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

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

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

Printed For Thomas Tegg, 73, Cheapside;
R. Griffin & Co., Glasgow; Tegg and Co., Dublin; Also J. & S. A. Tegg, Sydney and Hobart Town.


Part II. The Practise of Dyeing. Of Dyeing Scarlet.
s. 608-611

184. Scarlet may be regarded as one of the compound colors arising from a mixture of the red and yellow coloring matters. Scarlet is the finest and most splendid of all the colors, and the great demand for it has excited several chemists of distinction to improve and facilitate the process of producing it. We shall here briefly notice the old method of dyeing scarlet, which is still practised by some dyers, both in this country and on the continent, and then give the improved method proposed by Dr. Bancroft in his excellent treatise already mentioned.

185. We cannot, says M. Berthollet, expect to obtain the desired shade from the doses prescribed in the processes, from variations in the quantity of the coloring particles contained in the different kinds of fine cochineal, and particularly from the solutions of tin that are used differing considerably from each other; but the just proportions of the ingredients to be employed may be readily determined by trials in the small way, so as to obtain the shade called for; and, if the pieces which are dyed be above or below this shade, it is net difficult to find the suitable proportions.

186. In the process of dyeing scarlet two operations are observed, vix. the boiling, and the reddening. The first of boiling operation is thus conducted: - For 100 pounds of cloth, a quantity of soft water is heated in a tinned boiler, till it be rather more than lukewarm, after which six pounds of cream-of-tartar are dissolved in it. When the water is a little wemer, half a pound of finely powdered cochineal is added and well mixed with the solution of tartar. Immediately after, five pounds of very clear solution of tin are poured in, and carefully mixed. When the bath begins to boil, the cloth is put in, and rapidly turned two or three times with the winch, then more slowly, and is left to boil for two hours, after which it is taken out, drained, exposed to the air, and washed in the running stream.

187. In preparing for the second bath the boiler must be emptied, filled again with fresh water, and, when this is near the boiling heat, five pounds and three quarters of powdered cochineal are put in and carefully mixed, and when, on ceasing to stir the liquor, a crust forms on the surface, and begins to break, thirteen or fourteen pounds of solution of tin are poured in. Sometimes after this, the liquor [...] above the brim of the boiler, which [...]vented by putting in some cold water. [...] the solution is well mixed in the bath, [...] is immersed, taking care to turn the [...] rapidly for the first two or three [...] then to be boiled for about an hour, [...] down as often as it rises to the surface [...] this it is taken out, exposed to the air [...] washed in the stream, and dried.

188. On examining the proportions of cochineal and of solution of tin, used [...] boiling, or in the reddening, it appears [...] are by no means fixed. There are [...] who, according to Hellot's account, [success?] well by putting two-thirds of the [...] and a fourth of the cochineal, into the [...] and the remaining third of the compo[...] the remainin three-fourths of the cochineal [...] the reddening. He also asserts that it [does / doesn't?] harm to use tartar in the reddening, [...] more of it than half the wight of the [...] he put in; and he thinks, that it even [...] the color more permanent. Some dyers [...] take the cloth out of the boiling, but [...] fresh it to make the reddening in the [...] by pouring in an infusion of cochineal. [...] they have made apart, and with which they [...] mized the proper quantity of composition. [...] this way they save time and fuel: [...] affirm that the scarlet is equally fine.

189. Different authors recommed different proportions of the materials used in the [...] process. Scheffer prescribes one part of [...] of tin for ten parts by weight of the cloth, [...] equal quantity of starch and of tartar as [...]lution. He remarks, that the starch [...] make the color more uniform, and he recommends to throw into the water, then [...] 1/32 of starch, 1/34 of solution of tin, 1/34(?) of [...] and 1/12(?) of cochineal.

It appears that Scheffer employs a much smaller quantity of solution of tin than [Hellot?] but what he does employ contains [...] tin.

