Heat-treated wood

What is heat treatment?

To obtain high quality sawn timber, the tree must be dried.

Until the mid-1990s, the most advanced technology was high-temperature drying at a temperature of 100 – 150 degrees Celsius..

In 1997, a new technology was introduced at one of the Finnish woodworking factories in Mikkeli, which was called <heat treatment>. With this technological process, drying is carried out at a temperature of 150 – 230 degrees. The higher the temperature, the greater the weight loss due to the evaporation of volatile compounds (in other words, the wood becomes lighter). The greater the weight loss, the less water remains in the wood. Depending on the conditions of heat treatment and the type of wood, the residual moisture content of wood is 40 – 60% less than that of conventionally dried.

The heat treatment process usually takes about 24 hours. The moisture content of wood after heat treatment is reduced by 80 – 90%. As a result, its heat capacity significantly decreases: heat-treated wood heats up much weaker than untreated wood, approaching in this indicator to abash. The surface of heat-treated wood is not porous, but dense, which significantly reduces the wood’s ability to absorb moisture from the air (by 30% – 90% depending on the temperature and drying time).

In practice, this means that wood is able to repel water without additional treatment with special impregnations. Heat treatment decomposes wood sugars, which are a breeding ground for microorganisms that contribute to wood decay. It becomes extremely resistant to decay, approaching in this indicator to larch, and, consequently, a hygienic material.

It should be especially noted that conifers almost completely lose resin, retaining a wonderful aroma, which increases with increasing humidity and air temperature..

During heat treatment, the wood changes color, acquiring a beautiful brown tint. It should be noted that the color change is through, which is clearly visible on the cut. Scratches on such a surface are almost invisible. By changing the heat treatment temperature, you can achieve the desired shade of wood and / or the degree of resistance to environmental conditions.

Where is heat-treated wood used?

Due to its beautiful appearance and unique properties of heat-treated wood, it can be used in many areas, including for interior decoration of saunas, for external cladding of buildings, flooring, both parquet and planks, garden furniture, boats, musical instruments, etc. P.

From the point of view of planetary ecology, as a material for benches in saunas and baths, heat-treated wood (including conifers) is a worthy alternative to the traditional abasha-sambo, which grows only in equatorial evergreens,, <rain> forests – the main source of oxygen in the Earth’s atmosphere, which cannot be restored. ”

What happens to wood during heat treatment?

  • Resin dries up or evaporates completely.
  • The color turns dark.
  • Thermal conductivity 0-30%
  • Surface strength increases.
  • The ability to absorb moisture is reduced.
  • Bacterial resistance increases.
  • Sensitivity to adverse environmental conditions decreases
  • The tendency to deformation is 30-90% lower compared to untreated.
  • The balance moisture is 10-50% less than untreated.
  • The cellular structure of the tree changes, becoming the same as if the tree had been dried for several hundred years.
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