Heat-treatment involves heating wood material to a temperature of 180 – 220 °C while at the same time protecting it with steam. The steam protects the wood, but it also influences the chemical changes taking place in wood. The treatment involves using only heat and steam. Thermowood® is an environmentally friendly and fully recyclable product, the manufacture of which does not include any harmful chemicals.

Heat treatment has an impact on several wood properties changing them permanently. The dimensional stability, decay resistance and thermal insulation properties of thermally modified wood are better than those of untreated wood. In addition, the wood is coloured throughout into a beautiful shade of brown. Heat treatment can be successfully applied to several types of wood. However, it is particularly well suited for pine and spruce. Thermowood® can be disposed of by incineration.

Thermowood® is almost always good to surface treat. However, this must be done according to the intended use. Suitable treatment agents for outdoor use are, for example, oils, wood preservatives or different paints. Varnish or waxes can be used in interior premises. They also provide protection against dirt and UV radiation. Untreated Thermowood® becomes lighter and grey due to the UV radiation from the sun.