Our ancestors knew an extremely simple and environmentally friendly method to permanently protect wood from environmental influences: thermal treatment, which requires no chemical additives whatsoever. The wood (ash) is specifically altered at 180–220 °C and essentially “caramelized,” resulting in a dark brown hue. During this process, some components of the cell walls (hemicellulose) are broken down, transformed, and recrystallized. The remaining elements fill the resulting voids. After this cellular transformation, the wood absorbs hardly any water. This is why it does not swell or shrink even when exposed to high humidity. And it loses its tendency to warp and crack. Thermowood is therefore an ideal material for items that frequently come into contact with water.