The Dyeing of Cotton Fabrics Part 12

_Grey._--Prepare the dye-bath with 1/2 lb. Diamine grey G, 1/2 oz.

Diamine scarlet B, 1 lb. soda, 1 lb. soap, 5 lb. Glauber's salt. Dye for one hour at the boil.

_Light Grey._--Prepare the dye-bath with 1 lb. Diamine grey G, 1 lb.

soda, 1 lb. soap, 5 lb. Glauber's salt. Dye for one hour at the boil; lift, rinse and dry.

It may be convenient here to deal with the question of the fastness of the direct dyes to such influences as light, air, acids, alkalies, washing and soaping, that have a very material influence on the use of these dyes in dyeing various fabrics. This matter can only be dealt with here in very general terms, for s.p.a.ce is limited and the dyes are too numerous for detailed mention. They vary very greatly in degrees of fastness, some are absolutely fast to all influences; the blacks are among the fastest, generally these resist washing and soaping, stand acids well and are fast to alkalies, light however affects them more or less, though they cannot be reckoned fugitive colours. The few direct greens known are good colours; they stand washing, soaping and light well, but they are affected by acids and alkalies. The blues vary very much, generally they stand soaping and have a fair degree of fastness to light, acids have but little action, alkalies tend to redden the shade, while heat also affects them. The direct browns are very variable; they are in general not fast to light; they stand washing and soaping and resist alkalies, but are altered by acids slightly. The yellows rank among the fastest of colours to light and washing and soaping; acids have but little effect; they are reddened by alkalies. Among the reds there is great variation in properties, generally they are not fast to light, standing washing and soaping well and resisting weak alkalies; some of them, such as the Benzo purpurines and Congo reds are very sensitive to acids, being turned blue with very weak acids, but on washing or soaping the original colour comes back; others, like the t.i.tan reds, Diamine reds and Delta purpurines are not so sensitive, but these are affected by moderately strong acids; there are one or two reds like Benzo fast scarlet 4 B S and Purpuramine D H, which are fast to acids. The depth of shade which is dyed has some considerable influence on the degree of fastness, the deeper shades of a colour are always faster than the paler shades, particularly as regards light, a difference of 1/2 per cent, of dye-stuff has been known to make a very appreciable degree of difference as regards the fastness of a colour to light.

In dyeing cotton with all the direct dyes, it is found that the whole of the dye-stuff is not removed from the dye-bath, how much is taken up by the cotton, and the depth of the shade which is dyed upon the cotton chiefly depends upon three factors:--

(1) Volume of water used.

(2) Quant.i.ty of saline salts used.

(3) Degree of affinity of the dye-stuff for the fibre.

There may also be some minor factors such as temperature at which the dyeing is carried on, the character and condition of the fabrics being dyed, etc.

The volume of water used in making the dye-bath has a very great influence upon the amount of dye taken up by the cotton, the greater the volume of water the less dye is absorbed and the paler the colour which is produced upon the fibre. It is therefore important to use as little water as possible in making up the dye-bath, indeed, for anything like good results to be obtained with some dyes, especially those of the sulphur series like Vidal black, Immedial blacks, Katigen browns, Cross-dye blacks, Amidazol blacks, etc., it is necessary to employ what is called a short bath, that is making it as strong as possible. The proportion of water with such dyes should not exceed fifteen times the weight of the cotton being dyed, that is, for every pound of cotton, 1-1/2 gallons of water can be allowed. This will suit the dyeing of yarns and loose fabrics like knitted stockings and hosiery goods very well. In the case of dyeing piece goods on a jigger or continuous dyeing machines even stronger liquors can be used with advantage. With some of the older, direct dyes like Congo red, Benzo azurine, Diamine scarlets, the proportion of water may be increased to twenty times the weight of the cotton. In any case the quant.i.ty of water used should not exceed twenty-five times the weight of the cotton.

