The London Encyclopædia: Part II. The Practise of Dyeing. Of Dyeing Violet Color, &c.

The London Encyclopædia: Part II. The Practise of Dyeing. Of Dyeing Violet Color, &c.


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 Violet Color, &c.
s. 618-619


247. To Dye Wool Violet, & c. - From the mixture of red and blue are obtained violet, purple (columbine), dove-color, pansy, amaranth, lilac, mallow, and a great many other shades, determined by the nature of the substances, whose red color is combined with a blue color, of which one becomes more or less predominant over the other, according to the proportions of the ingredients, and the other circumstances of the process. Hellot observes, that stuff which has been dyed scarlet, takes an unequal color when blue is to be united with it. The blue is therefore given first, which, even for violet and purple, ought not to be deeper than the shade distinguished by the name of sky-blue; a boiling is given with alum mixed with two-fifts of tartar; the stuff is then dipped in a bath composed of nearly two-thirds as much cochineal as for scarlet, to which tartar is always added.

248. The circumstance which distinguishes the process for purple from that for violet, is that for the former a lighter blue ground is given, and a larger proportion of cochineal is employed. These colors are frequently dyed after the reddening for scarlet, such quantities of cochineal and tartar being added as are necessary; the operation is managed in the same way as for scarlet. But lilacs, pigeon's necs, &c., are commonly dipped in the boiling, which has served for violet, after alum and tartar have been added to it: the blue ground having been proportioned to the shade required, the quantity of cochineal is also adjusted in a similar manner; a [... so(?)]lution of tin is added for some reddish [shade?] such as peach blossom. It is to be [observed?] that, though the quantity of cochineal is [dimi?]nished according to the lightness of the [shade?] required, the quantity of tartar is not [lesser?] so that the proportion of it, compared with [that?] of the cochineal, is so much greater, as the color required is lighter.

249. M. Poerner is of opinion, that to [perceive?] the colors composed of red and blue, it is [advan?]tageous to employ the solution of indigo [as? sul?]phuric acid, because a great variety of shades is thus more easily obtained, and the process is [not?] so long and expensive. But the colors [...] obtained are less durable than when the [...] is employed. He says, however, that they have sufficient permanence, if a solution of indigo be used to which some alkali has been added.

The effects may be easily varied, by giving [...] preparation to the stuff with different [...] of alum and tartar, or with solution of [...] by dyeing with different proportions of cochineal and solution of indigo.

250. A process for dyeing wool of a purple color is given by M. Berthollet, as having been communicated to him by Descroizilles. [...] this: - If it be wool in the fleece which is [...] dyed, one-third of its weight of mordant is required; if it be a woven stuff, only a fifth is necessary. A bath is prepared at a temperature which the hand can bear; the mordand [is well?] mixed with it; and the wool or stuff is [... im?]mersed. Its is to be properly agitated, and [...] same degree of heat is to be kept up for [...] hours, which may be ecen increased a [little? to?]wards end. It is then lifted out, aired, and very well washed. A new bath of pure water [...] the same heat is prepared; a sufficient [...] of violet wood is added to it; the stuff is then [...] down, and agitated; and the heat is urged to the boiling point, at which it is maintained for a quarter of an hour. The stuff is then [...] aired, and carefully rinsed. The dye is [...] completed. If a decoction of one pound of logwood has been used for three pounds of wool and proportionately for the stuffs which [...] a smaller dose, a beautiful violet is obtained, [...] which a sufficient quantity of Brasil-wood [...] the shade known by the name of prune de [mon?]sieur.

251. The ingenious author from whom we quote the above, thus endeavours to explain the process:-

If we may venture an opinion, without [...] made direct experiments on a complicated process, such as that communicated by Descroizilles, and which is still employed advantageously by some manufactories with modifications which we do not know, we would suggest the following explanation.

The muriate of soda is decomposed by the sulphuric acid, and the muriatic acid [...] liberty dissolves the tin.

A portion of the tin is precipitated by the [...]taric acid, whence the deposite is [...]. But a portion which remains in solution [...] to modify the effect, as we have seen with [...]

