Fig. 591 shows a longitudinal section of Mather & Platt's steam-chest :—A is the body of the structure, of wrought-iron plates, in a cylindrical form ; B is the carriage, and wheeled frame, fitted with square wooden rollers, all geared together by spur wheels, worked by a handle passing through a stuffing box to the outside of the chest ; D repre sents the handles and wheels ; E, pieces hanging on the rol lers; F, perforated pipe for introducing steam ; G, escape pipe and tap for condensed water ; H, movable door, hung with balance - weight ; K, pressure - gauge and safety-valve.
When the goods are ready for steam ing, the carriage is drawn out into the room, and filled with the pieces, which are one after another wound upon an open reel, the selvages being kept paralleL They are then drawn off the reel, and flattened, and a string is drawn through the selvages on one aide, and looped. Through the loops, are thrust wooden rods, resting on the sides of the frame-work. The carriage is run back into the chest, which is closed, and made steam ight, the pressure being regulated by a safety-valve. After the lapse of the requisite time, which ranges from 20 minutes to 1 hour, the chest is opened, and the pieces are taken out, unrolled, and folded loosely, so as to ba ready for rinsing. They are stitched together end to end, and taken first through a cistern of water, next through a very weak solution of bichromate of potash ; then washed, and drained iu the centrifugal, ready for finishing.
Before the colours are printed on, the calicoes are generally " prepared " by the following pro cess :—The pieoes are padded in a solution of stannato of soda, commonly known as " alkaline preparing salts," at 10° Tw., in a machine fitted with wooden rollers. The padding is generally done twice, and, in tho meantime, the pieces are allowed to remain wet for about 1 hour; next they through sours, e. dilute sulphuric acid at 11°-3° Tw., then into pure water, and are washed, so that no free sulphuric acid may remain upon them, but the washing must not be so severe as to remove the oxide of tin, which has been deposited upon the fibre. The pieces are then drained in the centrifugal machine, carefully dried at a gentle steam-heat, and are ready for printing.
For heavy shades, the strength of the solution of stannate may be raised to 24° Tw.; the pieces are left to lie wet for 2 hours, and are then taken through sours at 6° Tw., washed, and drained in
the centrifugal. All these operations are then repeated once more in the same order, and the goods are then dried, Care must of course be taken to keep the sours up to the same point of acidity. Without attention to this point, they become rapidly weakened, and the fixation of the tin being thus rendered irregular, the colour subsequently produced will be uneven.
If preparation with stannate of soda is useful for calico, it ie in general absolutely necessary for worsted stuffs, and mixed goods.
The following are examples of steam colours ;— Amber.—Gum substitute, 15 lb. ; olive oil, neutral, 1 pint ; bark liquor at 12° Tw., 3 gal.; sapan liquor at 8° Tw., 24 pints ; red liquor at 16° Tw., 3 qt. Half boil, and add 6 oz. tin orystals, pre viously dissolved in 2 pints of the red liquor. Mix, and add pint oxy-muriate of tin at 120° Tw Mix well, and strain as fine as possible.
Blacks : (1) Machine work.—Logwood liquor at 6° Tw., 1 gal. ; staroh, 11 lb. ; boil, and add, whilst still hot, copperas, 5 oz. ; stir thoroughly, and, when the mixture has grown almost cold, add gallipoli oil, 2 oz. ; and nitrate of iron, well neutralized, 10 oz.
(2) Another black.—Logwood liquor, 12° Tw., 1 gal. ; gall liquor, 9° Tw., 1 qt. ; mordant, 1 qt. ; flour, 2 lb. ; starch, 6 oz.
For the mordant, mix acetio acid, 1 qt. ; acetate of copper, 11 qt.; black liquor, 24° Tw., 11 qt. ; red liquor, 20° Tw., 1 qt.
(3) Black for Calioo.—Dissolvo in water 5 lb. 7/ oz. solid extract of logwood, and allow the liquor to settle. Dissolve separately in water 171 oz. gum tragaoanth. Mix the two solutions, and boil. Boil out 2 lb. 3 oz. gall-nuts in water, and add the decoction to the above, making up to 171 pints. Let cool, and stir in 2 lb. 3 oz. nitrate of iron at 304° Tw., and the same weight of black liquor at 26° Tw. Print, and bang up for 2 days, or preferably for a few hours ; steam well, and wash.
(4) Black for printing Cotton Yarns.—Dissolve in water 5 lb. 7 oz. solid French extract of log wood, and 171 oz. gum tragacanth. Make up the mixed solution to 21 pints, in which dissolve 41 oz. extract of bark. Let cool, and Air into the mixture 2 lb. 3 oz. black liquor at 301° Tw., and 17 oz. nitrate of iron at 98° Tw. Print, hang up for 2 days, steam, and wash. If a very blue tone is required, the nitrate of iron is left out.