Читать книгу The Handyman's Book of Tools, Materials, and Processes Employed in Woodworking - Paul N. Hasluck - Страница 185

In making glue from shredded skins (chiefly those of rabbits), the processes at a large factory in America are as follow: 350 lb. of shredded skin and about 400 pailfuls of water are put into a suitable vat and boiled for two hours, the material being well stirred every fifteen or twenty minutes to prevent it settling. The liquid is then run off from the bottom of the vat and strained in a press, which may be about 4 ft. square, 3 ft. high, and made of wooden slats. The interior of the press is lined with bagging, and through this material the liquid is strained or pressed by means of a hydraulic jack. The hot strained liquid drops into a vat below, whence it is conducted by means of hose into barrels. In from eight to ten hours the stuff is cool, and has a skin formed on the top; in warm weather ice is laid on this skin to harden it; this is size. For making glue, the strained liquid is run into coolers, these being wooden troughs lined with zinc, and in twelve hours’ time the material, then in the form of a jelly, is loosened from the trough by running a wire along it, the wire being bent to conform with the rectangular section of the trough. The block of jelly is cut up into cakes, and these are then sliced in an arrangement of fine wires stretched tightly across an iron frame about 1/2 in. apart; this frame is drawn through the jelly. The drying frames, upon which the slices of jelly are then placed, are about 5 ft. 6 in. long and 2 ft. wide, and are made of galvanised wire netting. The frames, when full, are placed in racks through which the air can circulate freely. It takes but a few days for the jelly to dry in a cool west wind; yet a system of artificial drying, by means of which the size becomes glue in but a few hours, is now being practised. In drying, the material shrinks to one-half its former bulk. The hard glue is now washed to remove dust, etc., and to produce a glazed appearance. In some factories the cakes of glue are cut up into small pieces by means of two rotary knives, each making 300 revolutions per minute. First the glue is passed between two 4-in. toothed rollers which hold it in position and draw it forward after each stroke of the knife.