Fig. 481.—Section through Glue-pot.
PREPARING GLUE.
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.
WOKKSHOP GLUE-POTS.
In the workshop different kinds of glue-pots are used according to the quantity required. For workshop use the ordinary glue-pot (Fig. 480) may be used. This has an outer and an inner vessel, as shown in the section (Fig. 481). In large workshops, where glue is used in quantity, and steam-pipes are laid on for heating purposes, a tank constructed as shown in Figs. 482 and 483 may be used. It is made of 1/4-in. plate iron or steel, with four holes (c, Fig. 483) in the top, large enough to accommodate buckets or specially made glue-pots; d is a steam-pipe carried nearly to the bottom of the tank, and e is an overflow pipe to carry away the waste water produced by the condensation of the steam. A small hole must be provided at f, or the overflow pipe will syphon all the water out of the tank. A draw-off tap at G facilitates cleaning out, or supplies hot water. When required for use, the tank is filled with water and the steam turned into it, which will cause the water to boil. If steam-pipes are not laid on, the glue-tank may be constructed as shown in Fig. 484, and heated with coal or waste wood.
Fig. 483.—Plan of Steam Glue Heater.
HOUSEHOLD GLUE-POTS.
For home use the glue may be melted in a cup or tin placed in a saucepan of boiling water. A serviceable glue-pot is made as follows: Get a cocoa or mustard tin, and pierce two holes in it opposite each other, about 1 in. from the top; get about 8 in. of tinned wire and run it through the holes, the wire resting on the edges of the saucepan. Another device:—A disused golden syrup tin, about 4 in. by 4 in., is very suitable for the outer pot, as it has a ring round the top, inside, about 3/8 in. wide, on which the flange of the inner pot may rest. In each side of this tin, about 1 in. from the top, pierce a hole, and bend a piece of iron wire into a half circle, place the two ends into the holes in the tin, as shown in Fig. 485, and clinch them over inside. The inner pot may be made from a coffee tin, 3 in. in diameter by 6 in. deep. This, of course, is too deep, so, scribing a line right round the tin 3 in. from the bottom, cut from the top downwards a number of slits 3/4 in. apart to the line. Bend all these pieces of tin, except one on each side, at the line to right angles with the sides of the tin, thus forming a flange about 3 in. wide. Cut down this flange to about 1 in. wide, and the two upstanding pieces to 1 in. high, rounding at the top. In each of these two pieces pierce a hole, and get another piece of. iron wire, bent as before, but slightly shorter; put each end through the holes, clinch over, and the pot is complete, the inner pot appearing something like Fig. 486. Another device:—Fig. 487 shows a 2-lb. syrup tin A, a condensed milk tin B, and pieces of wire C, and explains itself. If the water should boil over it cannot get into the glue, and, when using, the brush is wiped upon the wires C, and that does away with the accumulations of glue commonly seen on glue-pots. A different kind of inner pot is made as follows:—A 2 1/8-in. round hole is made in the lid of a 2-lb. syrup tin, and the ring thus made is put over the top of a 1/4-lb. round mustard tin, and soldered to it at the distance of 1/2 in. from the top of the tin. In running the solder round a small space may be missed to allow the steam to escape, or a hole may be made in a convenient place. The handle may be made by cutting off the screws of two screw-eyes, making holes in the sides of the syrup tin, and soldering them in. The lid of the mustard tin may be used to cover up the glue when not in use. Another device:—Take al piece of suitable wire A (Fig. 488), and make three loops B at equal distances, according to the size of the vessel used. This is placed at a convenient height on the vessel C, so that it well clears the bottom of the vessel D, in which it is placed. A piece of wire E is then placed over the top, the two ends being bent down to come between the wire circle A and the inner vessel C, preferably between two loops as shown. All is then twisted up till it grips the vessel quite tightly. The vessel C is then placed in the outer vessel, and the loops are turned down