The Consistent Production Principles of Thermally Modified Wood

The “Thermowood” brand is a patented trademark by the International Thermowood Association (ITWA). The rights of using this brand belongs to the association members only. The members of the Association are being Audited once a year by Finotrol which is an accredited third party quality control body.


There are two types of process types which are existing in the industry. These are called as “Open System” and “Closed System”.


Open System: The members of the Thermowood Association are the companies which own the Open System at their production facilities. The open system is generating the steam from the boiler system which is placed out of the chamber unit and the heat is being transferred through the radiators which makes the control of the heat of the wood in the chamber possible.

During the process, the wood gets Thermally Modified without deformation and the quality on each process can sustainably managed. The open system allows to measure the humidity, the surface temperature and the core temperature of the wood and the Relative Humidity in the chamber what means as having the control of the process during the production. Thus the control allows the continuity of high quality Thermal Modification and the structural changes in the wood rather than only changing the colour into a brownish colour.



Closed System: With a simple explanation the Closed system operates the kiln with heat flow generated by a burner. With this process the moisture content may be decreased and the colour changing may ocur on the Lumber. But big discolorations may be seen and different moisture levels may be reached after the process on each board. Becayse the closed system allows the control of the temperature in the kiln. The values of the wood in the chamber won’t have a sustainability with this process.



How do we call it? Thermo or Thermowood?


Attention: Only the members of the Association are allowed the Thermowood Brand where all the members own a Open System Chamber!

The Industry has two types of Heat Treated products in the market as “Thermo products” and “Thermowood Products”. The managable process which is the Closed System are being owned by the Thermowood Association members.

In our next article we will give you 4 key items to make the right choice for Thermally Modified Wood products.