Animal glue is obtained by digesting bones, skin, tendons and other organs of animals. The obtained substance gains the bonding ability due to two substances - glutin and chondrin. The first is in the bones, connective tissues and skin of animals. High glutin glue has the best bonding properties. Chondrin is the main substance in the structure of cartilage. Adhesive containing a high concentration of chondrin does not have sufficient bonding strength.
Specifications
The purity and quality of animal glue depends on how thoroughly it was cleaned at the factory, as well as on the method of extraction of materials for the preparation of the adhesive.
In the event that mineral acids, caustic soda, lime, potassium chloride were used for the manufacture of glue, the substance obtained after cooking is unsuitable for use.
Quality control of animal glue
A quality glue solution after digestion should not change the color of the litmus paper. When immersed in cold water, the glue should swell, a hot solution dissolves in hot water.
The glue produced using the correct technology should turn into jelly during cooling. Poor substance with poor bonding ability does not freeze. Also chilled glue is not able to freeze if acid (acetic, hydrochloric, nitric) was added to it.
If the glue has been kept on fire for too long, violating production technology, it will also not freeze when cooled. The substance will not glue materials sufficiently tightly.
The higher the cooking temperature of the glue, the faster it will be ready for use. For example, at 50 degrees, the solution should be cooked for 12 hours.
Adding lime to the solution of animal origin is unacceptable, since such an additive reduces the ability to glue objects. In addition, the mixture quickly deteriorates, molds and rots.
Varieties of glue from animal parts
Animal glue has many varieties and names: skin, skin, carpentry, painting, fur coat. They differ from each other in color and characteristics. Depending on the degree of purification, the color of the substance acquires a transparent, translucent, dark shade.
Animal skin glue
Skin glue is most resistant to rot, but only if it is well cleaned. To increase the shelf life, phenol, salicylic acid and creosote are added to the mixture. To achieve elasticity, glycerin, sugar, and even honey are added to the composition. Due to its low cost, animal glue is used as part of paints for painting and creating decorations. Also, such glue is added to the primer. Often it is used for gluing furniture.
Gelatin glue
Gelatin glue is obtained from the skins of young animals. The substance is produced in two forms - food and technical. The first type is completely colorless and is the most pure type of glue in composition. It is ideal for gluing those places in which the docking place should remain invisible.
The disadvantage of gelatin is its small bonding ability compared to glue from animal skin. One of its important advantages is its ability to be stored for a long time.
Isinglass
It is made from a swimming bladder of cartilaginous marine inhabitants (sturgeon and beluga). Domestic fish glue is considered one of the best in quality. However, due to its high cost, this type of glue is practically not used in technology.
A good grade of adhesive is obtained from pure gluten. It has excellent astringency and elasticity, and also has almost no color. Poor quality glue is produced from fish waste (scales, bones, intestines, skin).
Milk glue
Obtained from casein solution in combination with fats. Sometimes the main substance is replaced with skim milk, which, when dried, dissolves in water. To avoid this effect, it is enough to add caustic lime to the composition of animal glues.
This substance is used for the production of stretching soil, plaster, as well as for fixing patterns.
Casein glue
This substance is obtained after souring dairy products. To prepare this kind of glue, cottage cheese made from fresh milk, which is pre-treated with a separator, is ideal. This is necessary because in ordinary cottage cheese there are many bacteria, fat and sugar.
To obtain the purest casein in production, the method of artificial curdling of milk with acids (hydrochloric or acetic) is used. The resulting technical cottage cheese is washed with water, and then treated with soda or alcohol. The resulting glue is cured anew using acid. This process is carried out several times, until a pure product is obtained without fats, bacteria and sugars.
An important advantage of casein glue is the fact that it does not dissolve in water.
Apply it in painting, making mineral paints. Due to its ability to emulsify oil and resin solutions, casein is often added to the primer and tempera.
Animal adhesives in carpentry
Adhesives of animal origin include substances used in carpentry. There are several varieties of them - flesh, bone and mixed. Consider the production technology of these types of glue in more detail:
- Coarse glue is obtained from hides and cattle hooves. To clean the material from dirt and grease, the waste is immersed in milk of lime, washed thoroughly and boiled at a temperature of 90 degrees. The glue thus obtained is filtered and poured into dishes, where it is then evaporated and dried.
- Bone glue is obtained from the ground bones of animals. Fat is removed with gasoline. To get rid of particles of meat, bones are immersed in hydrochloric acid. Then the components are boiled until jelly is obtained, the resulting mass is cut into plates and dried.
- Mixed gelatin glue is obtained by mixing the skin and bone adhesives. In terms of properties, such a substance resembles a fish type of glue, however, mixed one is much cheaper in production.
Features of the use of wood glue
Glues in furniture production are used only in hot form. Before heating, the tiles for bonding parts are soaked for up to 8 hours in water, heating the water to 60 degrees at this time.
In carpentry, glue from animal bones is used of various thicknesses. The fact is that softwood needs to be glued together with a thicker composition, but the material from hardwoods is reliably joined using liquid glue.
If there is such a need, the glue can be diluted in water or heated too liquid substance to obtain the necessary mass.
Albumin Glue
Albumin composition is used in carpentry. It is obtained from the blood of a bull, which is first cleaned of foreign substances, and then dried by a special technology. It differs from wood glue with good moisture resistance, an easier method of preparation and excellent resistance to stress. This type of glue is used to produce plywood. Albumin glue with the addition of lime and ammonia is effective in use during wet bonding of wood.
Other types of substances that are used for gluing wooden structures:
- Glycerin glue is obtained by adding a small amount of glycerin to carpentry glue. Its positive qualities are resistance to heating, due to which it is used in places where temperature changes often occur.
- Cretaceous glue is obtained by adding some chalk to the wood glue. Due to the transparency of the obtained substance, it is used for gluing wooden structures of a natural color.
- Syndicon liquid adhesive is obtained by adding acid (acetic, nitric or hydrochloric) to its composition. Its scope is gluing paper, leather, wood and porcelain.
Glue quality
High-quality glue of animal origin should have a pleasant, not very pungent smell. Substances for gluing wood surfaces with a bad smell are rejected, since the process of protein decomposition was disrupted during the production of glue.
In a quality composition for the manufacture of furniture should not be acid and fat. The water content should not be more than 17 percent of the total mass. The outer film should make a loud sound when hit.
Glue recipe
To prepare animal and vegetable glues, it is necessary to soak small pieces of the necessary components in ice water for 12 hours. After this procedure, the liquid must be put on fire, while the temperature should not exceed 50 degrees. To prevent burning of the substance, special cooking utensils called a buttercloth are used. It consists of two pots of different sizes. A smaller one is placed inside a large vessel, then a large tank is filled with water and placed on the hob. A glue solution is poured into a small container. The result is cooking the substance in a water bath.