The Dyeing of Woollen Fabrics Part 11

_Bordeaux Red_.--Dye with 4 lb. Lanafuchsine S B, 1 oz. Orange extra, 10 lb. Glauber's salt, and 2 lb. sulphuric acid.

_Fawn Red_.--Dye with 1/4 lb. Orange G G, 3 oz. Lanafuchsine S B, 1/2 oz. Cyanole extra, 10 lb. Glauber's salt, and 2 lb. sulphuric acid.

_Salmon_.--Prepare the dye-bath with 1/4 oz. Fast Acid Violet R, 1/2 oz. Orange G, 10 lb. Glauber's salt, 1 lb. sulphuric acid. Work at the boil to shade.

The mordant reds are fairly numerous, and include both natural and artificial red dye-stuffs. The principle or property on which the application of this group of dye-stuffs to the dyeing of textile fabrics depends is that they are of an acid character and combine with metallic oxides, like those of iron, aluminium, or chromium to form insoluble coloured bodies, or "colour lakes" as they are called. The shade or tint of these colour lakes depends, firstly, upon the (p. 114) dye-stuff, and, secondly, upon the metallic oxide. Thus Alizarine with alumina gives a scarlet, with chrome a dark red, and with iron a dull violet. Alumina and chrome are the metallic mordants most commonly used in the dyeing of reds; sometimes tin is used, but never iron.

The coal-tar colour makers have placed at the service of dyers a great variety of mordant dyes, which may be cla.s.sified somewhat roughly into groups, according to their chemical composition. The first group is called phenolic colours. These contain the group, or radical OH, hydroxyl, once or oftener. It is to the presence of this group that they owe their acid character and the property of combination with metallic oxides. To this group of dye-stuffs belong such dyes as Alizarine, Alizarine Cyanine, Anthragallol, Gambine, Coerulein, and some others. The natural red dye-stuffs, Cochineal, Brazil-wood, madder, etc., probably belong to this cla.s.s.

None of these are essentially dyes of themselves, and used alone will not dye any fibre, it is only when they are brought into combination with the mordant that they will dye the wool fibre.

The next group may be called hydroxy-azo dyes, and are quite of modern introduction. They are azo dyes, one of whose const.i.tuents is a body like salicylic acid, amido-benzoic acid, dihydroxy-naphthalene-sulpho acid, which contain the group OH, hydroxyl with carboxyl COOH. The first group imparts phenolic characters, while the second gives true acid properties, and both of these acting together cause the dyes to be able to form colour lakes with metallic oxides. There is one point of difference between the two groups of dyes, the phenolic dyes are as a rule not dyes of themselves, some of them are practically free from colour, and it is only when brought into combination with the metallic oxide or mordant that they form a colour and dye a fibre. On the (p. 115) other hand the azo mordants are in general colouring matters, and can be used to dye wool without the aid of a mordant, the latter only serving to make the colour faster to light, acids, milling, etc., and it often has no material effect on the shade or tone of colour being dyed. Alizarine Yellow G G, Gambine Yellow, Anthracene Yellow, Chrome Violet, are examples of such dyes.

There are, however, some dyes (such as the Chromotrops, Azofuchsine, Anthracene Acid Browns, etc.) on which the mordant has a marked effect.

The methods adopted in practice for the application of this cla.s.s of dyes are many and varied. The mordants used are alum, alumina sulphate, acetate of chrome, chrome alum, fluoride of chrome, ferrous sulphate and tin chloride, while, in addition, along with these true mordanting materials, a.s.sistant mordants are used, such as argol, tartar, tartaric acid, lactic acid, lignorosine, oxalic acid and sulphuric acid.

The mordanting may be done either before or after the dyeing, the first plan being that commonly adopted with the phenolic colours, while the second method may be used and is the best to use with azo-mordant dyes. Sometimes the mordanting and dyeing may be done in one bath, but this method is one which leads to a loss of colouring matter and often to the production of colours which are loose to rubbing, and cannot, therefore, be recommended.

#Mordanting.#--This operation is carried out in the same way in all cases. The goods are entered into the bath at a temperature of about 150 F. The heat is raised to the boil, and is then maintained for one and a half hours, after which the mordanted wool is lifted and well rinsed, when it is ready for the dye-bath. As mordanting materials bichromate of potash and fluoride of chrome are chiefly used when chrome mordants are required, sometimes chrome alum. With these (p. 116) are used sulphuric acid, oxalic acid, cream of tartar or argol, lactic acid, etc.

