We would advise that if you are hanging an external door that you use an oil based branded stain such as Sadolin or Sikkens woodstain. You must apply at least 3 coats to the interior and exterior sides of the door. All edges, hinge & lock cut outs must be treated to protect against water ingress.  If using an internal door you can use either an oil based stain or wax. Apply as per the instructions above. We do not recommend the use of any oils (e.g. Danish, Rustic) as this is a colourant rather than a preservitive. For any other questions please call our sales team.