What is wood heat treatment and why it is important
We often hear about the heat treatment of wood, without fully understanding its importance. This operation is in fact essential to prevent attacks by pathogens, which in the long run could compromise the stability of a piece of furniture or a wooden shelf. But how is the heat treatment of wood done and how does it change its physical properties? To fully understand the benefits deriving from heat treatment it is important to make a premise.
Advantages of heat treated wood
Insects and lignivorous fungi are attracted to wood because they find water, oxygen and sugars in it. Their devastating effect compromises the stability of the structure. When we manage to eliminate even one of these three elements we will have practically eliminated the risk that the structure can be attacked by parasites. One of the methods used to poison food that pathogens find in wood fibers involves the use of chemicals, such as boron salts, creosote or copper sulphates: effective products but which do not poison only the sugars present in the wood . In fact, these products are also toxic to humans! Is there another way to have unassailable materials without using harmful products? The answer is called heat treatment.
But this is not the only advantage that thermally modified wood (conventionally treated wood is called thermowood) allows to have. In fact, the heat-treated material, in addition to increasing durability and stability, is light, resin-free, pleasant to the touch, with a very low probability of deformation or twisting, aesthetically perfect in its splendid dark shade, and totally free of chemicals.
How to carry out the vacuum wood heat treatment
As already mentioned, the heat treatment of wood is a completely natural process, which is performed inside special bivalent cells to perform drying and high temperature treatment. The wooden material is then dried first and the level of humidity present inside the wood drops to almost zero.
At the end of this first phase, we proceed with the actual heat treatment. The wood is subjected to temperatures that can be between 190 ° C and 210 ° C (depending on whether you want to obtain a product intended for internal or even external use). At these temperatures the wood undergoes a chemical change, and the sugars present in the cells change and stabilize the shape of the cell itself. Once the desired level is reached, the temperature is kept constant for 2/3 hours, before proceeding with cooling. In this phase the high heat could generate fires and it is for this reason that the chambers in which the high temperature treatment is carried out provide for vacuum processing, i.e. in the absence of oxygen.
We have thus reached the last phase of the heat treatment, the one that involves cooling and, depending on the wood species treated, the restoration of humidity. Thanks to a system that does not use water, the temperature is lowered up to 80/90 ° C and the percentage of humidity it needs for use is returned to the wood by means of steam, i.e. around 8%. This minimal presence of humidity will serve to make it more easily workable later.
The thermo-treated wood is ready for use and can be used anywhere thanks to its technical properties which, thanks to this process, have become optimal and durable over time.