liquor, and the stuff passed through it, so as to produce a light shade; more solution of iron is then to be added to produce a deeper shade, and so on till the stuff acquire the requisite color.

If in this operation we go beyond the mark, the color must be darkened as before; but repeating these operations is prejudicial to the stuff, so that we should endeavour to catch the proper shade at once, by taking it occasionally out of the bath. Care must be taken that the bath do not boil, and that it be rather warm than too hot. In whatever manner grays are dyed, they should be immediately washed in a large body of water, and the darkest may even require soap to cleanse them. It is sometimes required to give grays a tint of another color, as a nut, agate, or reddish cast. In this case, having given a tint more or less blue according to the object intended, the stuffs are dipped in the remains of some cochineal liquor, that has served for dyeing either scarlet or violet, adding galls, logwood, madder, &c.; they are then browned more or less deep with a solution of iron. For the nut gray, yellow wood and logwood are added to the galls, and the stuff is to be dyed from white.

140. Silk takes all grays, except black-gray, without previous aluming. The bath is composed of fustic, logwood, archil, and sulphate of iron. These ingredients are varied according to the tint to be given. Thus more archil is employed for grays that are to have a reddish cast, more fustic for those that should incline to a russet or green, and more logwood for those that are to be of a darker gray. For iron-gray logwood and solution of iron are only employed. But black-gray requires aluming; after which the silk is taken to the river, and then dipped in the weld bath. A part of this bath is thrown away, and its place supplied with logwood liquor. When the silk is impregnated with this, a sufficient quantity of solution of iron is added, and, as soon as it has acquired the proper shade, it is to be washed and wrung carefully. If the gray should happen to be too dark, the silk is dipped in a solution of tartar, and afterwards in warm water; and, if by these means the color be weakened too much, the silk is again dipped in a bath of dye that is quite fresh.

141. Linen and Cotton should have a blue ground imparted to them for black-gray, irongray, and slate-gray, but for no other. All the shades require a galling proportionate to the gray to be produced. Gall baths that have before served for other purposes are often employed. When the stuff has been galled, wrung, and dried, it is dipped in a vessel of cold water, to which is added a proper quantity of the bath from the black cask, and of a decoction of logwood. The stuff is worked in separate portions, and afterwards washed and dried properly. Two other processes for dyeing gray are given by M. Pileur d'Apligny, which, according to him, produce a more permanent color. They are these. 1. The yarn is galled, dipped in a very weak path of the black cask, and then maddered: 2. The yarn is dipped in a very hot solution of tartar, wrung gently and dried. It is then dyed in a decoction of logwood. After this operation

it appears black; but, on working it attentively in warm soap suds, the surplus of the dye is discharged, and it remains of a durable slategray.

142. A process, says M. Berthollet, the success of which is known to us, consists in taking a very diluted solution of acetate of iron (it is sufficient to add a little of this acetate to a quantity of water), and a decoction of sumach, also very dilute. The cotton is passed in succession from one liquor to the other, till the wished for shade be attained. The finish is given by passing through a water slightly acidulated by sulphuric acid, otherwise the sumach gives a russet hue. By the same process may be obtained with nutgalls less lively grays; and the alder bark affords an agreeable one, which borders on hazel.

A skilful manufacturer of Rouen has communicated to us the following process, which he makes use of successfully for cotton velvets. A galling is given with an equal quantity of gall nuts and logwood, after which a bath of cold water is administered, and next another bath of water, in which there has been dissolved a weight of sulphate of iron, equal to the one-half of the preceding ingredients. After working the cotton about a quarter of an hour in this bath, it is rinsed in cold water, and brightened.

For this purpose a bath of tepid water is used, to which one-eightieth of decoction of weld, and a little alum, are added. The cotton is left about twenty minutes in this bath, after which it is washed in cold water, and dried.

By modifying the doses of the ingredients, grays, from pearl-gray to the deepest gray, may be thereby obtained.

For grays on printed goods, the same mordant is impressed as for a clear violet, and sumach or gall-nuts are employed according to the shade that is desired.

OF DYEING BLUE.

