The Dyeing of Cotton Fabrics Part 19

_Scarlet._--Dye with 3 lb. Brilliant Congo R, 3 lb. soda and 20 lb.

Glauber's salt, then top with 8 oz. Safranine.

_Bright Green._--Dye with 3 lb. Chrysamine G, 2 lb. soap and 10 lb.

phosphate of soda, topping with 3/4 lb. Malachite green.

_Bright Violet._--Dye with 1-1/2 lb. Chicago blue 6 B, 1 lb. soda and 20 lb. Glauber's salt, topping with 10 oz. Methyl violet B.

_Dark Green._--Dye with 2 lb. Columbia green, 3 lb. soda and 10 lb.

Glauber's salt, topping with 10 oz. Malachite green.

_Claret._--Prepare a dye-bath with 3/4 oz. Diamine black R O, 2-1/2 lb.

Benzo purpurine 6 B, 10 lb. Glauber's salt. Dye at the boil for one hour, then enter in a fresh cold bath of 1/2 lb. Safranine G. Work for twenty minutes, lift, wash and dry.

_Seal Brown._--Make up a dye-bath with 2 lb. Benzo azurine G, 20 lb.

Glauber's salt. Enter yarn at 180 F., dye at the boil for one hour, lift, wring, and enter into a fresh bath of 1-1/2 lb. Bismarck brown.

Work for one hour at about 180 F., lift, rinse well and dry.

(6) DYEING ON TANNIC MORDANT.

The oldest group of coal-tar dyes are the basic dyes, of which Magenta, Brilliant green, Chrysoidine, Bismarck brown, Auramine are typical representatives. For a long time these dyes were only used for dyeing wool and silk; for cotton, linen, and some other vegetable fibres they have little or no affinity, and hence cannot dye them direct. However, it was found out that if the cotton be prepared or mordanted (as it is called) with tannic acid or with any substance containing that compound they could be used for dyeing cotton.

The mordant used, tannic acid, has the property of combining with the dyes of this group to form insoluble coloured tannates. Now tannic acid has a certain amount of affinity for cotton, if the latter be immersed in solution of tannic acid or any material containing it some of the latter is taken up and more or less fixed by the cotton fibre. Tannic acid is a vegetable product found in a large number of plants, and plant products, such as sumac, myrabolams, divi-divi, galls, oak bark, gambier, cutch, algarobilla, valonia, etc., which are commonly known as tannins, or tannin matters, on account of their use in the conversion of animal skins or hides into leather, which is done in the tanning industry.

By itself the tannin-colour lake, which may be formed on the cotton fibre by immersion first in a bath of tannin and then in a dye-bath, is not fast to was.h.i.+ng and soaping, but by taking advantage of the fact with such metals as tin, iron, antimony, etc., it combines to form insoluble tannates; the tannic acid can be fixed on the cotton by immersion in a bath containing such fixing salts as tartar emetic, tin crystals, copperas, antimony fluoride, and antimony oxalate. The dyeing of cotton with the basic colours therefore resolves itself into three operations:--

(1) Tanning with tannic acid or some tanning matters.

(2) Fixation with tartar emetic or other fixing agent.

(3) Dyeing with the required colour or mixture of colours.

(1) =The Tanning Operation.=--The practice of tanning or mordanting cotton with tannin is variously carried on by dyers. Some steep the cotton in the tannin bath over night, others immerse it from two to three hours in a lukewarm bath, while some enter it in a boiling bath, which is then allowed to cool down and the cotton is lifted out. The last is perhaps the quickest method, and experiments have shown that it is as good as any other method, if the quant.i.ty of tannic acid taken up be regarded as the criterion of success.