Which of these are used depends entirely on the results which are to be got and the dye-stuff to be used, more particularly is this the case when bichromate of potash is the mordanting material. When sulphuric acid is used as the a.s.sistant along with the bichrome, then there is formed on the wool fibre a deposit of chromic acid and chromium oxide, and this exerts an oxidising effect on the colouring matter or dye-stuff, which in some cases, as the Alizarine Blue, Alizarine Yellow, etc., leads to a destructive effect, and, therefore, the production of weak shades, so that it is not possible always to use an oxidising mordant. When tartar, argol, oxalic acid, lactic acids and other a.s.sistants of an organic nature are used, then a different effect is obtained, the bichromate is completely decomposed, and a deposit of chromium oxide formed on the wool. This does not exert any action on the colouring matter, and hence this mordant is known as the non-oxidising mordant. It may be pointed out that when wool is mordanted with pota.s.sium or sodium bichromate and sulphuric acid (oxidising mordant) it has a deep yellow colour, while when mordanted with bichromate or other chrome salt, and the organic a.s.sistants enumerated above (non-oxidising mordant), it has a green colour, and one sign of a well-mordanted wool is when it has a good bright tone free from yellowness.

Of the organic a.s.sistants tartar is undoubtedly the best in general use, and, although slow in its action, leaves a good deposit of oxide of chrome on the wool in a suitable condition to develop the best results on dyeing. Argols are only an impure tartar. They can only be used when dark shades are to be dyed. Oxalic acid does not work as well as tartar, and there is not so much chrome oxide deposited on the wool, while there is a slight tendency for a small proportion of this to be in the form of chromic acid. Of late years lactic acid and (p. 117) lignorosine have been added to the list of a.s.sistant mordants; both these give excellent results, they lead to a more complete and more uniform decomposition of the bichromate, and therefore the mordanting baths are more completely exhausted, so that rather less bichromate is required; the shades which are obtained are in general fuller and brighter. Examples of the use of these a.s.sistants will be found among the recipes given below.

With fluoride of chrome either oxalic acid or tartar is used, and a deposit of chromium oxide is formed on the wool, the general effect being the same as when bichromate of potash is used with oxalic acid or tartar.

Alumina is applied either in the form of alum or of sulphate of alumina, argol or tartar being used as the a.s.sistant, oxide of alumina being deposited on the fibre.

When ferrous sulphate (copperas) is used then tartar is almost invariably used as the a.s.sistant mordant, oxalic acid only rarely.

The dyeing with mordant dyes must be done in a special way and with great care, if uniform, level shades and fast colours are to be obtained.

The dye-bath must be started cold, and the wool be entered and worked for twenty to thirty minutes, the object being to cause the dye-stuffs to penetrate well into the substance of the fibre, then the temperature is slowly raised to the boil, not less than three-quarters of an hour being taken in doing so; the temperature is maintained at the boil for fully one and a half hours longer. During the boiling operation the mordant and dye-stuff combine together, and form the characteristic colour lake, and the boiling fixes this firmly on to the wool.

The water used plays a very important part. If too hard in character, the lime it contains shows a tendency to combine with the (p. 118) dye-stuff and form a colour lake, which is deposited in a loose form on the wool or in the bath, tending to make the shades dull and loose to rubbing. This defect can be remedied by adding a little acetic acid to the dye-bath, say about 3 lb. to 100 gallons of the water. It combines with and neutralises the influence of the lime, in so far as the formation of a loose colour lake is concerned; still the lime does unite with the dye-stuff, but the combination is formed more slowly, and in or on the wool fibre so that it is fast.

By working in the manner laid down above very fast shades can be dyed on wool with mordant dyes, and the following recipes will give the other details as to tints, shades, quant.i.ties, etc., not noted above.

_Claret_.--Mordant, 2 lb. bichromate of potash and 2 lb. tartar; dye, 8 lb. Alizarine Claret R.

_Fawn_.--Mordant, 3 lb. bichromate of potash and 1-1/2 lb. tartar; dye, 3 lb. Alizarine Orange N.

_Maroon_.--Mordant, 3 lb. bichromate of potash and 2-1/2 lb. tartar; dye, 15 lb. Alizarine Orange N.

_Deep Crimson_.--Mordant, 3 lb. bichromate of potash and 2-1/2 lb.

tartar; dye, 8 lb. Alizarine Red 1 W S.

