The patented ThermoWood® process guarantees high and stable quality

The roots of the thermal modification are in the studies in 1930s and 1940s in Europe and USA. There were only test batches and manufacturing process never reached an industrial scale. Decades later, VTT (Technical Research Institute of Finland) became interested in thermal modification and as a result, the Thermowood process was patented. The trademark ThermoWood^® was launched at the end of 1990s. The trademark is owned by the International ThermoWood Association (ITWA) and we are one of its founding members. ITWA has published new ThermoWood Handbook in April 2021.

Patented process

The founders of Lunawood, Aulis and Olavi Kärkkäinen co-operated in the research and wanted to utilize the patent in industrial scale from the beginning.

The patented production process is based on the gradual thermal modification of the wood, wherein the chemical and physical properties of wood undergo a permanent change. Thermal treatment means that the process itself uses only steam and heat; no chemicals are used in the process.

The patented ThermoWood process

Heat inside the thermal modification chamber, kiln, is slowly raised up to 212°C and the whole process can last 2-4 days depending on the wood specie and dimension. Water is needed for two reasons: because the temperature rises so high, water prevents the wood from burning during the thermo-treatment cycle. Water is also used to ensure the quality of the final product. Namely, the final moisture is added to the product to prevent cracking and ensuring long life. When the process is complete, the moisture percentage of the raw material is around 4 – 7 %.

ThermoWood^® – certified quality

Thermal modification can be done in many different ways and for different wood species. Not all processes follow the patented manufacturing method of ThermoWood^®, not all processes are standardized. Ours is!

Addition to external auditing we do continuous quality control by ourselves in our laboratories. 

Lunawood produces trademarked Thermowood products by a patented and annually audited process. Our production process is audited three times a year by an external 3^rd party auditor. In addition, we carry out continuous quality control ourselves, as we take 10 samples of each kiln load and test them in our own quality control laboratories in Iisalmi and in Kaskinen in order to ensure our high product quality for our customers.

International ThermoWood Association (ITWA) has published new ThermoWood Handbook providing the essential information on thermally modified wood products, objectively and comprehensively.