Thermowood® can be surface treated normally. A better contact between the surface of Thermowood® and the coat of paint applied to it can be obtained by smooth-planing it or by brushing the surface. A fine-sawn surface is also well suited for surface treatment.
Because resin is removed, no knotting varnish is needed before applying the finish. Oil-based materials function just as they do on untreated wood. When using water-dilutable materials, it should be kept in mind that the water-absorption capacity of thermally modified wood is less than that of untreated wood. Water-dilutable surface-coating substances adhere to the wood surface very slowly when drying. Good test results have been obtained on UV-hardening paints and varnishes, and also on oils and waxes. When applying finishes to thermally modified wood the special instructions from the manufacturer of the finish used must always be followed.
As is always the case when applying finishes, attention must be paid to ensuring proper working conditions, temperature, moisture content and cleanliness of the wood surface also when putting the finishing touches to heat-treated wood.