_Lilac Rose_.--Mordant, 1-1/2 lb. bichromate of potash and 1-1/2 lb.

tartar; dye, 1 lb. Alizarine Red 1 W S.

_Crushed Strawberry Tint_.--Mordant, 2 lb. bichromate of potash and 1-1/2 lb. tartar; dye, 3 lb. Alizarine Red 2 W S.

_Deep Claret_.--Mordant, 3 lb. bichromate of potash and 2-1/2 lb.

tartar; dye, 5 lb. Alizarine Red 1 W S.

_Bright Fawn Red_.--Mordant, 2 lb. bichromate of potash and 1-1/2 lb.

tartar; dye, 1 lb. Alizarine Red 5 W S.

_Scarlet_.--Mordant, 10 lb. alum and 6 lb. tartar; dye, 4 lb.

Alizarine Red 5 W S.

_Rose_.--Mordant, 6 lb. alum and 4 lb. tartar; dye, 1 lb. Alizarine Red 1 W S.

_Deep Scarlet_.--Mordant, 10 lb. alum and 6 lb. tartar; dye, (p. 119) 4 lb. Alizarine Red 1 W S.

_Deep Maroon_.--Mordant, 3 lb. bichromate of potash and 1 lb.

sulphuric acid; dye, 5 lb. Alizarine Red 3 W S.

_Bright Maroon_.--Mordant, 3 lb. bichromate of potash and 2 lb.

tartar; dye, 5 lb. Alizarine Red S W, 10 lb. Mordant Yellow.

_Deep Fawn Red_.--Mordant, 3 lb. bichromate of potash and 2-1/2 lb.

tartar; dye, 10 lb. Alizarine Orange W and 1 lb. Mordant Yellow.

These typical recipes are here given to show what tints may be obtained from the alizarine and the quant.i.ty of dye-stuffs required.

By using other proportions of dye-stuffs than those given a variety of other tints may be dyed.

The method of working described above is applicable to other mordant dyeing colours besides the alizarine reds, such as Alizarine Orange, Alizarine Blue, Anthracene Brown, Alizarine Cyanine, Galloflavine, Gambine, Chrome Violet, etc. It will therefore not be required to repeat this description of the process when the use of mordant colours for producing other colours, such as blues, navies, drabs, browns, etc., is dealt with.

Although the shades dyed with the alizarines and allied colouring matters are lacking in the brilliance characteristic of the azo scarlets, yet they have the very great advantage of being quite fast to washing, acids and light.

There is another method of using those alizarine reds that are sold in the form of powder, and which are distinguished by the letter S. They are of some value in dyeing heavy woollen cloths, and the method is indicated in the two recipes which follow:--

_Brilliant Scarlet_.--Prepare a dye-bath with 20 lb. Glauber's salt and 4 lb. Alizarine Red 1 W S, boil the wool in this for three-quarters of an hour; then lift, add to the same bath 4 lb. (p. 120) sulphuric acid, again work at the boil for three-quarters of an hour; then lift, add 10 lb. alum, re-enter the goods, and work three-quarters of an hour longer; then lift, wash and dry.

_Claret_.--Prepare a bath with 20 lb. Glauber's salt and 4 lb.

Alizarine Red 1 W S, boil for three-quarters of an hour; then lift, add 4 lb. sulphuric acid, re-enter the wool, boil for three-quarters of an hour; then lift, add 3 lb. bichromate of potash, re-enter the wool, and boil for three-quarters of an hour longer; then lift, wash and dry.

_Bluish Red_.--Mordant, 2 lb. bichromate of potash and 2 lb. lactic acid; dye, 2 lb. Alizarine Red S. In this recipe there is used lactic acid as the a.s.sistant, and a very fine shade results.

_Red_.--Mordant, 3 lb. lignorosine, 2 lb. bichromate of soda and 1 lb.

sulphuric acid; dye with 12 lb. Alizarine Orange 2 G.

_Dark Bordeaux Red_.--Mordant, 3 lb. lignorosine, 3 lb. bichromate of soda and 1-1/2 lb. sulphuric acid; dye, 12 lb. Alizarine S X.

_Dark Red_.--Mordant, 3 lb. lignorosine, 2-1/2 lb. bichromate of soda and 1-1/4 lb. sulphuric acid; dye, 6 lb. Alizarine Orange 2 G and 4 lb. Alizarine S X.