Читать книгу The Handyman's Book of Tools, Materials, and Processes Employed in Woodworking - Paul N. Hasluck - Страница 188

Much depends upon the manner in which the glue is prepared. It does not suffice to place it in water, and at once bring to the boil, because this method produces a glue of but little strength. The proper way of preparing glue is first to break the cakes up small by wrapping in canvas and striking with a hammer. If the canvas is not used the glue will fly into small fragments, many of which will be lost. Put the glue into a clean vessel and cover with clean cold water, allowing it to remain until the next day, when it will have absorbed some of the water and present the appearance of lumps of jelly. Pour off the surplus water, and place the glue in the inner vessel of a glue-pot and just cover with water, then keep the water boiling in the outer vessel for two or three hours. To test for thickness, dip the brush in, and if the glue just runs easily without breaking into drops it is fit for use. Some workmen are able to test the thickness by rubbing the liquid glue between the finger and thumb. A drop of suitably prepared glue, if placed on a cold surface, should quickly become a jelly. If too thin it will be some time in hardening sufficiently to be handled, and if it is so thick as to harden almost directly and be unworkable with the brush, more water must be added. The inner pot should never be placed on the fire, or the glue will burn and become worthless, the right temperature for heating being that of boiling water. Do not boil the same glue more than twice—it loses its strength. If only a little is to be used at intervals, allow it after the first boiling to get cold and form a jelly; then pieces of the jelly may be cut off and heated as required. Thus a stock of reliable glue is always at hand.

Fig. 482.—Steam Heater for Glue.