190. Poerner describes three principal processes, according as the shade is to be [...]less deep, or more or less of an orange [...] which he wishes to give to the scarlet. [...] the proportions of the solution of tin, of cochineal, and tartar, or omits the last ingredient.

For conducting the process if the scarlet [...] in the most beneficial manner, and [...] its results, according to the end in view, the [...] of each of the ingredients employed in [...] be ascertained. We need not however [...] with a detail of processes which have been [su?]perseded by others that are from xpe[...] to be much superior; we shall therefore [...] to notice the important improven[...] brach of dyeing made by Dr. Bancroft [...] which have obtained the approbation of [...] eminent chemists, British and foreign.

191. Dr. Bancroft was struck with the [...] that for a whole century no improvement [...]

been made in the art of dyeing scarlet. On this subject he seems to have fixed his mind, and, about the year 1786, he instituted a set of experiments which were attended with the most gratifying success.

192. Having, by frequent affusions of boiling water, extracted the whole of the coloring matter from powdered cochineal, he found that the addition of a little potash to the sediment, and a fresh quantity of boiling water, extracyed a new proportion of coloring matter, equal to about one-eight of what had been given out to the pure water. He repeatedly extracted this coloring matter by means of potassa, and afterwards dyed small pieces of cloth scarlet with it, which he [...] similar to others dyed with cochineal. It was in the course of these enquiries that he perceived scarlet to be a compound color, consisting of about three-fourths of pure crimson, and one-fourth of pure bright yellow. He conceived, therefore, that when the natural crimson of the cochineal is made scarlet, by the usual process, there must be a change produced, equivalent to a conversion of one-fourth of the coloring matter of cochineal from its natural crimson to a yellow color. From this he concluded that there might be a great saving of cochineal, by substituting a cheaper substance, which, at the same time, might yield a better yellow color. It was therefore his object to combine with this crimson or rose color, a suitable portion of a lively golden yellow, capable of being permanently fixed, and reflected by the same basis. This yellow Dr. Bancroft found in quercitron bark; and ascertained that it possessed the advantage of being not only the cheapest, but the brightest of all the yellows he had tried.

193. For the purpose of diminishing the quantity of cochineal employed in producing a scarlet dye, Dr. Bancroft made a number of experiments under the authority of government. In these experiments, the mordant used was the common dyers' spirit, or the nitro-muriate of tin, but he found that they were not attended with the advantages which he expected. In some of his earliest experiments, he remarks, that the solution of tin by means of sulphuric acid destroys the cochineal color, and this led him to reject the use of this acid, till accident brought him to dissolve a quantity of tin in muriatic acid, combined with one-fourth of sulphuric acid. The application of this solution in dyeing, was not accompanied with the corrosive effects of the muriate and nitro-muriate which he had employed in the experiments, and which proved unsuccesful. After trying different proportions of these acids, he found the following to answer best. In a mixture of two pounds of sulphuric acid of the ordinary strenght, and about three pounds of muriatic acid, he dissolved about dourteen ounces of tin. The muriatic acid is first poured upon a quantity of granulated tin in a suitable vessel, and the sulphuric acid is added by degrees. This solution is more quickly effected by means of a sand heat; it is perfectly colorless, and may be kept for years without precipitation. It has double for the power of the common dyers' spirit; and is produced at about one-third of the expense. It also raises the colors more than even the tartrate of tin; and does not incline the cochineal crimson to the yellow shade.

194. In using this solution as a mordant, to produce a compound scarlet color, Dr. Bancroft advises the following process. Nothing, says he, is necessary, but to put the cloth, suppose 100 pounds, into a proper tin vessel, nearly filled with water, in which has been mixed eight pounds of the murio-sulphuric solution of tin; and, having brought the ixture to a boiling heat, about 100 pounds of cloth are immersed and turned through it as usual, by the winch, for a quarter of an hour. Then the coth is removed, and four pounds of cochineal and two pounds and a half of quercitron-bark, both powdered are introduced and well mixed. After this, the cloth is returned into the bath, the liquor is made to boil, and the cloth is turned as usual for fifteen or twenty minutes, by which time, in general, the color will be properly raised and the bath exhausted, when the cloth is taken out and rinsed in the ordinary way.

