Page:Encyclopædia Britannica, Ninth Edition, v. 3.djvu/833

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cotton.]
BLEACHING
815

"bowls "of the squeezer to extract superfluous moisture. These bowls are thick cylinders of wood, usually in this case made of beech. From the lime squeezer the cloth is carried over winches, and guided through pot-eyes into the

kiers.

FIG. 6. Section of Lime Squeezer.

Bowking.—A bowking kier is an apparatus in which the cloth is boiled. To one old form of kier allusion has already been made. Bowking is now mostly accomplished in closed kiers worked up to a considerable pressure of steam. In the boiling for white bleaching about 80 fi> of lime are required for 2700 lb of cloth, and the boiling is continued for ten hours at a pressure of about 30 Bb. A form of kier very generally employed consists of a strong- vessel made of boiler plate, with a man-hole in the upper part, which can be screwed tightly down. The vessel is about 10 feet in depth, and 5 or 6 feet in diameter, and has a false bottom made of a gird of wood or iron, on which the lowest layer of cloth rests. Up the centre of the kier passes a pipe or tube which reaches higher than the cloth can be piled, and is surmounted by an umbrella-shaped plate. Steam is admitted at the lower part of the kier, and as the pressure accumulates it gradually forces the liquor upwards through the central pipe till, by-and-by, it is dashed with great violence against the umbrella-shaped plate, and thrown over the upper surface of the cloth. It gradually percolates down through the cloth to the bottom, where it is again caught and forced up through the central pipe, and thus a constant circulation is maintained. A very efficient circulating kier, the invention of Mr Taylor of Berchvale, has recently been introduced, of which a sectional representation is given in fig. 7. This kier in outline is like the previous, but it has no central distribut ing pipe. Instead, the liquor is carried by an external pipe to the top of the kier, where it enters and is forcibly thrown against the surface of the cloth. The kier A has a false bottom B as in the previous case, and when filled with cloth and liquor, the liquor percolates by a pipe C into the receiver D, where it finds its own level in the ascending pipe E. Steam is admitted at the lower part of the receiver by the steam-pipe F, and forces the liquor upwards through the pipe E to the top of the kier. The vacuum created in the receiver is supplied from the lower part of the kier, and the flow is facilitated by the pressure of steam from above, and thus a constant steady circulation is maintained. This kier is very useful in cases where a comparatively low pressure is desirable, as in white bleaching, where the coloured headings of the cloth (Turkey red or other coloured threads introduced at the end of a web) have to be preserved.


FIG. 7. Taylor s Circulating Keir.

The bowking apparatus generally used by printers is Barlow s high-pressure kiers, an arrangement in which the kiers are worked in pairs. A pair is shown in fig. 8, one being seen in section ; the dimensions of the vessels are inserted in the figure.


FIG. 8. Bnrlow s High-Pressure Keirs.


The novelty these kiers introduced when first brought out, was that in using steam of 40 K> instead of 5 ft, a greater economy of time and drugs would be effected. Their world- wide application has proved that the inventor s theory has found ample confirmation. The cloth is carried or rather drawn by winches, and dropped into the wrought iron boilers or kiers AA , through the man-holes in the top, two pieces in all cases running side by side. As the pieces are delivered continuously in the kiers, a lad in each spreads a pile of the cloth all round the kier, as equally as possible, so that, when full, the kier shall be packed uniformly to the top. This doth rests on what is termed a false bottom, simply a grid or plate with holes in it, as shown at B. Upon the grid are generally placed a few smooth stones, through the spaces between which the liquor drains from the cloth.

Down the centre of the kier is a pipe C, perforated with holes, for the purpose of distributing the liquor freely into the mass of cloth. The kiers arc connected by a pipe D, leading from the bot tom of one to the top of the other, and vice versa. The steam is introduced through the valves EE . After the kiers are filled with cloth, each holding about 6000 K>, the man-hole lids are screwed down and all made steam tight. A little steam is then turned on to discharge the air from the cloth, which escapes through the pipes FF. This steam, moreover, gradually warms the goods. The alka line liquor or lime water, having been mixed to the proper strength,