Styles of Printing

Resists Under Aluminium and Iron Mordants.

For the production of this .important class of goods, use is made of the fact that alkaline citrates prevent the fixation of the mordants. The cloth is first printed with citrate of soda (or sometimes citric and tartaric acids for iron mordants)•, then dried, and again printed over the previous impression, with either a fine "all over" pattern or flat uniform ground, in iron or aluminium mordants. The fabric is then aged, dunged, washed and dyed as already described, with the result that, wherever the "reserve" of citrate or acid was printed, a white pattern is left on a figured or plain ground. The fine patterns printed over "resists" are called "covers" and the plain grounds "pads," hence the name cover and pad style in cases where, as frequently happens, a dark cover and a light pad are both printed over a white resist. The cover and pad style is, for the most part, restricted to dyed alizarine purples, under which red, black, dark purple and white can all be resisted at the same time, thus giving rise to very pleasing effects.

In the case of resists under steam, alizarine red, and pink, a reserve composed of citrate of chromium alone, or in conjunction with citrate of soda, gives the best results. The goods are first prepared in alizarine oil and then printed with the following: 10 lb. china clay, 1 gal. citrate of soda, 54° Tw., 1 gal. citrate of chromium, 42° Tw., 1 gal. water, and 21 gal. British gum paste. After printing the above, the goods are dried, again printed either with cover or pad or both in alizarine pink, dried, steamed for i1 hr., well washed and soaped. On leaving the steamer the parts printed with the resist are yellow, but become quite white on soaping. Like the purples, the alizarine pinks can be reserved in colours. For blue, green, yellow and violet the ordinary steam basic colours are used with additions of citric or tartaric acid; e.g., 7 lb. china clay, 1 gal. water, 61 gal. British gum paste, 2 lb. methylene blue, 1 lb. citric acid and 1 gal. acetic acid. Boil, cool and add a gal. 5o% tannic acid solution in acetic acid. The resisting' of aniline black is effected by the use of alkalis, which, as Prudlomme discovered, prevent the formation of the colour. White and coloured resists may be applied either before the liquor is padded with the prussiate black liquor or after padding, in which case it is often termed a discharge black. The black is developed except where the resist (discharge) has been printed. For the true resist process it is essential that the printing mixture shall contain some insoluble plastic material, such as zinc oxide.

Variations.

Variations in the appearance and properties of portions of textile fabrics are frequently brought about by print ing. A crimped surface on cotton fabric may be obtained either by printing caustic soda (6o-7o° Tw.) thickened with

British gum, then washing ; or by printing a very strong thicken ing on to the cloth and then passing the whole piece through a solution of 60° Tw. caustic soda and washing. In the first case the printed parts shrink, and so make the rest appear crimped; and in the second case, the printed parts, being protected from the action of the alkali, are caused to appear crimped by the shrinking of other parts of the material. These effects are usually applied in the form of stipes which is the best pattern for show ing the effect to advantage. It is an adaptation of mercerizing.

Matt, lustring and delustring effects on fabrics composed wholely or partly of artificial silk of various kinds is carried out to a large extent. F. Scholefield produces an effect which closely resembles wool and silk by printing sodium sulphite, or other desulphurizing agent, on to a fabric composed of viscose silk containing sulphur (unbleached viscose). The latter, when spun in a suitable form, looks somewhat like wool and feels warm, but wherever it is desulphured the lustre of silk appears. Alter natively, if the sulphur yarn, of which the piece is composed, is fine and smooth it shows an opalescent lustre, while the delustred portions have a bright silk-like lustre. The lustre of acetate silk is altered by steaming alone. If protective agents in the form of organic acids are printed on to a piece of such artificial silk and it is then steamed, the lustre of the unprotected portions is re duced or lost while that of acid printed portions remains unim paired. In nearly all cases of which these effects are typical, it is possible to combine the lustring and delustring style with one or more of the other styles of printing. In a very simple way effects of a novel character are obtained; for example, a piece of sateen, composed of cotton warp and acetate silk weft, is printed in fine check pattern with caustic soda, below mercers izing strength but still sufficiently strong to impart some modifica tion in the dyeing property of the fibres. It is then dyed in one bath with a mixture containing a cotton blue and golden yellow for acetate silk. On one side the cloth appears almost as if it were composed of threads of metallic gold woven so as to show a transparent and shot dark and light blue background ; on the reverse side the cloth appears mainly dark and light blue check, shot or intercepted with some gold threads. Warp printing is utilized to a considerable extent for the production of cretonnes, and other heavy weight fabric, for by this means it is easy to get good colour penetration like that obtained in dyeing. Holden (Nov. 1928) has obtained increased dyeing with direct colours and indigosols by printing cloth (velvet) with gelatine and then steaming.