By this method the time, labor, and fuel, necessary for filling and heating the boiler a second time are saved, the process finished much sooner than in the common way, and there is a saving of all the tartar, as well as of two-thirds of the cost of spirit, or nitro-muriatic solution of tin, which, for dyeing 100 pounds of wool, commonly amount to ten shillings, whereas eight pounds of the murio-sulphuric solution cost only about three shillings. There is, besides, a saving of at least one-fourth of the cochineal usually employed, and the color produced does not prove inferior in any respect to that dyed with much more expense and trouble in the ordinary way.

195. When a rose color is wanted, it may be readily obtained in this way, only omitting the quercitron bark, insted of the complex method of first producing a scarlet, and then changing it to a rose by the colatile alkali contained in stale urine, set free by potash or by lime; and hould any one still choose to continue the practise of dyeing scarlet without the quercitron bark, it is only necessary to employ the usual proportions of tartar and cochineal, with a suitable quantity of the murio-sulphate of tin, which, while it is cheaper, is much more effectual than the dyeräs spirit.

196. The scarlet, produced from cochineal crimson and quercitron, is also attended with this advantage, that it may be dyed upon wool and woollen yarn, without any danger of its being changed to a crimson color by the process of fulling, which always happens to scarlet dyed in the common way. Indeed, this last is nothing but a crimson or rose color, rendered yellow by some particular action of the tartaric acid; and is hence liable to be reduced to crimson by many chemical agents, especially by soap, alkaline salts, salts of lime, &c. But where the coloring matter of cochineal is applied and fixed merely as a crimson or rose color, and is rendered scarlet by adding a very permanent yellow, capable of resisting the strongest acids and alkalis, when used with the solutions of tin, no such


chanfe takes place, because the color given by cochineal, having never ceased to be crimson, cannot be rendered more so, and therefore cannot suffer by those impressions or application which frequently change or spor scarlets dyed according to the ordinary practice. There is also a remarkable property attending the compound scarlet dyed with cochineal and quercitron bark, viz. that if a piece of cloth dyed in this way be compared with another piece dyed by the usual process, both will by day-light appear exactly of the same shade, but, if they be afterwards compared together by candle-light, the former will appear at least several shades higher and fuller than the latter; - a circumstance of some importance, when it is considered how much this and other gay colors are worn and exhibited by candle-light, during a considerable part of the year.

197. To illustrate more clearly, continues Dr. Bancroft, the effects of the murio-sulphuric solution of tin with cochineal in dyeing, I shall state a very few of my numeous experiments therewith; observing, however, that they were all several times repeated, and always with similar effects.

1st, I boiled 100 parts of woollen cloth in water, with eight parts of the murio-sulphuric solution of tin, during the space of ten or fifteen minutes; I then added to the same water four parts of cochineal, and two parts and a half of quercitron bark in powder, and boiled the cloth fifteen or twenty minutes longer; at the end of which time it had nearly imbibed all the color of the dyeing liquor, and received a very good, even, and bright scarlet. Similar cloth dyed of that color at the same time in the usual way, and with a fourth part more of cochineal, was found upon comparison to have somewhat less body than the former; the effect of the quercitron bark in the first case having been more than equal to the additional portion of cochineal employed in the latter, and made yellow by the action of tartar.

