We use a connector in the form of glue to connect non-dismantled wooden elements, which, after drying, forms a durable bond that connects wood with wood. Animal adhesives are divided into glutin adhesives for "hot" joining and casein adhesives for "cold" joining.”.
Animal adhesives are soluble in water, synthetic adhesives, however, not always; then they are dissolved with chemicals.
The elements of the objects to be glued should be carefully cleaned of dust, sawdust, dirt and grease, because the glue in polluted places does not penetrate deep into the fibers and will stick to them only superficially, giving a non-permanent joint. Cleaning the surfaces alone will not ensure their permanent connection. These surfaces should be tightly matched to each other, that is, adjoin each other with the entire plane, and not just a part of it.
Tight adhesion of the surfaces to be joined is very important for good bonding, because in places of their poor contact, a thicker joint will be formed from the adhesive, which has a lower strength than a thin weld.
Bone glue. It is made of animal bones. It is not resistant to moisture, therefore we only use it to glue such items, which will be used in dry rooms. For good gluing results, you need to prepare the glue properly, that is, make a solution out of it. Bone glue is sold mostly in the form of tiny pearls, less often in the form of plates. The latter must be broken into small pieces with a hammer before use, put into a clean vessel and pour cold water twice the amount of dry glue (we do the same with pearls).
After a few hours or a day in the case of glue in tablets, when the glue swells, we drain off excess water, put the vessel in a cauldron also filled with water and heat it over low heat until the glue dissolves completely. The temperature of the solution should not exceed 70-80 °, because its viscosity and adhesion decrease at higher temperatures. To apply the glue solution, use wooden spatulas made of alder or poplar wood or bristles..
Casein glue. For one-time use, we take as needed 25-30 g of glue and mix it in a clean clay vessel, glass or enameled in 100 ml cold, boiled water. Mix the solution, then set aside for 30 minutes, that it dissolves well in the water.
Only after this time can it be used for gluing. The thoroughly mixed glue solution should be cream-thick and contain no lumps of undissolved casein. The glue, mixed in the given manner, can be used continuously 5-6 hours, as it then gradually hardens and becomes unusable. There is no point in diluting casein glue with water. Casein glue is used cold, so there is no need to rush to apply it to the surfaces to be glued.
Synthetic adhesives are made of synthetic resins (produced by chemical reaction methods) in the form of solutions in alcohol or water. The most popular and the most convenient to use synthetic glue is vicol. It is commercially available in ready form, resembling creamy, thick cream. In case of thickening, it can be slightly diluted with cold water. The glue is applied with a brush to the glued places, and the workpieces are held tightly together, because wikol should have the thinnest possible layer – then the connection is permanent. The basic components of other synthetic adhesives are urea-formaldehyde and phenol-formaldehyde resins and epoxy resins., from which many types of synthetic adhesives are now produced. These adhesives do not undergo any changes under the influence of temperature, couples, moisture and time, moreover, they provide a joint that is stronger than wood. They can be used to glue not only wood with wood, but also wood with various metals (table, copper, zinc, brass, tin, etc.). Detailed descriptions of use can be found on the packaging of adhesives on sale.
Methods of gluing wood. The glue is applied to the surface of the joined elements in different ways and depends on the type of joint, quality of wood, the size of the glued elements, the type and quality of the adhesive and the experience of the person performing the bonding.
When gluing boards from boards, the glue is applied simultaneously to both previously heated surfaces with a bristle brush or a wooden spatula. (small planes). After applying the thinnest possible layer of glue, it is necessary to wait a while, so that the glue can partially soak into the wood, and only then fold the two planes together. If we use hot glue to glue the boards, the soak time will be shorter (several seconds), if it will be casein glue or vicol – soak time will be longer (2-3 minutes). To allow the glue to soak into the wood fibers faster, you need to use glue with appropriate density adapted to the hardness of the glued wood. Too dense glue will not soak into the wood and will not form a bonding layer with it (welds).
Drying of the squeezed elements should take place at a similar or similar temperature as well as gluing. The drying time may vary depending on the size of the joints, type of wood, the type and density of the adhesive, the ambient temperature as well as the air humidity and the pressing force. Too humid air at the point of gluing extends the drying time of the glue, zbyt search – speeds them up.
The drying time of the pressurized joint for bone glue is from 1 do 5 hours, for casein glue from 6 do 8 hours, for synthetic adhesives from 0,5 do 2 hours.