In the natural products which have just been enumerated, the tannic acid is accompanied by some colouring matter, which is also absorbed by the cotton; in some (sumac and galls) this colour is present in but small quant.i.ties; in others (divi-divi, myrabolams, algarobilla), there is a large quant.i.ty; therefore cotton treated with these comes out more or less coloured. Now it is obvious that such forms of tannin cannot be used when light tints are to be dyed, for such the acid itself must be used, for medium shades sumac or galls may be used; while when dark shades--browns, maroons, dark greens, navy blues, etc., are to be dyed, then such tannin matters as divi-divi or myrabolams may be conveniently and economically adopted. The quant.i.ty used varies according to circ.u.mstances; the character of the shades that are to be dyed, the dye-stuff used, the quality and character of the tannin matter used. For pale shades about 1 per cent. of tannic acid may be used, deep shades require from 3 to 4 per cent. Of tannin matters from 5 per cent. may be used for pale shades, from 20 to 25 per cent. for deep shades. The tannin baths are not exhausted, and may be kept standing, adding for each succeeding lot of cotton from 1/2 to 3/4 of the above quant.i.ties of tannin matters. Of course sooner or later the baths become unusable from various causes, and then they may be thrown away; but old tannin baths often work better than the new ones.

(2) =The Fixing Bath.=--Following on the tannin bath comes the fixing bath to fix the tannin on the cotton in the form of insoluble metallic tannates. A variety of metallic salts may be used for this purpose, those of antimony, tin, iron, lead, etc., the substances most commonly used being tartar emetic, antimony fluoride, oxalate of antimony, tin crystals and copperas.

Beyond forming the insoluble tannate of antimony or tin, as the case may be, the salts of antimony and tin have no further effect on the tanned cotton, and they may be used to fix the tannin for all tints or shades, from very pale to very deep. Of all these salts tartar emetic has been found to be the best, probably because it is the least acid in its reactions, and therefore there is no tendency to remove any tannin from the fibre, as is the case with the other salts. Tin salt is little used for this purpose, because of its acidity, which prevents it from fixing the tannin as completely as is the case with tartar emetic.

With copperas or iron liquor the question comes up not only of the mere fixation of the tannin, but also the fact that iron forms with tannin grey to black compounds, hence cotton which has been tanned and then immersed in a bath of copperas becomes coloured grey to black, according to the quant.i.ty of the tannin matter used. The property is useful when dark shades of maroons, clarets, greens, browns, blues, etc., are to be dyed, and is frequently employed.

(3) =Dyeing.=--After the tannin and fixing operations comes the dyeing.

This is not by any means a difficult operation. It is best carried out by preparing a cold bath, entering the prepared or mordanted cotton in this and heating slowly up. It is not necessary to raise to the boil nor to maintain the dye-bath at that heat, a temperature of 180 F. being quite sufficient in dyeing with the basic colours, and the operation should last only until the colouring matter is extracted from the dye-bath. Working in this way, level uniform shades can be got.

One source of trouble in the dyeing of basic dyes, more especially with magentas, violets and greens, lies in their slight solubility and great strength. In preparing solutions of such dyes it is best to dissolve the dye-stuff by pouring boiling water over it, and stirring well until all appears to be dissolved.

This solution should be strained through a fine cloth, as any undissolved specks will be sure to fix themselves on the cloth and lead to dark spots and stains, as, owing to the weak solubility of the dye, and this being also fixed as insoluble tannate by the tannic acid on the fibre, there is no tendency for the dye to diffuse itself over the cloth, as occasionally happens in other methods of dyeing. No advantage is gained by adding to the dye-bath such substances as common salt or Glauber's salt.

Some few of the dyes, _e.g._, Soluble blue, Victoria blue, which will dye on a tannic mordant, are sulphonated compounds of the colour base.

These can be dyed in medium or light shades on to unmordanted cotton from a bath containing alum, and in the ordinary method of dyeing the addition of alum is beneficial, as tending to result in the production of deep shades. These are somewhat faster to was.h.i.+ng and soaping, which is owing to the dye-stuff combining with the alumina in the alum to form an insoluble colour lake of the sulphuric acid groups it contains.

Many recipes can be given for the dyeing of basic dyes on cotton; for the range of tints and shades of all colours that can be produced by their means is truly great. Typical recipes will be given showing what basic dyes are available and how they can be combined together. The dyer, however, who knows how to produce shades by combining one dye-stuff with another is able to get many more shades than s.p.a.ce will permit to be given here.

_Sky Blue._--Mordant with 1 lb. tannic acid and 1/2 lb. tartar emetic, then dye with 2-1/2 oz. Victoria blue B, and 1/2 oz. Turquoise blue G.