2d, To see whether the tartrite of tin would, besides yellowing the cochineal crimson, contribute to raise and exalt its color more than the murio-sulphate of that metal, I boiled 100 parts of cloth with eight parts of the mutio-sulphuric solution, and six parts of tartar, for the space of one hour; I then dyed the cloth, unrinsed in clean water, with four parts of cochineal, and two parts and a half of quercitron bark, which produced a bright aurora color, because a double portion of yellow had been here produced, first by the quercitron bark, and then by the action of tartar upon the cochineal coloring matter. To bring back this aurora to the scarlet color, by taking away or changing the yellow produced by the tartar, I divided the cloth whilst unrinsed into three equal parts, and boiled one of them a few minutes, in water slightly impregnated with potassa; another in water with a little ammoniac; and the third in water containing a very little powdered chalk, by which all the pieces became scarlet; but the two last appeared somewhat brighter than the first, the ammoniac and chalk having each rosed the cochineal color rather more advantageously than the potassa. The best of these, [...] comparison, did not seem preferable to the compound scarlet dyed without tartar, as in [...]ceding experiment; consequently this [...] seem to exalt the cochineal color more than [...] murio-sulphate of tin; had it done so, the [...] it in this way would have been easy [...] relinquishing the advantages of the [quercitron?] yellow.

3d, I boiled 100 parts of woollen cloth [...] eight parts of the murio-sulphuric [solution?] of tin, for about ten minutes, when I [added?] four parts of cochineal in powder, [...] by ten or fifteen minutes more of boiling [pro?]duced a fine crimson. This I divided [...] equal parts one of which I yellowed, or [...] scarlet by boiling it for fifteen minutes [with?] tenth of its weight of tartar in clean water. [...] the other, by boiling it for fortieth part [of its?] weight of quercitron bark, and the same [...] of murio-sulphuric solution of tin; so this last case there was an addition of [...] coloring matter from the bark, whilst in [...]mer no such addition took place, the [yellow? ne?]cessary for producing the scarlet having [...] wholly gained by a change and [...] the cochineal crimson; and the two [...] compared with each other, that which [...] rendered scarlet bu an addition of [quercitron?] yellow, was, as might have been expectyd, [...]veral shades fuller than the other.

4th, I dyed 100 parts of woollen [cloth?] scarlet, by boiling it first in water with [...] parts of murio-sulphate of tin, and twelve [parts?] of tartar, for ten minutes, and then adding [...] parts of cochineal, and cintinuing the [...] fifteen minutes. This scarlet cloth I [...] equally, and made one part crimson, by [boilin?] it with a little ammoniac in clean water [, and?] which I again rendered it scarlet, by [boiling? it? in?] clean water, wit a fortieth of its wieght of [muriatic? ...]phate of tin; and this last, being compared [...] the other half to which no quercitron yellow [has?] been applied, was found to possess much [...] color, as might have been expected. A [...] the cloth, which had been dyed scarlet by cochineal and quercitron bark, as in the first [treat?]ment, being at the same time boiled in the [...] water with ammoniac, did not become [...] like that dyed scarlet without the bark.

In this way of compunding a scarlet from cochineal and quercitron bark, the dyer [...] all times be able, with the utmost certainty, [to] produce every possible shade between the crimson and yellow colors, by only increasing [...]minishing the proportion of bark. It has [...] been usual at times, when scarlet approach [...] nearly to the aurora color were in [fashion? ...] superadd a fugitive yellow wither from [...] or from what is called young fustic; but [...] only when the cochineal color had been [pre?]viously yellowed as much as possible by the [cream?] of tartar, as in the common way of dyeing scarlet; and therefore that practise ought [...] confounded with my improvement, which [...] its object to preclude the loss of any part [...] cochineal crimson, by its conversion [...] low color, which mayt be so much [...]

obtained than the quercitron bark. By sufficient trials, I have satisfied myself that the cochineal colors, dyed with the murio-sulphuric solution of tin, are in every respect at least as durable as anu which can be dyed with anu other preparation of that metal; and they even seem to withstand the action of boiling soap lie somewhat longer, and therefore I cannot avoid earnestly recommending its use for dyeing rose and other cochineal colors, as well as for compounding a scarlet with the quercitron bark.

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