dyed on a blue ground, and that the colour will be lafting, leave fome blue marks at the end of the cloth; this is done by fixing pieces of lead in fuch parts, which fecure them from the action of the black liquor.-That the dye has been thus regularly applied, may be difcovered with greater certainty, by boiling the cloth to be tried in a folution of alum and tartar: a blueish black will remain, if a blue ground has first been given; but if it has been dyed directly from the white, it will now look of a muddy reddish brown. This is the effay liquor for black cloths, directed in the new French regulations, which were drawn up from the experiments of Dufay, and published at the end of Hellot's Art de teindre.

After fome further general and pertinent obfervations on this fubject, our author fays, In the dying of black, as in most other colours, there are confiderable variations in the practices of different workmen, which it would be difficult and even ufelefs to collect. I fhall here defcribe two proceffes, which I have often tried in finall, and which appeared to me to be the best.'

Black with galls, logwood, and vitriol.

A hundred pounds of woollen cloth, dyed firft to a deep blue, require for the black dye, about five pounds of vitriol, five of galls, and thirty of logwood. Thefe, as I am informed by an experienced artist, are the quantities generally allowed by our dyers.

The galls, beaten into moderately fine powder, and tied up in a bag, are boiled for a little time in a copper of water fufficient for working the cloth in. The blued cloth, after being fteeped in river water and drained, that it may be every where thoroughly moift, but not fo as to drip, is in this ftate put into the boiling decoction of the galls, and kept turning therein for two hours or more, the bag of galls being now and then fqueezed, that the virtue of this drug may be more effectually extracted and communicated to the cloth.

The logwood, rafped or shaved into small chips, or rather ground into powder, is boiled in another copper for feveral hours, this wood giving out its colour exceeding difficultly. The logwood liquor is moft commonly prepared a confiderable time before it is ufed, its colour being found to improve in keeping.

The logwood decoction being made of a fcalding heat, but not quite boiling, the vitriol is thrown into it, and as foon as this is diffolved, the galled cloth is put in. A boiling heat should never be used after the addition of the vitriol, not only as it would needlessly augment the corrofive power of the falt, but likewife as it would injure the beauty of the colour, by hastily REV. April 1766.

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extricating part of the ferrugineous matter of the vitriol in am ochery form, before it can come fufficiently in contact with the aftringent fubftance with which the cloth is impregnated. The cloth is inceffantly turned in the liquor, that it may receive the colour uniformly, and now and then taken out and aired for a moment; which contributes to fecure the colour, and at the fame time affords an opportunity of judging of its deepness.

After about two hours continuance in the dye, the cloth is found to have received a good black, and is then taken out, washed with cold water, and paffed through the fulling-mill. The fuperfine cloth is three times fulled with warm folution of foap, which not only difcharges the fuperfluous colour that would otherwife ftain the fkin or linen, but contributes alfo to foften the cloth itself by mortifying the acid.'

Black dye with verdegris.

For fome of the fuperfine black cloths, a little verdegris is ufed by our dyers, and this addition appears among the French to be more frequent. Mr. Hellot, after trial of sundry proGefies, gives the following, as being the heft, or as that which produces the fineft velvet black on cloth, and which accordingly is followed in the beft dye-houses in France.

For a hundred pounds of blue cloth; ten pounds of logwood chips, and the fame quantity of Aleppo galls in powder, are tied up together in a bag, and boiled in a middling copper, with a fuitable quantity of water for twelve hours.

One third of this decoction is taken out into another copper, and two pounds of powdered verdegris added to it. In this mixture, kept gently boiling, or rather only scalding hot, the cloth is dipt, and turned without ceafing, for two hours; after which it is taken out and aired.

Another third of the decoction is laded out into the fame copper, eight pounds of green vitriol added, and the fire flackened about half an hour. The vitriol being now all diffolved, the cloth is put in and worked for an hour, and then taken out and aired again.

The remaining third of the decoction in the first copper is then put to the other two in the fecond, the bag of galls and logwood being well preffed out. Fifteen or twenty pounds of fumach are now added; and as foon as the copper begins to boil, two pounds more of vitriol are thrown in, with fome cold water to cken the heat. The cloth is kept in for an hour, then taken out and aired, dipt a fecond time, and kept turning for an hour longer.

The clo h, now compleatly dyed, is washed in a river, and fcowered in the fulling-mill till the water comes from it colour

lefs.

lefs. It is then paffed through a copper of weld or woold, prepared as for dying yellow, which is fuppofed to foften the cloth and confirm the colour.

This procefs affords a very fine black, but is too expenfive to be followed by our dyers, the fire and manual labour of the black dye, as here defcribed, amounting to more, as I am informed by a perfon converfant in this bufinefs, than the dyer is paid for the whole dye of the above quantity of fuperfine cloth, including the blue ground. The quantities of vitriol and galls may be diminished, and the time of boiling greatly fhortened. The paffing through weld liquor, after fcowering with foap, is entirely unneceffary; though probably it may be of ufe where the fcowering is not complied with; not however in virtue of the weld itself, but of the alcaline falt with which the decoction of it is generally prepared by the dyers, fo that the weld liquor does no more than fupply the place of foap.

Both in this and the foregoing procefs, the liquor remains black after the dying of the cloth is finished, and communicates a dilute black, that is a grey colour, to as much fresh cloth as can be conveniently worked in it.'