The second factor, the quant.i.ty of saline salts, like Glauber's salt, soda, borax, etc., added in the dyeing, is not without influence, generally the more that is added the more dye there is left in the bath, but here again much depends upon the salt and the colouring matters used. Some salts, more particularly Glauber's salt and common salt, tend to throw some dye-stuffs out of the bath, and so the more there is used of them the deeper the shade produced on the fabric. It is quite impossible, having regard to the scope of this book, to deal with this question in detail. The dyer should ascertain for himself the best salts and the best proportions of these to use with the particular dyes he is using. The recipes given above will give him some ideas on this point.

The third factor, the degree of affinity of the dye for the cotton fibre, has some influence on the depth of shade which can be dyed from any given strength of the dye-bath. There is a very considerable difference among the direct dyes in this respect. There are some which have a fair degree of affinity, while there are others which have but little affinity, and while in the former case there is little dye left in the bath, in the latter case there is a good deal. When dyeing plain shades with single dye-stuffs this is not of much moment, because if the bath be kept for further use, as will be spoken of presently, the bath may be brought up to its original strength by adding a proportionate amount of dye-stuff, but when compound shades are being dyed, using two or more dyes, then this feature has some influence, for they will not be absorbed by the fibre in the same proportion as they were put in the bath, and so when making up the dye-bath for the second lot, and adding the same proportion of dyes, the shade which is produced will not be quite the same, for the first lot of cotton in taking up the dyes in varying quant.i.ties has altered their relative proportions, and so the bath for the second lot of cotton will actually contain more of one dye than did the first bath, and the influence of this excess of the one const.i.tuent will show itself in the shade ultimately dyed. The more lots of cotton there are dyed in the bath the greater will this influence be.

The dyer must by practical experience find out for himself in what direction this feature of the direct dyes exerts its influence on the particular dyes he is working with and make due allowance.

It is found in practice that from one-fourth to one-half of the original weight of dye-stuff is left in the bath, and in order to be as economical as possible a custom has arisen of keeping the bath and using it again for dyeing further lots of cotton. In thus making a continuous use of dye-baths it is important in preparing the baths for the next lot of cotton to add first the requisite quant.i.ties of dye-stuffs, how much will depend upon the factors and conditions already detailed, but from one-half to three-fourths of the original quant.i.ties are added.

Practical experience alone is the guide to be followed.

Having added the dye-stuff, then sufficient water must be added to bring up the volume of the bath to the proper amount, for it will have lost some. The loss of water arises from two sources: first there is the evaporation, which always occurs when dye-baths are heated up, and, second, there is the mechanical loss due to its absorption by the material which is being dyed. When a piece of cotton or other textile fabric is immersed in a dye liquor it absorbs mechanically some of it, and this amount may be roughly put down as about its own weight; thus 100 lb. weight of cotton will take up 10 gallons of liquor and carry that quant.i.ty out of the bath. To some extent this may be minimised by a previous wetting out of the cotton, which will then have in it as much liquor as it will take up, and so practically no more will be taken up from the dye-bath. Any loss of volume which may thus occur can be remedied by the addition of water.

The dye-baths containing in solution, in addition to the dye-stuff, salt, or Glauber's salt, or any other added substance, the cotton in taking up the dye liquor will of course take up some of these in proportion to the volume of liquor absorbed. The amount may range from 4 oz. to 1 lb. per gallon of liquor, and if 100 lb. cotton is being dyed and takes up from 10 to 15 gallons of liquor, it is obvious that it must absorb from 3 to 10 lb. of saline matter, and as the salinity of the dye liquor is of some importance in dyeing direct colours, in making up the bath for the next lot of cotton this must be allowed for and suitable additions made. In order to do this properly it is a good plan to rely upon the Twaddell.

The dyer should take the Twaddell of his bath before use and always make up his baths to that strength. This will be found to range from 3 to 12 Tw.

Thus, for instance, a dye-bath made from 120 gallons of water with 20 lb. to 25 lb. common salt or Glauber's salt with the dye-stuffs will stand at 4 Tw., one made with 50 lb. common salt or Glauber's salt at 8 Tw., while one which is made with 80 lb. to 100 lb. salt will stand at 12 to 13 Tw. If the dyer always maintains his liquors at one uniform degree Twaddell he can invariably depend upon getting uniform shades from his dye-baths. This uniform strength is attained by adding more salt or more water as the case may require.

