [...] opposite extreme.

It appears, adds M. Berthollet, that a [...] distribution of lime is the object which [...] most attention in the conduct of a pastel vat. It moderates the fermentation of the pastel, and [...] the other substances that serve to [...] the indigo; for this effect, pushed too far, destroys the coloring particles. But too strong [...] action of the lime becomes too great an [...]. It is therefore proper to wait till the [...] lime disappears, undoubtedly by the [succeeded?] formation of carbonic acid, or the [source of the?] fermentation must be increased, or a [portion of the?] lime be saturated by a vegetable acid. Another use of lime is to hold in solution the [...]ing particles of indigo and of the pastel [...] are disoxygenated. Woad is employed [...] as pastel, but it appears that the [...] preparation, to which both are subjected, [...] essential. We have seen a skilful dyer [of linen?] employ for his vat the plant of woad dried; and assert that he derived more [...] from it than from ordinary woad.

151. The vat must be raked about two [hours?] before dyeing, and to prevent the sediment, [...] paste, from occasioning inequalities in the color, a kind of lattice formed of large cords, [...] cross, is introduced; and when wool is to be dyed in the fleece, a net with small [...] placed over this.

The wool or cloth being thoroughly [...] with clear water, a little warm is [...] and dipped into the vat, where it is [...] a longer or shorter time, according as the [...] is required to be more or less deep, [...] occasionally to air. The action of the [...]

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[...]ssary to change the green color given by the bath to a blue. In a rich bath it is difficult to have a uniform color to light blues: the best method of obtaining such shades, therefore, is to use vats nearly exhausted, and of a low temperature. Wool and cloth dyed blue, should be washed with great care, to carry off the particles not fixed in the wool, and those which are of sa somewhat deep blue, ought even to be carefully cleansed, by fulling with soap, ehich does not alter the color. Those designed to be dyed black, ought to be treated in the same manner; but it is not [...] necessary for those which are to be green, to be thus prepared.

152. The indigo vat is that which contains neither pastel nor woad. The vessel used for this preparation is a copper, which, being of a [...] figure, leaves between it and the brick[...]ork that surrounds it, and on which its brim [...]ests, an empty space sufficient to admit of the action of fire. Into this copper are poured about forty pails of water, in which have been boiled six pounds of salt and tartar, twelve ounces of madder, and six pounds of bran. This liquor is to be put into the vat, grounds and all: siz pounds of indigo ground in water are then to be put in, and after raking it carefully the vat is to be covered. A slow fire is to be kept up round it. Twelve hours after it is filled, it is to be raked a second time; and so on every twelve hours, till it become blue, which it will be in forty-eight hours. If the bath be well managed, it will be of a fine green, covered with copper colored scales, and have a blue scum or flower at the top. It may be observed, that the theory of this vat is the same as that of the foregoing, except that the indigo is here dissolved by alkali instead of lime. When this vat, which is much more easily managed than that of pastel, is in a proper state, it may be used for dyeing in the same manner as that described above.

153. M. Hellot describes two vats in which the indigo is dissolved by urine. Madder is added to it, and n the one vinegar, in the other alum and tartar, of each a weight equal to that of the indigo. The quantity of urine ought to be considerable. The solution of indigo, deprived of its oxygen by the urine and madder in fermentation, is due to the ammonia formed in the urine, either by the action of heat or fermentation. Hellot remarks, that an effervescence takes place on pouring in the solution of alum and tartar, which propably tends to stop the petrefaction. These vats are by no means comparable with those of pastel, or indigo; much less work being despatched by them; so that they are adapted only for small dye-houses.

154. Of Dyeing Silk Blue - Silk is dyed blue with indigo alone, without any proportion of woad. The proportion of indigo mentioned in the preparation of the indigo vat, and sometimes a larger, is employed, with six pounds of bran, and about twelve ounces of madder. According to Macquer, half a pound of madder for each pound of potassa, renders the vat greener, and produces a more fixed color in the silk. When the vat is come to, it should be refreshed with two pounds of potassa, and three or four ounces of madder; and, after long raked, in the course of four hours it is fit for dyeing. The temperature shuld be so moderated that the hand may be held in it.

155. The silk, after being boiled with soap, in the propoertion of thirty pounds of soap to 100 of silk, and well cleaned by repeated beetlings in a stream of water, must be dyed in small portions. When it has been turned once, of oftener, in the bath, it is wrung out and exposed to the air, that the green color may change to a blue. When the change is complete, it is thrown into clear water, and afterwards wrung out. Sillk dyed blue should be speedily dried. In damp weather, and in winter, it is necessary to conduct the drying in a chamber heated by a stove. The silk should be hung on a frame kept constantly in motion. To dye light shades, some employ vats that are nearly exhausted: but it ought to be observed, that the color thus obtained is less beautiful and less permanent than when fresh vats, containing a smaller quantity of indigo, are employed.

156. Some addition is required to be made to the indigo, to give silk a deep blue. A previous preparation is necessary, by giving it another color or ground. For the Turkey blue, which is the deepest, a strong bath of archil is first prepared. Cochineal is sometimes used, insted of archil, for the ground, to render color more permanent. A blue i given to silk by means of verdigris and logwood, but possesses little durability. It might be rendered more permanent, by giving it a lighter shade in this bath, then dipping it in a bath of archil, and, lastly, in the indigo vat.

157. When raw silk is to be dyed blue, such as is naturally white should be selected. Being previously soaked in water, it is put into the bath in separate hanks, as already directed for scoured silks; and, as raw silk combines more readily with the coloring matter, the scoured silk, when it can be conveniently done, should be first put into the bath. If archil, or any of the other ingredients, are required to give more intensity to the color, the mode of application is the same as that directed for scoured silk.

