In calico printing it is necessary to bring the mordant or the color into that state of consistence that it will not spread in the cloth beyond the limit of the design. The usual mordants are alum or sulphate of alumina, acetate of alumina., peroxide of iron, prctoxide of tin, and oxide of chronic : their solu tions are made of the proper density by thickeners, such as wheat, starch, and flour ; other thickeners are used, as gum arable, British gum, gum senegal, traga eanth, jalap, pipe clay, dextrine, potato and rice starch, sulphate of lead, with gum, sugar, molasses, and glue. These with either the color!, or mordants are prepared in vessels furnished with steam jackets.
The manner of applying a pattern on cloth is called a style : of these there are six.
1. The madder style.
2. Printing by steam.
8. The padding style.
4. The resist style.
5. The discharge style.
6. The china blue style.
The madder style is not confined to that color, but the process is applied to many others. In it the cotton is first printed with a mordant over those parts where it is desired. to have a color pro duced. When the mordant has been laid on by the cylinder the cloth is hung up in a room for a few days, when the mordant has suffered an alteration where by it becomes insoluble, and fastened into the fibre of the cloth. Any portion of the mordant which remains soluble has now to be removed, or the color when applied. would pass beyond the pattern. It is removed by passing the dry calico through a warm mixture of cowdung and water. This operation is called dunging. It is then washed in water in a urine pit, and again in a dash wheel. By this process the thick paste is removed which accompanied the mor dant. The difficulty of procuring cow dung in sufficient quantity has led to the employment of other substances, which are easily procured, and which are found on analysis to bo the active agents in the dung : thus solutions of phosphate of soda and phosphate of lime, thickened with glue, are used under the name of substitute for this purpose. After wash ing in cold water, the cloth mordanted is rinsed through a weak solution of substitute and size, when it is ready for the color : this is laid on by drawing the cloth for two or three hours through a colored solution (see DYEING); the color attaches itself 'permanently to those por tions of the cloth to which the mordant has been applied, and form a chemical compound with it. On theportions not mordanted the color is so feebly attached as to be removed by washing in soap and water, or in bran and water, or in a dilute solution of chloride of lime. This is called clearing. ° The processes for finishing a piece of cloth, even with one color, are very nu merous : thus if a rod stripe be required on a white ground, no less than nineteen processes have to be passed through, viz.
1. Printing on mordant of red liquor (acetate of alumina) thickened with flour, and dyeing. 2. Exposure of cloth till mordant is altered. 8. Dunging,. 4. Wincing in cold water. 5. Washing at the dash-wheel. 6. Wincing in dung sub stitute and size. 7. Wincing in cold water. 8. Dyeing in madder. 9. Wincing in cold water. 10. Washing with dash wheel. 11. in soap water with a salt of tin. 12. Dash-wheel washing. 13. Win cing in soap water. 14. Wincing in a so lution of bleaching powder. 15. Washing at the dash-wheel. 16. Drying by the water extractor. 17. Folding. 18. Starch ing. 19. Drying by steam.
From this it may be seen how impor tant the washing and rinsings are. In steam printing the mordant is first laid on and the cloth then dipped in the color vat : union does not however take place between the mordant and the color until steam is brought into contact with the cloth, when immediately the two unite. In some instances the cloth is hung in a room into which steam is ad mitted. In other, the goods are put in a box made almost steam tight and the steam admitted through apipe perforated with a multitude of small holes ; most commonly the cloth is wrapped round a cylinder perforated with holes into which the steam is admitted by a pipe. The temperature is kept at 212° to pre vent condensation, which would make the colors run ; a higher temperature is injurious. The steaming is carried on for half an hour or less according to the nature of the color. This gives a great
brilliancy and delicacy of finish to the cloth. A variety of cheap goods are printedin fugitive colors ; these, not being fixed by steaming or by a mordant, are called spirit or fancy colors : they wash off.
The padding style is only applied to mineral colors. The cloth is uniformly imbued with a color and then dried. This color is sometimes obtained by once dip ping in the trough; at others it is neces sary to dip the cloth first in one mineral solution and then in a second, when an insoluble color becomes fixed in the tissue ; after each dipping the cloth is dried, or the cloth may be padded in one solution and afterwards winced in the other. To produce a design on a white or colored ground, the cloth is printed with one of the solutions and then padded or winced in the other. In the resist style the cloth is first printed with a resist paste to prevent the cloth from taking up' the color when it passes through the dye bath. Some resists act mechanically, such as fat resists, these are used for silk ; others act chemically, such as acetates of copper and lead, chlorides of zinc, and mer-, cury, and arsenate of pota311, thickened with gum, pipe clay, and oil. The dis charge style, is that when a white or col-, ored pattern is to be produced upon a colored ground. Here the mordanted cloth is printed with a substance called the discharger, which acts either on the coloring matter, or on the mordant, by converting them into colorless or soluble matters, which may be removed to allow the parts thus discharged to be died of another color. Vegetable and animal coloring matters are discharged by chlo rine and chromic acid, and a mordant is usually discharged by an acid solution, such as lemon or lime juice, cream tartar, oxalic, citric, and weak sulphuric acids, thickened with gum or starch. In this way are produced the imitations of Ban dana handkerchiefs, in which white fig ures are formed on a ground of Turkey red by means of a solution of chlorine, which is made to flow through the red cloth on certain points defined by the pressure of hollow lead types, inserted in plates of lead contained in a hydraulic press. This is furnished with pattern plates, one fixed on the upper block and the other on the lower, or movable plate.' Fourteen pieces, previously dyed with Turkey red, are laid flat and smooth one on another, the whole is wound on a roller at the/back of the press. The first yard is then unwound and laid flat on the slab of the machine. Then the workman turning a handle brings the pressure to act from a hydraulic machine, and the bed plate rises slowly till the cloth comes in contact with the upper horizontal plate ; such is the power of the machine that the cloth is pressed between the two plates with a force of 300 tons. The chlo rine liquor is then poured into the trough on the upper plate, and after remaining a short time is drawn off by a small cods:, the pressure is removed, and the bed plate sinks down; the cloth is now with drawn and comes oat diversified with white spots, which are as clearly defined on the lowest of the 'fourteen as on the top one. The red dye has here been im mediately removed from the stuff by the chlorine; fifteen minutes is found to be a sufficiently long exposure. These white spaces are occasionally dyed of another color subsequently.
The China blue style is only practised with indigo. The bleached cotton is printed of the desired pattern with a mix ture of indigo, orpiment, sulphate of iron, gum and water. It is then exposed to the air for two days and then stretched on a frame. This is immersed in three cis terns containing different liquids ; 1st, in Milk of lime ; ad, in a solution of sul phate of iron ; 3d, in a solution of caus tic soda. The frames are dipped several times alternately in 1 and 2. The dip ping in No. 3 is less often, but follows immediately that into 2. The insoluble indigo which had been applied to the surface becomes into solu ble indigo or indigotin, which is dissolved and transferred to the interior of the fibre when it is gradually precipitated in the insoluble form.