Using the right gilding size is very important, normally the Instacoll Gilding Size gloss (the matt is for indoor only) is for porous and non-porous surfaces, interior & exterior when gilding with genuine gold leaf. For gilding with imitation gold, silver, copper use Permacoll Gilding Size but for interior only. For general gilding with imitation gold, copper and silver on wood use Nazionale Mission gilding size. For special gilding projects, read Choosing The Right Gilding Adhesive.