Of course the continuous working of dye-baths cannot go on for ever; sooner or later the baths become thick and dirty, and then they must be thrown away and a new bath started.

(2) DIRECT DYEING FOLLOWED BY FIXATION WITH METALLIC SALTS.

It is an acknowledged principle in dyeing that to produce colours fast to washing, soaping and rubbing, there must be produced on the fibre an insoluble coloured substance. Now as the direct dyes do not essentially produce such insoluble bodies when dyed on the cotton, the colours they form are not always fast to washing and soaping. It has been ascertained, however, that some of the direct dyes, _e.g._, Benzo azurine, Chicago blue, Catechu browns, Diamine blues, Diamine browns, etc., are capable of uniting with metallic bodies to form insoluble colour lakes, and this combination can take place on the fibre. Fast shades may be dyed with the dye-stuffs named above, and with others of this group, by first dyeing them in the usual way, then pa.s.sing through a boiling bath containing bichromate of potash or copper sulphate, either together or separately. The two fixing agents here named have been found to be the best, although others, as, for instance, zinc sulphate, chromium fluoride and iron sulphate have been tried. With some dyes there is little or no alteration in shade, but in others there is some change, thus the blues as a rule tend to become greener in tone, and browns also tend to acquire a greener tone and deeper shade. The treated shades thus obtained are notable for considerable fastness to washing, soaping and light. It is to be noted that bichromate of potash exercises both a fixing and an oxidising action on dye-stuffs, hence it is needful to use it with some degree of caution and not in too great an amount, otherwise with some dyes there is a risk of over-oxidation, and in consequence poor shades will be developed. The following recipes will serve to show what dyes may thus be used, and the colours that can be obtained with them.

_Dark Red._--Use in the dye-bath 3 lb. Diamine fast red F, 3 lb. soda and 20 lb. Glauber's salt, work at the boil for one hour, then lift, rinse and pa.s.s into a boiling bath containing 3 lb. fluoride of chromium for ten to fifteen minutes, then lift, rinse and dry. By using 1 lb. of the dye-stuff in the same way a light red shade is got.

_Orange._--Dye at the boil for one hour with 1 lb. Chrysamine G, 3 lb.

soap and 10 lb. Glauber's salt, then rinse and fix in a fresh boiling bath with 1 lb. bichromate of potash, 3 lb. sulphate of copper and 2 lb.

acetic acid.

_Yellow._--Dye with 3-1/2 lb. Diamine yellow N, 3 lb. soap and 15 lb.

phosphate of soda, then fix with 4 lb. fluoride of chromium.

_Gold Yellow._--Prepare the dye-bath with 3 lb. Benzo chrome brown 5 G, 1 lb. soda ash, 12 lb. Glauber's salt. Dye at the boil for one hour and rinse. This gives an orange brown. To get the yellow shade, afterwards chrome with 3 lb. bichromate of potash, 3 lb. sulphate of copper, 1 lb.

acetic acid, in a fresh bath. Enter at about 130 F., bring to the boil, and boil for half an hour.

_Pale Leaf Green._--Dye with 3 lb. Dianil yellow 3 G, 1 lb. Dianil yellow R, 1 lb. Dianil blue G, and 20 lb. salt, then fix with 3 lb.

copper sulphate and 2 lb. acetic acid.

_Leaf Green._--Dye with 3 lb. Dianil yellow 3 G, 3 lb. Dianil blue G, and 20 lb. salt, fixing with 4 lb. copper sulphate and 2 lb. acetic acid.

_Dark Green._--Dye with 2 lb. Dianil yellow R, 1-1/2 lb. Dianil dark blue R, 1 lb. soda and 20 lb. salt, fixing with 3 lb. copper sulphate.

_Pale Olive Green._--Dye with 2-3/4 lb. Diamine fast yellow B, 1-1/4 lb.

Diamine blue R W, 3/4 lb. Diamine blue R W, 3/4 lb. Diamine catechine G; fix with 4 lb. sulphate of copper and 2 lb. acetic acid.

