While the properties of wood as a structural, load-bearing material are undeniable, Finnforest has pioneered a system which means the external appearance of a structure can be imbued with the natural warmth of wood as an aesthetic finish and protective cladding. Thermowood is produced by heat-treating Finnish-grown European redwood (red pine) to temperatures in excess of 200¦C. Withstanding such extreme temperatures causes chemical and structural alterations to occur in the wood, improving the material's basic durability characteristics. The internal stresses within the structure of the timber are reduced when it is treated in this way, meaning that the potential for twist and warp is reduced significantly - swelling and shrinkage of Thermowood are only 50 per cent of the corresponding values for untreated Nordic pine and are in a similar range to teak. A correlation in the decreased equilibrium moisture content and water permeability results in an altogether more durable timber that is suitable for exposed areas such as external wall claddings.