The remaining parts of this fection are employed in giving an account of the method of dying cloth grey;-dying wool black;-of a black dye without galls, by means of other vegetable aftringents, viz. oak bark, oak wood, fumach, uva urfi, &c.-and concludes with an account of the black dye from a combination of colours.Dr. Lewis next proceeds to the confideration

Of dying filk black.

There is a peculiar matter which gives a harfhnefs and colour to raw filk, and for the extracting of which, the alcaline falts, either in their pure ftate or made into foap with oils, are the proper menftrua: but these menftrua are likewife found to have a confiderable action, upon the fubftance of the filk itself; infomuch that in the common procefs for cleansing this fubject, its strength is certainly diminished; the workmen allowing that a thread of filk boiled, is not so strong as when raw and if the alcaline falt is used without being formed into a foap, and the boiling continued for a longer time, the filk becomes an incoherent friable mafs, not much unlike papier maché. Great

* Weld, here mentioned by our author, is a vegetable fubject, cultivated in great quantities in fome parts of England, for the purpose of dying yellow. The wool is firft to be boiled in a folution of allum and tartar, and after it is thus prepared, it is again to be boiled in five or fix times its quantity of weld; and by this process we obtain a very elegant yellow.

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nicety therefore is requifite to manage this part of the procefs. in fuch a manner, as to diffolve the particular matter which gives the harshness, and yet to damage the filk as little as poffible.

Mr. Macquer reckons it a difficult and complex affair to com municate black to filk; but experience, Dr. Lewis fays, has abundantly fhewn the contrary; and from his own obfervations; and the particulars of a procefs which Mr. Macquer relates as followed in the manufactories of Gours and Gines, he concludes, that filk is not more averfe than wool to the receiving the black dye; and that a good black may be dyed on filk, with the fame materials, in the fame method, and with the fame difpatch, as on wool or woollen cloth. This is further confirmed by the procefs defcribed in the next fection, for dying hats black. The method of our hatters, as I have been informed, fays Dr. Lewis, does not differ materially from that of the French, defcribed in the encyclopedie, which is as follows: An hundred pounds of logwood, twelve pounds of gum, and fix pounds of galls, are boiled in a proper quantity of water, for fix hours; after which, about fix pounds of verde gris and ten of green vitriol are added, and the liquor kept just immering, or of a heat a little below boiling. Ten or twelve dozen of hats are immediately put in, each on its block, and kept down by crofs bars for about an hour and a half: they are then taken out and aired, and the fame number of others put in their room. The two fets of hats, are thus dipt and aired alternately, eight times each; the liquor being refreshed each time with more of the ingredients but in lefs quantity than at first.

This procefs affords a very good black on woollen and filk fluffs as well as on hats, as we may fee in the fmallest pieces of both kinds which are fometimes dyed by the batters. The workmen lay great ftrefs on the verdegris, and affirm that they cannot dye a hat black without it: it were to be wished that the ufe of this ingredient was more common in the other branches of the black dye; for the hatters dye, both on filk and woollen, is reckoned a finer black than what is commonly produced by the woollen or the filk dyer.'-Our author's next inquiry is into the method

Of dying linen and cotton black.

The black vitriolic dye, though very durable on the fubflances hitherto mentioned, is perifhable on linen and cotton; and a method of communicating a full and durable black to thefe fubjects, has long been one of the defiderata in our art of dying. Dr. Lewis has made a number of experiments, but

could

could bring no procefs to fuch a degree of perfection as to produce the defired effect.There is a curious differtation of the Abbé Mazcas on the red printed cottons of the East Indies, in which he defcribes a method practifed by the Indians, of impregnating their cotton with an animal matter in order to its receiving the red colour. This procefs Dr. Lewis endeavoured to imitate; and tried whether the fame, or a fimilar animal impregnation, would difpofe the fubject to retain the black as effectually as the red dye. The black thus dyed, held the colour better, but not to fuch a degree as to be interefting to the workman. This fhew of fuccefs however, in an unfavourable feason, renders the experiment worthy of being tried again in more advantageous circumftances.

Some printed linens and cottons, fays our author, have a durable black ftain, which, as I am informed by an ingenious and skilful artist, is made with madder and a folution of iron. A quantity of iron is put into four ftrong beer; and to promote the diffolution of the metal, the whole is occafionally wel tirred, the liquor at times drawn off, the ruft beaten off from the iron, and the liquor poured on again: a length of time is required for making the impregnation perfect, the folution being reckoned unfit for ufe till it has food at least a twelvemonth. This folution ftains linen yellow, and of different fhades of buff colour, and is the only known material by which thefe colours can be fixed on linen. The cloth, ftained deep with iron liquor, being afterwards boiled with madder, without any other addition, becomes of the dark colour which we fee on printed cottons and linens, which, if not a perfect black, has a very near resemblance to it. It is fubmitted to the confideration of those whom it may concern, whether this fixt colour would not be preferable, on linen thread, to the perishable black with which thread has hitherto been dyed. It is probable, that even a better black might thus be dyed on thread, than that which the printer on linen produces; for in this laft bufinefs, while fome parts of the linen are ftained deep with the iron liquor, in order to their being made black, others are stained paler, with the fame liquor diluted with water, for making purple; and others defigned to be red, are prepared with a folution of alum and fugar of lead: all these colours are dyed in one and the fame copper of madder, with a heat a little below boiling a boiling heat would give a dark tawney or blackifh hue to the red, and therefore in this procefs muft neceffarily be avoided; but for the fame reafon it would contribute to deepen the black, and therefore ought always to be called in aid where thread, or entire pieces of linen or cotton, are to be dyed of this colour.'