Impregnation is the saturation of wood with various substances that are designed to protect this material from moisture, mold and weather conditions. The first information on the impregnation of wood dates back to the times of Ancient Egypt, when the most valuable wooden products were impregnated with cedar oil. For many centuries, animal and vegetable oils were used for the impregnation of wood. In the 19th century, inorganic salts soluble in water (salts of fluorine, arsenic, chromium copper) were used for this purpose. Depending on the purpose of the wood, different methods of wood impregnation are used.
This method consists in impregnating the wood with a brush, brushes, rollers and a cloth. For the wood to be effectively protected against external factors, it is necessary to apply two layers of impregnate. The second layer is applied after the first one has dried. Usually one layer dries from 1 to 3 hours.
Impregnation of wood by spraying is carried out using a spray device. Here, too, two layers of the preparation are necessary to thoroughly impregnate the wood. Spraying of the impregnating substance takes place under pressure, but the absorption itself is a non-pressure process. Due to the toxicity of the substance, it is necessary to take precautions when spraying wood.
Watering impregnation takes place in special tunnels. Wooden elements are placed on roller conveyors and thus moved along the tunnel, where they are coated with impregnation. To avoid toxins escaping into the atmosphere, the room in which the water is sprayed must be sealed.
4. Hot bath.
It is the protection of wood against external factors by immersing it in the impregnating agent. This process takes place in chemically resistant baths with covers, at a temperature of 200 ° C and lasts from 30 to 180 minutes. This method allows obtaining surface and deep impregnation.
5. Cold bath.
This method involves immersing the wood in a cold impregnation and leaving it there for up to eight days. The penetration depth of the preparation is from 10 to 30 mm.
6. Hot-cold bath.
It is a combination of the two methods mentioned above. Alternately, a hot bath is made in a solution of salt impregnate (temp 60-700 * C) and in a cold oily solution (temp 80-90 * C). This is a very effective method of wood impregnation, because during heating the air contained in wood expands and escapes to the outside, while during the second stage, the cooled material together with the shrinking of the air contained in it causes absorption of an additional amount of impregnation.
7. Osmotic (diffusive) method.
It is a method of impregnating trees that have been recently felled. Before impregnating wood, it is necessary to debark it, then the wood is greased with paste and covered with a tarpaulin. After 3-4 months, the wood should be cleaned and dried. The diffusion process involved in it made the preservatives penetrate deep into wood at 30 mm.
8. Low-pressure methods of wood impregnation
This method consists in impregnating the wood with impregnation using a low pressure. The wood is placed in a sealed device and impregnated with a low pressure produced by the compressor. Another method is to hang the tank at a height of 10-12 m above ground level. In the initial stage, the juices leak out of the wood, then the log is filled with impregnation. Currently, this method has been discontinued on an industrial scale, it is used rather in small enterprises. When using this method, precautions should be taken because it is very toxic to the environment.
This method of wood impregnation consists in closing wood in an airtight cylindrical or cuboidal container. Then the pressure is lowered to 16 kPa and maintained for about 15 minutes. The next step is introducing the impregnation and pressure equalization for about 60 minutes.
10. High-pressure methods of wood impregnation
This method is used for deep impregnation, it is most often used for wood intended for difficult conditions, eg permanently exposed to atmospheric conditions.