Jartek – recognised as one of the world market leaders in wood thermal modification equipment has honoured their 25 years of excellence in thermally modified timber section. Jartek thermal modification chambers guarantee a high-quality and consistent end product that meets the quality requirements of the certified ThermoWood® brand.
“One of our earliest thermal modification kilns was 70 meters long and needed an industrial hall around it: each process phase – high-temperature drying, thermal modification, conditioning and cooling – was separate from another. This spring we launched a mini ThermoWood® chamber that can process small batches of wood with a fraction of the original volumes”, says Timo Tetri.
A short look-back of ThermoWood® with Timo Tetri
Tetri was the first full-time employee to join Jartek’s thermal modification kiln business in the year 2000. Originally a project manager, Tetri has since acted as product, business development and operational manager – roles that led him to his current position as Senior Advisor. In the early years, he travelled the world looking for business opportunities for thermally modified wood in the US, Canada, South-East Asia, New Zealand and Europe. Today, Tetri is a sought after person at the office: people consult him on sales, business and project related questions.
He is also a long-time chair of the board at the International ThermoWood Association (ITWA), the members of which co-operate to enhance the use of ThermoWood® products. “Now that my career is at the end of its life cycle, my chair responsibilities will soon be taken over by Tuuli Luoranen, also chair of the board at Jartek”, he added with a smile.
The beginning of the wood thermal modification revolution
“In the early 1990’s, several large companies in the Finnish forest industry together with VTT Technical Research Centre of Finland were researching a new wood treatment method. The aim was to develop an alternative to chemical impregnation of wood and provide locally grown substitutes for tropical wood”, Tetri says.
This alternative was a thermal modification process that was designed to activate a natural reaction in the chemistry of wood itself with heat. A reaction that would help prevent the wood from decay and improve its technical qualities like dimensional stability and warping resistance. The end-product of this process is today known as ThermoWood®. The original patents for the industrial scale ThermoWood® process were granted to VTT Technical Research Centre of Finland. When the ITWA was established in the year 2000, members received a license to these patents, some years later the patents were purchased from VTT to benefit the members of the association.
ThermoWood® was first produced by pioneers in small-scale mills, catering to local market needs around the world. The first Jartek chamber was delivered to its customer in 1998. In the early 2000’s the association started controlling the quality of the ThermoWood® process worldwide.
After 2005, global production volumes started to grow. “In 2010, ITWA started a project to check if the process needed altering in any way. As it turned out, we were already doing the right things and things right. The members of the association produce ThermoWood® on an industrial scale and have seen tremendous growth in product demand since”, Tetri added further.
Understanding the delicate nature of the thermal modification process
Every species of wood reacts to thermal modification differently, so understanding how to optimise the process for different wood types is key. At Jartek, they are the only technology provider of ITWA. Their chambers guarantee the production of a high-quality and consistent end product that is sold under the ThermoWood® brand.
“The kiln construction has to be done carefully and the applications for each type of wood chosen correctly, to make sure that the material is suitable for its end-use and meets the quality requirements of the brand. The ITWA publishes a ThermoWood® handbook, making it easier to succeed in the manufacture and use of this wonderful material”, Tetri says.
A promise for the next 25 years of ThermoWood® with Jartek
The global production volumes of ThermoWood® exceeded 280 000m³ in 2024, when the volume in the early 2000’s was only 20 000m³. 99% of it is exported from Finland to 30-50 countries around the world. The most typical end-uses for ThermoWood® are external cladding, terraces, windows and sauna interiors, where they replace impregnated or tropical woods. In addition to ThermoWood® production, many companies also use Jartek’s thermal modification kilns to manufacture high-quality thermally modified wood that they market under their own brands, further showcasing the versatility and reliability of Jartek’s technology.
The use of thermally modified wood is likely to increase worldwide along with the general use of wood as a construction material. The growth in demand is due to more environmentally friendly choices made both in the manufacturing and end use of wood, and the ease of disposing of non-toxic materials compared to chemically treated ones. The association and Jartek as head of it promise to keep safeguarding the trademark and its reputation, and increase the usage of this beautiful wood material.
“Looking forward, I see enormous potential — especially as construction and design move toward more sustainable materials. Jartek’s strength lies in our ability to keep developing reliable, efficient technology while staying close to our customers. I believe Jartek will continue to lead this transformation — combining engineering expertise with a genuine understanding of what the market needs next.” – Tetri concluded.
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