The final stage of wooden door restoration is the application of protective (conservation) coatings. The most resistant in operation are oils containing paraffin and varnishes.
Unlike varnishes, the oil penetrates deep into the structure of the wood without forming a film. Brush marks and various coating defects remain on the varnish layer, but with oil, especially if fast-drying oil is used, there is practically no sticky surface on which dust would settle.