[619]

the cochineal. The oxide of copper, present in this preparation, forms blue with the coloring particles of the indigo; the oxide of tin with the same wood gives violet, and red with the coloring matter of Brasil-wood.

252. Of Dyeing Silk Violet, & c. - There are [...]ve kinds of violet colors given to silk, these are, by the French writers on dyeing, distinguished into the fine and the false. The fine violet may be given by dyeing the silk with cochineal, and afterwards passing it through the indigo vat. The preparation and dyeing of the silk with cochineal are the same as for crimson, with the mission of tartar and solution of tin, by means of which the color is heightened. The quantity of cochineal made use of is always proportioned in the required shade; but the usual proportion for a fine violet color is two ounces of cochineal for every pound of silk. When the silk is dyed, it is washed at the river, twice beetled, dipped in a vat of a strength proportioned to the depth of the violet shade, and then washed and dried with procautions similar to those which all colors require that are dyed in a vat. If the violet is to have greater strength and beauty, it is usual to pass it through the archil bath, a practice which though frequently abused, is not to be dispensed with for light shades, which would otherwise be too dull.

253. When silk has been dyed with cochineal, at above directed, a very light shade of blue must be given it for purple. Only the deepest shades are passed through a weak vat. For those which are less so, cold water is had recourse to, into which a little of the blue vat is put, because they would take too much blue in the vat itself, however weak it may be. The light shades of this color, such as pink, gridelin, and peach-blossom, are made in the same manner, with a diminution of the proportion of cochineal.

254. The spurious violets are given to silk in various ways. The most beautiful, and those most in use, are prepared with archil. The strenght of the archil bath is proportioned to the color wished for: the silk, to which a beetling in the river has been given on its coming out of the soap, is turned through it round the skein sticks. When the color is thought to be deep enough, a trial is made on a pattern in the vat, to see if it takes the violet that is wated. If it is found to be at the proper pitch, a beetling is given to the silk at the ricver, and it is passed throgh the vat as for fine violets. Less blue, or less archil, is given, according as the violet is wished to incline to red or to blue.

255. A violet color may be imparted to silks by immersing them in water impregnated with verdigris, as a substitute for aluming, and then giving them a bath of logwood, in which they assume a blue color; which is converted into a violet, either by dipping them in a weaker or stronger solution of alum, or by adding it to the bath; the alum imparts a red shade to the coloring matter of the logwood. This violet possesses but a little beauty, or permanence, but if the alumed silk be immersed in a bath of Brasilwood, and nect in a bath of archil after washing it at the river, a color is obtained possessing a much higher degree of beauty and intensity.

M. Decroizilles' process, above related, for dyeing wool, was found to succeed equally well, according to his account, in communicating a violet color to silk.


256. Of Dyeing Cotton and Linen Violet, &C. - The process in most common use for dyeing cotton and linen of the violet colors is the following: - The stuffs have first a blue ground communicated to them in the indigo vats according to the shade required; they are then dried. After this they must be galled in the proportion of three ounces of galls to a pound: they are left for twelve or fifteen hours in the gall bath, after which, they are wrung and dried again. They are then passed through a decoction of logwood; and when well soaked are taken out, and two drachms of alum, and one of dissolved verdigris, for each pound of stuff are added to the bath; the skeins are then redipped on the sticks, and turned for a full quarter of an hour, when they are taken out to be aired; after which they are again completely immersed in the bath for a quarter of an hour, then taken out and wrung. The vat which has been employed is then emptied; half of the decoction of logwood which had been reserved is poured in; two drachms of alum are added, and the stuff dipped afreh, until it is brought to the shade required. The decoction of logwood ought to be stronger or weaker according to the shade required; this violet stands the action of the air tolerably well, but is not so durable as that obtained by madder.

257. Permanent purple and violet colors may be given to cotton stuffs that have been dyed a Turkey-red, by adding to the alum steep a proportion of sulphate of iron suited to the shade required. Cotton also that has been dyed a light blue with indigo, may be changed to purple or violet by passing the stuff through a bath prepared with the aluminous mordant, and dyeing with madder.