There are various other methods of conductiong this part of dyeing, described by M. D'Apligny, Quatremere, Bergman, Scheffer, &c., which we omit as not being of material importance to the practical dyer.

158. Of Dyeing Cotton and Linen Blue. - In communicating the blue color to these substances, the principal ingredient employed is indigo; but Prussian blue has been found to answer extremely well. According to Le Pileur d'Apligny, says M. Berthollet, the vat for dyeing cotton and linen is capable of holding about 120 gallons. The quantity of indigo employed is usually from six to eight pounds, finely ground, and boiled in a lee drawn off from double its weight of potassa, with a quantity of lime equal in weight to the indigo. During the boiling, which is to be continued till the indigo is thoroughly penetrated with the lee, the solution must be constantly stirred, to prevent the indigo from being injured by adhering to the bottom of the vessel.

159. During this process, another quantity of quick-lime, equal to the indigo, is to be slaked. Twenty quarts of warm water are added, in which

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is to be dissolved a quantity of sulphate of iron, equal to twice the weight of the lime. The solution being completed, it is poured into the vat, which is previously half filled with water. To this the solution of indigo is added, with that part of the lie which was not employed in the boiling. The vat must bow be filled up nearly to the top. It must be raked twice or thrice every day till it is completely prepared, which is generally the case in forty-eight hours, and sometimes sooner, as it depends on the temperature of the atmosphere. A small proportion of bran, madder, and woad, is recommended by some to be added to this vat.

160. The process which is followed at Rouen, and described by Quatremere, is more simple. The vats, which are constructed of a kind of flint, are coated within and without with fine cement, and are arranged in one or more parallel lines. Each vat contains four hogsheads of water. The indigo, to the amount of eighteen or twenty pounds, bein macerated for a week in a caustic lie, strong enough to bear an egg, is ground in a mill; three hogsheads and a half of water are put into the vat, and afterwards twenty pounds of lime. The lime being thoroughly slaked, the vat is raked, and thirty-six pounds of copperas are added, and, when the solution is complete, the ground indigo is poured in through a sieve. It is raked seven or eight times the same day, and, after being left at the rest for thirty-six hours, it is in a state fit for dyeing.

161. In extensive manufactories, it is necessary to have vats set at different times. In conducting the process of dyeing, the stuffs are first dipped in the most exhausted var, and then regularly proceeding from the weakest to the strongest, if they have not previous ly attained the desired shade. The stuffs should remain in the bath only about five or six minutes, for in that time they combine with all the coloring matter they can take up. After they have been dipped in a vat, it should not be used again till it has been raked, and stood at least twenty-four hours, unless it has been lately set, when a shorter period is sufficient.

162. After the stuffs have been dipped three or four times in a vat, it becomes vlack, and no blue or copper-colored streaks are seen on the surface after raking it. It must then be renewed, by adding four pounds of copperas with two of quicklime, after which it must be raked twice. In this way a vat may be renewed three or four times; but the additional quantity of ingredients must be diminished as the strenght of the vat is exhausted.

163. A vat which is still more simple and more easily prepared, has been recommended by Bergman. The proportion of the ingredients which he has directed to be employed is the following: - To three drachms of indigo reduced to powder, three drachms of copperas, and three of lime, add two pints of water. Let it be well raked, and in the course of a few hours it will be in a proper state for dyeing.

164. Haussmann employs a still less proportion of indigo. For about 500 gallons of water he takes thirty-six pounds of quick-lime, slaked in about twenty-five gallons of water, with which the indigo is to be mixed in the proportion [...] ten to twenty pounds, well ground. [...] then dissolves thirty pounds of sulphate of [iron?] in about fifteen gallons of water. The [...] left at rest for fifteen minutes; the vat is [...] filled, and gently and constantly stirred. When a deeper shade is wanted, and particularly when linen is to be dyed, the proportion of [...] should be greater; but the shade depends very much on the time the stuffs remain in the vat, and the times it has been used. When the vat becomes turbid, the process of dyeing must be interrupted, till it has been again raked, and the supernatant liquor become transparent. If the effects of the lime fail, a new quantity [...] added; and if the iron cease to produce the effect on the indigo, a new portion must be [...] added, observing to have a greater quantity of lime than is necessary to saturate the sulp[...] acid.

165. When the indigo appears to be exhausted fresh portions are to be added; the vat is to [be?] raked several times, and allowed to settle, after which it is again fit for use. In this way Mr. Haussmann says he preserved a vat for two years; and had not been for the accumulation of sediment, which prevented the stuffs from being immersed to a sufficient depth, it [...] have been continued in use for a much longer time. It is proper to add, that Mr. Haussmann found, that a pattern of cloth dipped in [...] acidulated with sulphuric acid, immediately after it was taken out of the bath, became of a much deeper blue than a similar pattern exposed to the air, or another dipped in river water.

166. A remarkably fine blue is produced from a solution of indigo in sulphuric acid, to which the name of Saxon blue is given, from the circumstance of its having been discovered at Gro[...]senhayn in Saxony, by counsellor Barthi, about the year 1740.

167. The following, according to Berthollet, is the process of preparing this dye to Berg[man?]

He employed one part of indigo to eight parts of acid, keeping the mixture in a temperature of between 86° and 104° Fahrenheit, and he reckoned that one part of indigo, thus dissolved, was sufficient to give a deep blue color [...] times its weight of wool. Poerner used one part of indigo to four of sulphuric acid. To prepare the wool or cloth for this bath, it is first boiled with alum and tartar. The wool receives the finest as well as fullest color during the first immersion; but lighter, though duller shades, may be given to other portions by the same bath which partially exhausted. The deeper shades are more advantageously given by adding the solution of indigo to the bath, in successive portions, and raising the stuffs on the winch previously to each addition.