Page:Cyclopaedia, Chambers - Supplement, Volume 1.djvu/631

 DYE

fome plants tinged the paper with colours the fame with thofe they naturally poffefs, and others with different ones; and that many plants in drying aflumed a colour which was not natural to them. Alkanet, woad, the feveral forts of galli- um, and fome of the fpecies anonis, tinge the papers between which they are dried to a yellowifh. or reddifh colour, becaufe their ftalks, or fome oiher part of them, are of that colour. The common ros folis, or fun dew, whofe leaves are red, tinges the paper red alfo ; and the ros foils of Portugal diffufes this tinge through three or four meets of paper. The alpine veronica, though green in itfelf, leaves its mark in red upon the paper; and many of the common leguminous plants al- ways become black in the drying. The common mercury, which is green while growing, becomes blue in the drying; and turnefol has the fame change, though it is white in its natural ftate.

One great reafon of thefe changes of colour is, that all paper is impregnated with alum ; and this fait may very eafily ex- tract, or even alter the colours of plants, whofe juices it re- ceives; and in fuch cafes, where the alum is not in fuflicient quantity to do this, it is no wonder that it fhould however fo far affect the leaves as to turn them black. On this principle Mr. Juflieu attempted, by means of alum, to feparate colours from feveral plants, not known or ufed at prefent among the dyers, which might prove ferviceable to them. The firft experiments made on this occafion pro- ved, that there were many plants not ufed at prefent, which afford colours not at all inferior to thofe in common ufe. The experiments the fame gentleman tried on the drugs ufed for dyeing in the Indies, proved very plainly that they were no way fuperior in many cafes to vegetables of our own growth ; and that in order to have the moft lively colours from fuch fubftances, it is always neceflary to have recourfe to fome fait.

Among the other drugs ufed abroad in dyeing, there were fent over to France, on this occafion, certain yellow flowers of the radiated kind, which afforded on trial a very beautiful yellow dye ; and Mr. Juflieu found, on trying parallel experiments, that there were alfo yellow flowers in Europe of a like radia- ted kind, which were capable of affording a like beautiful yellow dye.

The flower which Mr. Juflieu tried thefe experiments upon, was the common yellow corn marygold, the chryfanthemum fegetum of Lobell. This plant flowers in the middle of July, and Mr. Juflieu drying its flowers between papers at that time of the year, found that they did not lofe their colour, as moft others do in the operation, but became of a deeper yellow than be- fore. Hence it was eafy to judge, that this flower contained a matter proper for colouring ; and decoctions being made of it of different ftrength, cloths of different kinds dipped into them became tinged to a light pale yellow, and kept this colour after being boiled in fair water. A little alum was after this added to the decoctions, and cloths dipped in thefe became much more finely dfd 3 the colour being greatly ftronger and more lively. They alfo imbibed the colour much more fpeedily from thefe decoctions ; and on boiling afterwards in water, they loft no part of it, but remained as ftrongly and as lively tinged as before. This experiment was afterwards tried by a dyer, under whofe hands it fucceeded much better than before with Juflieu, who was unacquainted with the regular methods of the trade. The decoction of the flowers gave a fort of ful- phur colour; but linnen, woolen, and filken things, which had been the day before fteeped in alum water, received from this decoction a very beautiful and fufficiently ftrong yellow. Another decoction of the flowers made ftronger than the firft, tinged a woollen cloth to a greenifti lemon colour ; and the fame decoction gave a bright gold yellow to filk : and a piece of woollen cloth, before dyed blue with indigo, on dip- ping it in this decoction became of a beautiful deep green. A fmall quantity of chimney-foot added to the decoction made it tinge cloth to a yellowifh brown ; and a fmall quantity of roucou added to the Ample decoction produced an olive yel- low.

The mixture of feveral other drugs ufed to be added to the decoctions of the common luteola or dyer's weed to vary its tinge, produced the fame changes with the decoction of this flower, and abundantly teftify'd its value and ufe in the dyeing trade. Mem. Acad. Par. 1724.

There is great reafon to believe, that the art of dyeing might be carry'd to much greater perfection than it is at prefent, if the attempts to improve it were in proper hands, and the perfons employ'd in it could be enabled to fet out with all the know- ledge there is at prefent in regard to its feveral materials, and their manner of ufe, as a fund of real facts on which to ground future difcoveries. This however feems difficult to be brought about, for the people who exercife the art generally are acquainted only with a certain fet of rules, which though they know not why they follow, yet they will not depart from them, and efteem every thing lofs of time that can be pro- pofed to them as improvements. They keep their knowledge alfo a clofe fecret from thofe who might be expected to im- prove upon it ; and ufually one man trades only in fame Sup pl. Vol. I.

