| BLUE NO. 1. | ||||
| Indigo carmine | 400 | grammes. | ||
| Alum | 100 | „ | ||
| Oxalic acid | 150 | „ | ||
| Boiling water | 1¼ | litre | ||
| Gum water prepared in proportion of 1 kilogram to the litre | 1¼ | litre | ||
| GREEN NO. 1. | ||||
| Gum water as above | 12 | litres. | ||
| Cuba lac | 12 | „ | ||
| Alum | 1 | kilogram, | 500 | grammes. |
| Oxalic acid | 2 | „ | ||
| Indigo carmine | 4 | „ | ||
| BOUILLON FOR THE GREENS AND BLUES. | ||||
| Boiling water | 12 | litres. | ||
| Alum | 600 | grammes | ||
| Oxalic acid | 750 | „ | ||
| Gum water | 12 | „ | ||
| SKY BLUE FOR WOOLLEN STUFF WITH COTTON WARP. | ||||
| First solution.—Boiling water | 4 | litres. | ||
| Cyanuret of iron and potash | 800 | grammes. | ||
| Second solution.—Boiling water | 2 | „ | ||
| Tartaric acid | 300 | „ | ||
| Third solution.—Cold water | 3 | „ | ||
| Sulphuric acid | 300 | „ | ||
| Pour in the first solution, then the second and third, agitating thecolor with a spatula after each new addition. | ||||
| The following mixture is afterwards applied to the stuff:— | ||||
| Gum water | 12 | litres. | ||
| Water | 6 | „ | ||
| Blue No. 1 for wool | 3 | „ | ||
APPLICATIONS OF INDIGO IN PRINTING COTTON FABRICS.
Before entering upon methods used in large establishments, it may not be without interest to observe the processes still used in Java for printing calicoes, which the natives prefer to any imported from Europe. In Java there are no factories, and the women in each family make and dye or print all the cotton cloths required for their own consumption. They apply by means of a brush or pencil, which they use with great skill, to the cotton tissue which they wish to cover a thin coating of wax mixed with a little resin, the wax being applied to all the parts where the design, which has been first traced upon the cloth, requires that the fabric should remain uncolored. They then immerse the stuff several times in an indigo vat until they have obtained the desired tint. The stuff is afterwards washed and dried for a new application of the wax, carefully applied with a pencil as before. The cloth is then immersed in a bath of a different color, made with madder or catechu, but always of some dye which is perfectly stable; and the operation is repeated according to the number of colors desired. By these successive applications of wax and immersions into different vats, they succeed in producing very complicated and harmonious colors, while no European goods compare with them in stability of dye.
In the European, and our own manufacture, the blue bottoms upon vegetable fibres, made by immersion in the indigo vat, are combined with white impressions, or others variously colored, by two distinct methods. Sometimes there is printed upon the cloth before dyeing in the indigo vat a preparation called a reserve or resist, which prevents the indigotine from being deposited in the places where it is applied. Sometimes, on the contrary, the indigo, which has been uniformly fixed upon the fabric, is destroyed in certain places marked out by printing upon them certain chemical agents, called discharges.
The reserves are mechanical, resisting the penetration of the dye, such as wax and pipe clay, or chemical. The last, through these acid or oxidizing properties, cause the precipitation of the indigotine before it has touched the fibre or penetrated into its pores. Such are the salts of copper and bi-chlorate of mercury. Other bodies perform the part both of mechanical and chemical reserves. The salts of zinc or alumina, for instance, which are frequently used, produce at the same time a deposit of indigo white and a gelatinous covering of hydrated oxide of zinc or aluminium. The composition of a good reserve is declared to be principally a question of good proportions of the constituent parts, varying with the strength of the vat and the intensity of the blue which is desired to be reserved. The first condition is that it hardens immediately after immersion in the vat: if it softens, on the contrary, it will cause the running of the color. In other words, the acidity of the impression should be proportionate to the strength and alkaline character of the vat. The white reserve, that most generally used, is composed of pipe clay, gum, verdigris, and sulphate of copper. The styles of work produced by dipping with reserves are generally of a cheap and low class. The system is clumsy and expensive, and is only tolerated because of the want of a method of directly applying indigo, which will yield the deepest shades.
Certain styles, formerly in great vogue, called Lapis, and forming one of the richest branches of the cotton-printing industry, are founded upon the use of reserves; and in these styles, by very simple means which we shall not attempt to describe, different colors produced from madder, catechu, &c., are produced upon the fabric so perfectly surrounded by blue that the eye cannot detect the slightest want of continuity. This fabrication has the greatest perfection in Russia. The imitation cashmere fabrics of cotton imported from that country, formerly much in fashion for dressing-gowns, are specimens of this fabrication. The great stability of the colors is a remarkable feature of these goods.
The system of resists or reserves possesses the inconveniences of not producing impressions of great firmness, and of requiring very strong vats. When the strength of the vat is partially exhausted, they may be thrown aside. These inconveniences are obviated by the system of discharges (enlevages). In this system the cloths are vat dyed of a uniform blue. The strength of the vat is of less importance, and it can be used until the indigo is quite exhausted. The means of destroying the indigo which has been fixed upon the fibre are founded on the use of active oxidizing agents, which transform the insoluble indigotine into soluble isatine. The agent generally used is chromic acid. As this acid cannot be incorporated with the thickening to be printed, as the thickening would produce oxide of chrome, the cloth is passed through a strong solution of chromate of potash, and dried in the shade. The required pattern is then printed on the cloth with a mixture whose principal elements are acids which are susceptible of setting free the chromic acid on the tissue, which then acts upon the indigo producing a white pattern. The acid generally employed for freeing the chromic acid is oxalic acid, thickened with British gum, dextrine, or starch, with the addition of pipe clay. To prevent running, nitric, sulphuric, or tartaric acid are sometimes used. [8]
By the method of discharges the white designs upon blue are brought out with a distinctness which it is impossible to obtain by resists, while the most delicate work of the graver can be exactly reproduced upon the tissue.