There are several methods of singeing In vogue, viz. by hot plate, by revolving hot cylinder, by cake flame and by gas flame. Fig. 337 represents the arrangement with two hot plates. The pieces are depressed au to and caused to pass rapidly over two red-hot plates P P. D represents an iron frame, narrying four bars for depressing the pieces, which can he raised or lowered by the chain C. G G is the passing piece. The two plates are heated by the same furnace, that which the cloth tounhes last getting the direct flame of the furnace, the other covering the return flue leading to the chimney. By this arrangement, the piece is only partly singed by the first plate, and sci dried that the second plate completes the singeing to the best advantage. After passing the plates, tho pieces are drawn between twn rows of steam jets at K K, through a water trough B, and between the rollers R R, to extinguish any sparks which may adhere to the cloth. H' is a hopper for leading away the products of combustion, and H is a small engine far driving the rollers R R. Formerly, thick cast-iron plates were used ; they have been, however, almost universally replaced by cast-copper semi-cylindrical plates about 1 in. thick. These not only last much longer, being less liable to crack or get out of shape, but they are more easily kept free from the scales produced by oxidation, and present a smoother surfane. With careful firing, such a plate may last several months without having to be mended, An essential point to be attended to is not to allow the edges of the plate to come into direct contact with the furnace flame; to avoid this, they should be made to rest well on the brickwork, or in a bed of clay. If clay is not used, a little sand along the exterior edge suffices to confine the flame beneath the plate.
A difficulty in plate singeing is to keep the plates at one regular strong red heat, the cooling action of the rapidly passing calico being very conaiderable. Hence, in some instances, the two plates are heated by separate furnaces. The difficulty is completely overcome by Worralrs revolving singeing roller, as fitted up in the bleaching department of Messrs. Edmund Potter and Co., and represented in Fig. 338. The ordinary semi-circular copper plate is here replaced by a cast-copper tube A, through which the flame from a furnace passes. heating its entire surface from end to end up to a good strong red heat. The tube rests with its bare weight on a pair of rotating pulleys B B at each end, from which it receives its own revolving motion by friction. The ends of the tube bear close up to the brickwork of the furnace and flues, and the draught is suffi ciently strong to prevent the flame from appearing through the remaining chink. D is a steam box for extinguishing the sparks, E E a pair of traction rollers, F the folders. At G, the piece travels for some distance to cool, passes round a roller, and returns. H is the hopper leading to the chimney. If necessary, the pieces can be singed twice on one side with the same tube, by being made to pass above and below, and they can be made either to merely graze the tube or to wrap pretty consider ably around it, by suitably arranged depressing bars C C. It is at once evident that the passing cloth comes continually in contact with a fresh surface of the revolving red-hot tube, and a regular even singe is the result. It may be remarked in passing that it is most economical to employ a
system of mechanical stoking, such as Jukes'.
A defect in the methods described is that, by being pressed against the plate or tube, the cotton hairs of the cloth are flattened down, which rather hinders them from being readily singed, and often necessitates a repetition of the operation. This defect is partly removed in the coke flame singeing arrangement, and wholly removed in that of the gas flame. Experience has shown that the coke flame alone is not sufficiently powerful ; hence it is used, as at Messrs. Schwabe's bleach-works, in conjunction with the copper plate. Fig. 339 shows such an arrangement. It consists of a coke furnace D covered with a cast-iron plate having a long narrow slit in it, about 3 to 4 in. wide. By means of a fan, air is blown into the side of the ash-pit, all other openings to admit air being closed. When started, a sheet of clear, smokeless flanae 1 to 3 ft. high rises through the slit, scross which the grey cloth is rapidly passed, on to the hot plates P P, through the steam box X, over the damping roller at T, to be folded down at H. The flame is depressed and spread out at C, so that it covers 1 to 2 ft. in length of the passing fabric ; and since the downy hairs are not flattened down, the dried and partially singed surface is thoroughly singed on the plates. In this, as well as in the arrangements mentioned previously, Et hopper over both plate and flame leads off the products of combustion into the chimney by the flues F F. R R are rollers for guiding the cloth ; G is u traction roller driven by all engine ; S S are perforated steam pipes in the steam box.
By far the most cleanly method of singeing is that with the gas flame. When first introduced, the flame was drawn through the passing cloth, and the general complaint was that the latter became too much impoverished, the nap in the centre of the fabric being burnt away. This defect is now completely removed, and the machine introduced by Tulpin, and further improved by Messrs. Mather and Platt, is a very effective arrangement. Fig. 340 represents this admirable machine. It consists essentislly of two rows of ordinary gas burners B B extending across the width of the cloth to be singed. By means of two small metallic rollers D D, the cloth is brought into contact with each side of the flame, which is drawn up between the rollers by means of an exhaust fan F. Tho cloth is thus singed twice by the same flame, and, being presented to it while passing round the small rollers, the nap is made to stand up in the best possible condition for being singed off. The machine can be so threaded that the cloth may be singed twice on each side or four times on one side. The gas is mixed with air just previous to being burnt, arid is so perfectly consumed that there is no deposition of carbon ; the products of combustion also are carried off in a perfect mariner by the canals E E. A A are g-uiding rollers, G G traction rollers ; C is a lever, by means of which the gas flames can be lowered away from the cloth, in case of a stoppage ; J J is the fold ing arrangement.