Coating Choices for Exterior Wood Doors- clear coat for outside wood ,The Europeans prize their wood doors, and Sikkens developed a finish for that use. It also fails but does so in a way that allows easy maintenance. The Sikkens, as it ages, starts to look physically worn and thin. This is your clue to add another top coat. CleanUV-Protection Oil - Osmo UKClear UV Protection Oil 410 is safe for humans, plants and animals when dry. Clear UV Protection Oil 420 Extra is furnished with active ingredients to protect the coating against mould, algae and fungal attack. Microporous, penetrating finish which does not crack, peel or flake. No sanding necessary when topping up coating.