See instruction “Facts and maintenance ash” under “Maintenance & installation”.
Oiled doors are not finished; they must be maintained as not to be discolored and ugly but also not to absorb moisture with swelling as a result. If the wood dries out, it absorbs moisture and swells. This causes the door to warp and there can be problems with both tightness and closing. Depending on the location of the door and the climate, the door may need to be oiled several times a year. A door does not turn as gray as wooden furniture or a terrace. The door is usually protected a bit by the roof at the top and retains its brown color but can become gray and black at the bottom where it is more exposed to rain.