Another process consists in printing on the thick ened mordants and then dyeing the goods. The color is fixed where the mordant has been printed.
Patterns are produced by printing dyed goods with chemicals which destroy the color. This is known as discharge work. Starches, gums, flour and other similar bodies are used in making the printing pastes. Wool, silk and yarns are also printed; the latter, however, on a machine in which the design is in relief. Both sides of the cloth may be printed in one passage through a double machine. If the patterns on both sides are to be alike and are required to fit properly, it is necessary to have the sets of rollers engraved in pairs, and in reverse order.
Home dyeing.
In all dyeing processes it is essential to have the goods free from grease, dirt and foreign mat ter, and, for light colors, they should be bleached. In home dyeing, strict attention should be paid to cleanliness of the goods, and care taken accurately to carry out dyeing instructions. The package dyes, sold everywhere, are very serviceable, though not always entirely satisfactory. It should be remem bered that the after-processes add a great deal to the appearance of the goods, and that amateurs have neither the necessary apparatus nor the skill of the professional dyer. Valuable material should be sent to a first-class dyer.
By carrying out the following tests on small samples, which can be made readily, the suitability of the material for any particular use may be as certained easily, and much after-annoyance avoided: (1) Fastness to light and atmospheric influences. The sample is exposed to sunlight under glass, and compared from time to time with a reserved part. Expose for two or more weeks; the longer the better. A more se vere test is to expose to the weather.
(2) Fastness to rub bing. Rub with a piece of white cloth.
(3) Fastness to iron ing. Press with a hot iron, and compare.
(4) Fastness to washing. Wash with hot soap four times, allowing t h e goods to dry in the air be tween each two treat ments.
(5) Fastness to al alkali. Immerse in strong ammonia and then in washing soda (one part in ten of water); dry without washing.
(6) Fastness to perspiration. Treat for one hour with a teaspoonful of 30 per cent acetic acid in a pint of water at about blood heat. White wine vinegar diluted with an equal quantity of water will answer.
(7) Fastness to boiling in soda. Boil for one hour in a gallon of water in which two ounces of wash ing soda and one-half ounce of castile soap have been dissolved.
Literature.
Georgivics, Chemistry of Dyestuffs; A. G. Green, Survey of the Organic Colouring Matters ; Allen, Commercial Organic Analysis ; Fraps, Principles of Dyeing ; Knecht, Rawson and Rosenthal, Manual of Dyeing ; Hummel, Dyeing of Textile Fabrics ; Cain and Thorpe, Synthetic Dyestuffs ; Rawson, Gardner and Laycock, Dict. of Dyes, Mordants, etc. ; Crookes, Handbook of Dyeing and Calico printing ; Rothwell, Printing of Textile Fabrics ; Leffmann-Weyl, Sanitary Relations of the Coal Tar Colors ; Berry, Coloring Matters for Foodstuffs and Methods for their Detection (being Bulletin No. 25 of the Bureau of Chemistry, United States Department of Agriculture ; this also contains many references to literature on the subject); Bulletin No. 100 of same ; Sadtler, Industrial Organic Chemistry, contains a full bibliography on the subject. The book, Programme of the City and Guilds of London Institute, contains very full lists of books on many branches of technology, including dyeing and bleaching ; Patterson, Colour Matching on Textiles ; Rawson, Gardner and Lay cock, Dictionary of Dyes, Mordants, etc.; Hurst, Silk Dyeing and Printing.