What is TMT
Thermally modified timber goes through a 3-stage kiln process which uses high temperature. It takes 24-72 hours to complete a full cycle. During the high temperature phase, the wood is protected from combustion by using steam. In that time, the moisture of the wood is almost completely removed and added back to a precise amount. The natural acids and sugars are modified from the extreme heat which changes the physical structure of the wood. The wood’s ability to absorb moisture is declined making it less prone to rot and decay. The equilibrium moisture content (EMC) of the wood decreases. This means the swelling and shrinking of the wood material due to moisture variations can be reduced by up to 60% as compared to unmodified wood. The most apparent change is that the wood darkens throughout, giving domestic wood the look of desirable imported wood.
The 3-phase process uses only heat and water to change a wood species ability to withstand the elements, making it one of the most natural, chemical free ways to extend the life of wood products.
The temperature in the kiln is raised rapidly to around 100˚C (212˚F), affecting the natural composition of the wood. Steam is introduced to prevent the wood from checking in the high heat. The moisture content of the wood is reduced from 15-20% down to nearly zero.
One peak temperature is resulting in a light cook, 190˚C (374˚F), and the other is the dark cook at 210˚C (415˚F). The higher and longer the heat, the darker the wood becomes throughout. At these high temperatures, the lack of oxygen within the chamber is what prevents the wood from burning.
Cooling & Re-Conditioning
Temperature is reduced by introducing steam. The steam cools and conditions the wood to a moisture content of 4-6% improving dimensional stability.