Fig. 484.—Heating Arrangement for Glue Tank.
Figs. 485 and 486.—Household Glue-pot.
Fig. 487.—Household Glue-pot.
GLUE BRUSHES.
A glue brush can be bought for a few pence. If the hairs are too long the brush must be tied to make them shorter as far as their action is concerned. Start by placing the twine as in Fig. 489, and then bind it tightly round the hair until the brush is sufficiently short; finish off by passing the end of the twine through the last two coils (see Fig. 490) and drawing tight, and then turn back the loose ends and secure each of them with a tack (see Fig. 491), to prevent the ends slipping down. The brush should not be put into glue until ready for use, and, when finished with, should be washed in hot water. The following is a method of keeping glue brushes in good condition. Fix a stout wire across the pot in one of the ways already described. By pressing the brush against the wire to free it from superfluous glue, the sides of the pot will always be clean, the glue will heat quicker, and no material will be wasted. It is a good plan to cut away one side of a small-sized screw-eye to transform it into a hook, and put it into the handle just below the ferrule, or about 2 in. from the bristles; the hook holds the brush on the wire clear off the bottom of the pot. A brush left to rest upon the bottom of the pot quickly becomes too crooked to use. Fig. 492 illustrates a brush that has been spoilt in this way. The bristles refuse to stand in the proper position, and it is useless for particular work. The following is a method of improving the brush, though a tool in such condition can never be made to work thoroughly well. First remove the glue by washing, then hold the bristles in very hot water for a few minutes and refill the brush again with glue; get a strip of old rag, and, holding the brush as shown in Fig. 493, wind the material round the entire length of the hair, and secure the end by tying twine round tightly. The bristles will now stand erect, and the brush is put aside and the binding allowed to dry hard on it; in the course of a day or two the brush may be held in hot water and the binding peeled off. Once doing is not enough if the tool is in a very bad state, but after the same process has been repeated several times it is usually in good workable condition. Glue brushes are so cheap, however, that it is doubtful whether the result is worth the trouble. An effective glue brush can be made out of a piece of common cane, and the cane brush is preferred by many competent and practical workers to any other. Take a piece of rattan cane about 8 in. long, cut away the flinty skin for an inch or so at one end, soak this end in boiling water for a minute or two, and then hammer this till the fibres are softened and loosened, the only care required being not to cut them off while hammering (see Fig. 494). Such a brush will last a long time—in fact, as long as there is any cane left from which to hammer out a fresh end.
Fig. 488.—Household Glue-pot.
METHOD OF GLUING.
Glue should be used as hot as possible and in a warm room. The pieces of wood to be joined should be warmed before being put together, and should be well fitted so as to get as little glue in the joint as possible; the glue should be well rubbed in with a brush or by rubbing the two pieces of wood together, and the joint should be made close by clamping, tying, or rubbing, so as to squeeze out all superfluous glue (see pp. 183 to 185). When practicable, as it generally is, except in the case of large veneers, the glued pieces should be worked against each other with gradually increasing pressure, to expel any air between them, and to squeeze out as much of the glue as possible. On the extent to which this is managed much of the strength of the joint depends. The thinner the film of glue between the pieces, the more firmly will they adhere; nothing is gained by leaving a thick layer of glue. The quantity of glue in a joint should be so small that, if the two surfaces are true and bear uniformly on each other, its presence should be denoted only by the hair line which marks the joint. The joint should be made as quickly as possible, and after the pieces are fixed they should remain in a warm place for at least twelve hours. If a joint is broken after it has commenced to set, no amount of clamping will make a good job of it; the glue must all be cleaned off and the joint made again. When the wood is porous it will be of advantage to size the surface with some very weak glue. This will fill up the grain and prevent the glue from sinking into the wood when the joint is made, but let this size be quite dry before gluing, or the effect will be to cool and dilute the glue. The methods of gluing on veneers are described fully later. Great care should be taken that dust, grease, or oil does not get on the surfaces to be joined, or the glue will not hold. Some woods are, however, of a greasy nature. Take teak for instance; if the wood is not thoroughly dry the glue will not set on it, but will peel off. Wood of a greasy nature should not be used where glued joints are employed, or for veneering. A later chapter will deal comprehensively with gluing up joints, etc. (see pp. 183 to 185, and p. 187).
Figs. 489 to 491.—Shortening Hair of Glue Brush by Tying.
Fig. 492.—Glue Brush with Bent Hair.
LIQUID GLUES.
Liquid glues, such as Le Page’s and “Scoli,” have become popular. The advantages of these liquid glues are that they are always ready for use, requiring no heat, and that they do not spoil by being exposed to the air, though they then become thick, simply from the evaporation of moisture. The remedy, of course, if this happens, is to add a little more water, but in practice, with ordinary care, this is seldom requisite, and is not desirable. In very cold weather a little warmth is necessary, but if kept in a warm room or placed near a fire for a time, liquid glue is soon fit for use. As already stated, it is not applied hot. For work requiring a colourless or almost colourless glue it is unsurpassed, and as it does not set so quickly as the ordinary kind, it is well adapted for marquetry and inlaid work generally. When it does set it possesses great tenacity if properly used, that is, thinly applied and well rubbed in. Although it is not better than best quality animal glue employed under the most favourable conditions, it is certainly superior to ordinary common glue which has not been made, mixed, and used with skill and care. At first sight it may seem expensive, but as a little of it goes a long way, and as it does not waste by keeping, it will be found, when required for occasional use only, to cost in the end but little, if any, more than the usual kind.
Fig.