The colour that comes nearest to scar let has been produced, on silk, by first dyeing it crimson and then dyeing it '-with carthamus, and afterwards submit ting it to a yellow bath without heat. The colour thus given is very fine, but the dye of carthamus is not permanent. In Dr. Bancroft's process, the silk is soaked for two hours in a solution of tin, in the murio-sulphuric acid, after which it is wrung out and dried partially. It is then to be dyed in a bath, prepared with four parts of cochineal and three of quercitron bark. In this way a colour approaching to scarlet is obtained. To give the colour more body, the immersion may be repeat ed in the solution of tin, and in the dye ing bath ; the brightness of the scarlet is increased by the addition of carthamus. A lively rose colour is produced by omit ting the quercitron bark, and dyeing with the cochineal alone.
Of dyeing Cotton and Linen red.
To dye cotton and linen red, madder is used ; which cotton attracts more strongly than linen. The madder-red of cotton is distinguished into two kinds, the one is called simple madder-red ; the other, which is much brighter, is called Turkey, or Adrianople red.
The process used at Rouen for the simple madder-red is as follows. The cotton must be scoured, galled with one part of galls to four of cotton, and then alumed with four ounces of Roman alum to one pound of cotton, and an equal weight of water : to the solution of alum one twentieth part of a solution of soda, consisting of half a pound of soda to quart of water, must be added. When the cotton is taken out of this mordant, it is slightlywrung,with the phi and dried ; the colour is more beautiful as the dry ing is slow ; twenty pounds of cotton are usually dyed at once, but ten would be better, because when many hanks are dyed at a time it is difficult to make the colour equal. To prepare the bath for ten pounds of cotton, about two hun dred and twenty quarts of water should be heated in a copper, and when almost too hot for the hand, six pounds of good Dutch grape madder are .to be carefully dispersed through it. When it is well mixed, the cotton is to be immersed, hank by hank, on sticks. When all the cotton is in, it is to be well worked, and the hanks turned on the sticks for thrie quarters of an hour, the bath being, kept constantly at the same degree of beat, without boiling; at the end of this time the cotton is to be taken out and left on the edges of the copper, a pint of the above ley of soda is to be added to the bath, and the cotton to be put into it again, and boiled from ten to fifteen mi nutes : lastly, it is to be taken out, left to drain, wrung, washed in a stream of wa ter, and wrung on the pin a second time.
Two days afterwards the cotton re ceives a second maddering, in the pro portion of eight ounces of madder to the pound of cotton, and is worked as in the first maddening, except that no ley is added, and that well water is used for the bath : after this the cotton is left to cool, washed, wrung, and dried. M. d'Ap ligny recommends, instead of receiving two madder baths, that the cotton be alumed twice, and then dyed in a single bath only. This red is made more lively by soaking the cotton, pound by pound, in a bath of warm water, into which about a pint of the ley is poured; is then wrung and dried ; then washd in a stream of water, and spread on the grass, where the red brightens more than by any other operation.
The Turkey red possesses a degree of brightness much superior to the com mon madder red, and more powerfully resists the action of alkalies, alum, soap, and acids. The processes used in Tur key for this red are very complicated and tedious, some taking a month to perfect ; the best of them are detailed in Berthollet's treatise on the "Elements of Dyeing." Their efficacy depends chiefly on the impregnation of the cotton with animal matter, which is mostly done by fish-oil and sheeps' dung.
One of the best processes for the Adrianople red, practised in our part of the world, is that at Glasgow, introduced by M. Papillon, at the expense and at the instance of the commissioners for manufactures in Scotland, and which is as follows : A ley is prepared for 1001b. of cotton, from 100Th. of Alicant barilla, 20th. of pearl-ashes, and 1001b. of quick lime, strong enough to bear an egg. A weaker sort is also prepared, of the strength marked by two degrees of the French hydrometer, the first kind being of six degrees. (A saturated solution of common salt marks 60°, and soft water 0°, on this instrument.) The pearl-ashes are dissolved in ten pails of soft-water, of four gallons each, and the lime in four teen pads; the liquors are let to stand till quite clear, and then ten pails of each are mixed together. In this the cotton is boiled five hours, washed in running-water, and dried ; it is then sub mitted to what is called the grey bath.