_Bright Blue._--Mordant with 2 lb. tannic acid and 1-1/2 lb. tartar emetic, then dye with 1-1/2 lb. New Victoria blue B, and 3/4 lb.

Turquoise blue G.

_Pale Green._--Mordant with 1-1/2 lb. tannic acid and 1/4 lb. tartar emetic, then dye with 1/4 oz. Brilliant green and 1/2 oz. Auramine I I.

_Bright Green._--Mordant with 1 lb. tannic acid and 1 lb. tartar emetic, then dye with 6 oz. Brilliant green and 8 oz. Auramine I I.

_Turquoise Blue._--Mordant with 2 lb. tannic acid and 1-1/2 lb. tartar emetic; dye with 1 lb. Turquoise blue G.

_Crimson._--Mordant with 3 lb. tannic acid and 2 lb. tartar emetic, then dye with 1-1/4 lb. Brilliant rhoduline red B and 5 oz. Auramine I I.

_Bright Violet._--Mordant with 2 lb. tannic acid and 1 lb. tartar emetic; dye with 1-1/4 lb. Rhoduline violet and 3 oz. Methyl violet B.

_Rose Lilac._--Mordant with 2 lb. tannic acid and 1 lb. tartar emetic; dye with 3/4 lb. Rhoduline violet.

_Yellow._--Mordant with 3 lb. tannic acid and 2-1/2 lb. tartar emetic; dye with 2 lb. Auramine I I.

_Orange._--Mordant with 3 lb. tannic acid and 2-1/4 lb. tartar emetic; dye with 2 lb. Chrysoidine.

_Green._--Mordant with 3 lb. tannic acid and 2-1/2 lb. tartar emetic, then dye with 2 lb. Brilliant green.

_Red Violet._--Mordant with 1-1/2 lb. tannic acid and 1-1/4 lb. tartar emetic, then dye with 8 oz. Methyl violet 4 R.

The same method may be followed with all the brands of Methyl, Paris and Hoffmann violets, and so a range of shades from a purple to a pure violet can be dyed. The 4 R to R brands of these violets dye reddish shades, the redness decreasing according to the mark, the B to 6 B brands dye bluish shades, the blueness increasing till the 6 B brand dyes a very blue shade of violet.

_Bright Sea-Green._--Mordant with 1 lb. tannic acid and 1/2 lb. tartar emetic, then dye with 2 oz. Turquoise blue G and 1/4 oz. New Victoria blue B. With these two blues a very great variety of tints and shades of blue can be dyed.

_Sea Green._--Mordant with 1 lb. tannic acid and 3/4 lb. tartar emetic, and dye with 2 oz. Malachite green.

_Dark Green._--Mordant with 3 lb. tannic acid and 2 lb. tartar emetic, then dye with 1-1/4 lb. Malachite green and 3/4 oz. Auramine I I.

By combination of Brilliant green or Malachite green (which are the princ.i.p.al basic greens) with Auramine in various proportions a great range of greens of all tints and shades, from pale to deep and from very yellow to very green tints, can be dyed.

_Scarlet._--Mordant with 3 lb. tannic acid and 2 lb. tartar emetic, then dye with 1-1/2 lb. Rhodamine 6 G and 1/4 lb. Auramine I I.

_Pink._--Mordant with 1 lb. tannic acid and 3/4 lb. tartar emetic, and dye with 1/4 lb. Rhodamine G.

_Pink._--Mordant with 1 lb. tannic acid and 3/4 lb. tartar emetic, and dye with 1/2 lb. Irisamine G.

_Slate Blue._--Mordant with 1-1/2 lb. tannic acid and 1 lb. tartar emetic, then dye with 3/4 lb. Victoria blue B and 2 oz. Malachite green.

_Indigo Blue._--Mordant with 3 lb. tannic acid and 2-1/2 lb. tartar emetic, then dye with 1 lb. Methylene blue 2 B and 1/2 lb. Malachite green.

_Dark Scarlet._--Mordant with 3 lb. tannic acid and 2-1/2 lb. tartar emetic, then dye with 1 lb. Safranine prima and 1/2 lb. Auramine I I.