143. Of Dyeing Wool Blue.-There are various processes employed for 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 ut 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 many 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.

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 Quatremere.

145. Into a vat of about seven feet and a half deep, and five and a half in diameter, are thrown two bales of pastel or woad, previously broken, and together about 400 pounds weight; thirty pounds of weld are boiled in a copper for three hours, in a sufficient quantity of water, to fill 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 covered, 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 shade 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 and 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 basket or two of fresh pastel.

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

Quatremere says, that he has re-established a vat which he had thrown back by a surcharge of lime; and that for this effect he contented himself with heating twice, and leaving it then in repose for two days, after which it afforded a well characterised flower or bloom. He left it again in repose for three days; and lastly, heating it for the third time, he found it to be restored.

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

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

It appears, adds M. Berthollet, that a just distribution of lime is the object which demands most attention in the conduct of a pastel vat. It moderates the fermentation of the pastel, and of the other substances that serve to disoxygenate the indigo; for this effect, pushed too far, destroys the coloring particles. But too strong an action of the lime becomes too great an obstacle. It is therefore proper to wait till the excess of lime disappears, undoubtedly by the successive 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 the lime is to hold in solution the coloring particles of indigo and of the pastel, which are disoxygenated. Woad is employed as well as pastel, but it appears that the preliminary preparation, to which both are subjected, is not essential. We have seen a skilful dyer of Rouen employ for his vat the plant of woad simply dried; and assert that he derived more advantage from it than from ordinary woad.

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

The wool or cloth being thoroughly wette with clear water, a little warm is pressed out, and dipped into the vat, where it is moved about a longer or shorter time, according as the color is required to be more or less deep, taking it out occasionally to air. The action of the air is ne

cessary to change the green color given by the bath to a blue. In a rich bath it is difficult to give 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 a somewhat deep blue, ought even to be carefully cleansed, by fulling with soap, which does not alter the color. Those designed to be dyed black, ought to be treated in the same manner; but it is not so 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 conical figure, leaves between it and the brickwork that surrounds it, and on which its brim rests, an empty space sufficient to admit of the action of the fire. Into this copper are poured about forty pails of water, in which have been boiled six pounds of salt of tartar, twelve ounces of madder, and six pounds of bran. This liquor is to be put into the vat, grounds and all: six 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 De 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 in 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 probably tends to stop the putrefaction. 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 being raked, in the course of four hours it is fit

for dyeing. The temperature should be so moderated that the hand may be held in it.

155. The silk, after being boiled with soap, in the proportion 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, or 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. Silk 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 also sometimes used, instead of archil, for the ground, to render the color more permanent. A blue is 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 conducting 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

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 now 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, being 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 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 vat, and then regularly proceeding from the weakest to the strongest, if they have not previously 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 black, 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 strength 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 of from ten to twenty pounds, well ground. lle then dissolves thirty pounds of sulphate of iron in about fifteen gallons of water. The whole is left at rest for fifteen minutes; the vat is then filled, and gently and constantly stirred. When a deeper shade is wanted, and particularly when linen is to be dyed, the proportion of indigo 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 must be added; and, if the iron cease to produce the effect on the indigo, a new portion must be also added, observing to have a greater quantity of lime than is necessary to saturate the sulphuric 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 it not been for the accumulation of sediment, which prevented the stuffs from being immersed to a sufficient depth, it might 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 water 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 Grossenhayn in Saxony, by counsellor Barthi, about the year 1740.

167. The following, according to Berthollet, is the process of preparing this dye by Bergman.

He employed one part of indigo to eight parts of acid, keeping the mixture in a temperature of between 86° and 104° of Fahrenheit, and he reckoned that one part of indigo, thus dissolved, was sufficient to give a deep blue color to 260 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 when partially exhausted. The deeper shades are most 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.

OF DYEING RED.

168. Red colors are known by different names according to their degrees of intensity, as crimson, scarlet, &c., besides innumerable shades that fall under no particular denomination. The substances usually employed in dyeing red, are cochineal, madder, kermes, lac, carthamus, Brasil-wood, archil, and logwood. All these, with