Do not wipe off the glue which squeezes out from a glued joint (unless for some special reason) nor wash it off with water. Let it harden, and clean it off after the joint has set. It helps protect the joint.
Do not be in haste to unclamp your work. When to release it depends on the kind of wood, the kind of work, and the circumstances under which the gluing is done, and no exact time can be set. If for some temporary and unimportant purpose and in soft pine, for instance, you can unclamp in a few hours or even less, but for important work, which is to hold permanently, twelve hours is scarcely time enough even for soft wood and hot glue, and twenty-four hours is none too long, for though the glue dries quickly to the touch, it takes considerable time to get thoroughly hard. It is safer to allow more time for hard wood. The thickness of the stock makes a difference also. Large junks and blocks and boards glued flatways require more time than ¼" stock, thin strips, or little splinters. You can tell something by the condition of the glue that is squeezed from the joint. Liquid glue sets much more slowly, and twenty-four hours is soon enough to release the work under average conditions. The warmth and dryness of the air make a good deal of difference. Under unfavourable conditions more than forty-eight hours may be required.
If for any reason you cannot clamp a joint, after applying the glue rub one piece back and forth upon the other a few times.
Rub wax, soap, or tallow on any part which must not be stuck by surplus glue which may exude from a joint, as in the case of a panel which may become stuck by the glue used in fastening the frame (see Doors and Panels).
To glue two pieces where the surface is to be planed or trimmed at the joint, do not glue them together after they are planed or trimmed, but glue them first, and plane or trim them afterwards, taking care to have the grain of the pieces run in the same direction (see Jointing).
To glue pieces end to end, or as in a mitre,—that is, "end wood,"—first size with thin glue to stop the pores, else the glue will be quickly soaked up. Then, after allowing this coat to stand, glue in the ordinary way. But glued joints in end wood are seldom good and are to be avoided.
A great deal of glued work comes apart, and a great many mistakes in putting work together are caused by not understanding, or not bearing in mind, the way wood expands and contracts and warps and winds from heat and cold, dryness and moisture. This is an important matter if you wish to do good gluing. Do not think that all that is necessary is to have your wood dry and that then you can glue the pieces together in any relative positions. Veneers or thin pieces are sometimes successfully glued with the grain of the pieces running at right angles, as seen in chair seats, but as a rule avoid gluing wide pieces together with the grain running at right angles. See Laying out the Work, in Chapter IV.; also Jointing.
Glue-Pot.—This can be bought of copper, iron, or tin. A medium-sized one is more useful than a very small one. Have a cover to keep out dust and loose particles.
If obliged to make shift without a proper glue-pot, always use two dishes like a regular glue-pot, with water in the outer one, on the principle of the double boiler used for cooking, else the glue will be sure to burn and be spoiled. Two cans, such as are used for tomatoes or other vegetables, can be used on a pinch, one being larger than the other and fastened in place with wire or in some way to keep the smaller can from moving around too much; but a regular glue-pot is much better. See Gluing.