_Russia Green._--Dye with 2-1/2 lb. Diamine blue R W, 10 oz. Diamine dark blue B, 2-1/2 lb. Diamine fast yellow B, 3 lb. soda and 20 lb.

Glauber's salt; fix with 4 lb. sulphate of copper and 2 lb. acetic acid.

_Blue Green._--Dye with 1-3/4 lb. Diamine sky blue F F, 6 oz. Diamine fast yellow B, 1 lb. soda and 10 lb. Glauber's salt; fix with 2 lb.

sulphate of copper and 1 lb. acetic acid.

_Bronze Green._--Use in the bath at the boil 4 lb. Diamine bronze G, 2 lb. soda and 10 lb. Glauber's salt, then fix with 4 lb. fluoride of chromium.

_Pea Green._--Dye in a boiling bath with 1/2 lb. Diamine sky blue F F, 2-1/4 lb. Diamine fast yellow A, 1 lb. soda and 10 lb. Glauber's salt, then fix in a fresh bath with 2 lb. sulphate of copper and 1 lb. acetic acid.

_Leaf Green._--Dye at the boil for one hour in a bath containing 2-3/4 lb. Diamine fast yellow B, 1-3/4 lb. Diamine blue R W, 7 oz. Diamine catechine B, 2 lb. soda and 20 lb. Glauber's salt, then fix in a new bath with 4 lb. sulphate of copper and 2 lb. acetic acid.

_Light Green._--Prepare the dye-bath with 7-1/4 oz. Diamine blue R W, 5-1/2 oz. Diamine orange B, 2 lb. Diamine fast yellow B, 1 lb. soda and 10 lb. Glauber's salt, work at the boil for one hour, then treat in a fresh bath with 3 lb. sulphate of copper.

_Olive Green._--Dye with 2-1/4 lb. Chicago blue R W, 15 oz. Chrysamine G, 2 lb. soda and 10 lb. Glauber's salt; fix with 1 lb. bichromate of potash, 3 lb. sulphate of copper and 2 lb. acetic acid.

_Pea Green._--Use in the dye-bath 3 lb. Chrysophenine G, 1 lb. Chicago blue 6 B, 2 lb. soda and 10 lb. Glauber's salt, working at the boil for one hour, then fix in a fresh boiling bath with 3 lb. sulphate of copper and 2 lb. acetic acid.

_Green._--Dye with 2-3/4 lb. Chicago blue 6 B, 5 oz. Chrysamine G, 2 lb.

soap and 20 lb. Glauber's salt; fix with 1 lb. bichromate of potash, 3 lb. sulphate of copper and 2 lb. acetic acid.

_Dark Green._--Dye with 1-1/2 lb. Diamine green B, 1-1/2 oz. Diamine bronze G, 1 lb. Diamine fast yellow A, 3 lb. soda and 20 lb. Glauber's salt, working at the boil for one hour, then lift, rinse and fix in a fresh boiling bath with 3 lb. fluoride of chromium for one to fifteen minutes.

_Dark Bronze._--Use in the dye-bath 2-1/2 lb. Diamine bronze G, 3 lb.

soda and 20 lb. Glauber's salt, working at the boil for one hour, then lift, rinse and fix with 3 lb. fluoride of chromium as above.

_Dark Blue._--Prepare the dye-bath with 3 lb. Benzo blue R W, 10 lb.

Glauber's salt; dye for one hour at the boil, then treat in fresh bath with 1 lb. sulphate of copper at the boil for half an hour.

_Blue._--Dye with 1-3/4 lb. Diamine brilliant blue G, 1-1/4 lb. Diamine sky blue F F, 2 lb. soda and 20 lb. Glauber's salt; fix in a bath with 4 lb. sulphate of copper and 2 lb. acetic acid.

_Light Navy._--Dye with 1 lb. Diamine blue 3 R, 2-1/4 lb. Diamine blue R W, 2 lb. soda and 20 lb. Glauber's salt; fix with 4 lb. sulphate of copper and 20 lb. acetic acid.

_Bright Navy._--Dye with 4 lb. Diamine brilliant blue G, 2 lb. soda and 20 lb. Glauber's salt; fix with 4 lb. sulphate of copper and 2 lb.

acetic acid.