STYLES OF PRINTING The designation of any particular style of printing is based on its method of production. There is a large number of these recognized technically and it frequently happens that a multi coloured effect involves more than one style of work, but in such a case it is usual to apply the name of the predominating style to the whole. Styles may be grouped under the following headings : Direct printing (many colours for which special methods have been devised and are frequently classed under special groups, for example para red or insoluble azo style can be applied directly in printing) ; dyed style; discharge style; resist printing; proc esses of producing differences of texture or lustre in the textile fabrics either with or without colouring.
Direct Printing.--This style is largely used and can be applied with almost all types of colouring matters, if suitable ingredients are chosen which will react, in steaming, to produce colour lakes fixed on the fibre. In this way very fast effects can be produced, for this style of printing differs entirely from dyeing with direct cotton colours which are seldom used in cotton printing. The mor dant colours, applied with a salt of alumina (frequently the acetate or the sulphocyanide), iron, or chromium, together with thicken ing and acetic acid, give bright and full shades of good fastness.
For alizarine red of full brilliance it is necessary to add a little oxalate of tin and lime, together with a little acetic, tartaric or oxalic acid, to obtain the brightest shades. In most cases, too, it is preferable to treat the cloth before printing with an oil "prepare" which consists of 5o parts ricinoleic acid, 20 parts ammonia, 20 parts sodium carbonate made up together to i,000 parts. After printing, the goods are steamed and the colour is fixed. When utilized for the fixation of mordant colours this is sometimes known as the "extract style" because it was originally used in the case of madder, logwood and quercitron bark extracts. For printing alizarine red the following printing paste (made up in parts by weight) may be applied to cloth treated with oil prepare:— 47 parts water, 13 starch, 13 alizarine (2o% paste), 3 acetic acid 9° Tw. Boil, turn off the steam and add 2.5 chlor oil (made by mixing equal parts of olive oil and 7° Tw. bleaching powder solution to form an emulsion), 2.5 stannic hydrate 20% paste, 2.5 oxalate of tin. Cool, and immediately before use add cold 3.5 acetate of lime 23° Tw., 4 nitrate of alumina, 23° Tw.
and io sulphocyanide of alumina 20° Tw. If it is desirable to print cloth which has not been previously oiled (e.g., when aniline
black is to be printed side by side with alizarine) a special emul sion may be made with sulphoricinoleic acid, gum tragacanth and acetic acid. There is then no danger of the black being spoiled by the alkali in the oil prepare.
chlorate of potash.
Indigoid Colours.—There are three methods of printing indigo blue : The glucose or Schlieper and Baum process; the hydro sulphite process ; and by the utilization of already reduced com pounds such as indigosol and soledon colours.
In the first method the cloth is first prepared with glucose (30o parts grape sugar to 700 water) dried and then printed with i so indigo (20%) and 85o alkaline thickening (made by mixing 3o maize starch, ioo dark British gum and 87o caustic soda 77° Tw.). The goods are steamed as quickly as possible after printing by running for z min. through an ager at ioo° C (moist steam). They should then appear a brownish olive colour in the printed parts, and are exposed to the air, washed in running water, treated with I° Tw. sulphuric acid, and again washed. Light shades of indigo can be oxidized by exposing to the air. This is perhaps the cheapest way of printing indigo and the colour is in no way inferior to that produced by the second method. The hydrosulphite process overcomes the necessity of preparing the cloth, for in this process indigo is printed in admixture with hydrosulphite formaldehyde. This compound dissociates in steam ing, the hydrosulphite reduces the indigo and the cloth is locally dyed. The goods are then "aged" and allowed to lie a short time after which they are washed in cold water first, until the indigo is thoroughly re-oxidized, and then in hot water or soap. The com position of this printing colour is as follows :-200 parts hydrosul phite N.F. (or ioo of the concentrated product), 45o parts alka line dextrine paste, i so parts indigo 20% paste (ground up in gum), 200 parts alkaline dextrine paste. Thickening-15o parts dextrine or British gum and 85o parts caustic soda, 70° Tw.