I'm looking to clad an extension with Douglas Fir and would like to keep the colour [for as long as possible] I've contcated the likes of Ronseal but have not got answers. Effectively need a colourless uv treatment that will take over Vac-Vac preservation treatment. Timber will be stored until yellow of Vac-Vac fades. I then intend to treat the timber before its fixed to the building. Suggestions of potential solutions please!