DYE

one part of it without any knowledge of the reft. Hence the difficulties attending the acquiring a knowledge of the firft principles ot the art are very diicouraging, hut they are not unfurmountable. The idea which prefents itfelf moft natu- rally to us, as to the manner in which (tufts are elf J, is, that the colouring particles which fwim in the liquor, immediately attach themfelves to the furface of the body that is plunged into it, and there adhere in fo firm a manner, that there" is no removing many of them without wholly taking off the furface of the body. The barely plunging a white lubftance into a coloured liquor is not however fufficient for the dyeing It in many cales. Indeed there are only a few colours which will ftrike with this eafe and facility ; and the others require that the matter to be dfd mould have firft received the par- ticles of another fluid, whicll is in moft cafes a folution of alum and tartar in common water. And, according to the nature of the colour that is to be given the fluff afterwards, the alum is put in in large quantities, or the Huff boiled in the liquor a longer or a fhorter time. After boiling in this li- quor, a fluff is in the proper condition to receive the greater part of the common colours : but for blue, fluffs require no preparation at all ; and for fcarlet, the liquor in which they are firft boiled is made without alum.

The matter of the fluff to be dfd makes it neceflary alfo to change the liquor in which it is to be boiled, or to vafy the ingredients; and the greateft naturalift, without a mechanical knowledge of dyeing, would be amazed to fee, that if a skain of white wool, and another of white cotton, be plunged to- gether into the fcarlet efye, and this even after they have both received the fame previous boiling and preparation, the skain of cotton would come out of the liquor as white as it was put in, while the wool comes out tinged to a beautiful fire colour. The dyer however fees this every day without any admira- tion of the caufe, and never troubling his thoughts about how it is done. He ufes it daily to dye any thing woollen to a fcar- let colour, leaving a part white : in order to which, he knows there requires no more than that the part to be left white fhould be of cotton.

Mr. Dufay fuppoling this to be owing to the cotton's imbibing much more fiowiy than the wool, the liquor in which they are both previoufly boiled to make them receive the colour, as cotton is well known not to take wet fo foon as wool, ordered a fort of cloth to be wove, the warp of which was wool, and the woof cotton; and fending this to the fuller's, the two fub- ftances were lb well blended together, that it became impofii- ble for the one to receive the impregnation of any liquor with- out the other. With all thefe precautions however, the whole came out of the fcarlet Dye in the fame condition as if no- thing had been done, the cotton remaining wholly white, and the wool being marked with fire colour and white ; fo that it may be efteemed a certain fair, that the colour of cochineal cannot be given to cotton by the means of acids ; the fame alfo holds good of kermes and gumm-lac, both which are ufed inftead of cochineal to dye in fcarlet ; but neither of thefe, any more than the cochineal, will dye cotton. It is not to be concluded from hence however, that cotton cannot be dfd fcarlet by thefe fubftances; the whole is, that it requires a different treatment ; and as wool, to take the fcarlet dye, re- quires only to be firft impregnated with tartar ; cotton requires to be firft impregnated with alum, as wool does, for the Gene- rality of the other colours. The acid of fea-filt, of vitriol, vinegar and verjuice, all ferve to dye wool to a fcarlet with cochineal, but none of thefe will make it give any tin tt e to cotton, to which alum alone can ferve.

The fame Dye will give very different colours to the different parts of a cloth, which have been differently prepared. And this gentleman fhewed before the academy a piece of cloth, which he had carefully prepared in a different manner in the different parts, which being all plunged together into the Dve, when taken out and dry'd was found to be of a dirty red in that part where it had not been impregnated with any thing ; and in the other parts, where it had been differently impreg- nated, was found of all the degrees of red, from a pale da- mask rofe colour to the deeper! fcarlet, and this while it had in every part been dipt an equal time in the fame Dye. This equally holds good of the other colours. And in thefe experiments the dirty colours given to fuch parts of the cloth as have received no previous impregnation, will be wafhed away and quite carried off, while the others remain in all their per- fection.

Another circumftance very worthy attention in the dyeing of fcarlet is this, that the Dye is evidently compofed of a clear or common water, in which the colouring panicles are fufpended, and from which it is eafy to fuppofe that they are feparated and applied to the fluff in dyeing. As this is naturally fuppofed to be the cafe in regard to all colours ; (o it appears very evi- dently to be a facit in this, fince the colouring particles ad- here in fuch quantities to the matter, and feparate themfelves fo readily and perfectly from the water, that after an hour and half's boiling of the Dye with a proper quantity of the fluff in it, the whole colour'd matter ttiall be attached to the fluff, and the remaining liquor be only clear water; and what 9 N might