The sun’s ultra violet rays affect all wood, including heat treated wood. In order to preserve the golden brown colour the wood should be protected by waterproofing or by treating it with pigmented oil. If one chooses not to treat the wood against the sun’s rays the colour will slowly change to a beautiful silver grey tone.
If needed, Thermowood can be cleaned with a gentle cleaning product such as liquid soap. If the wood is very dirty one can use a pressure washer, but this should be done with caution. It is highly unusual that the wood turns blotchy, however should this happen it can be sanded in order for it to regain its original appearance.