The colour change of Thermowood® is impacted by the treatment temperature and duration. The higher the temperature, the darker the colour. The colour change is primarily the result of the degradation of lignin.
Heat treatment colours the wood throughout. The final colour shade is a result of the combined effect of the treatment degree and surface treatment agent.
To keep the colour and protect the surface, the wood must be protected from the UV radiation of sunlight. Without surface treatment UV radiation will make thermally modified wood lighter and grey the same way as any raw wood material.
With coniferous wood, the uniformity of the colour is impacted by normal variations due to wood density and if it is spring or summer wood.
Colour of heat-treated pine using different treatment temperatures.