A.Bill Feist, a former wood-finishes researcher with the Forest Products Laboratory in Madison, Wis., and co-author of Finishes for Exterior Wood, responds: Many light-colored woods like fir can be self-primed (using the top coat as the first coat) with no problem. I wouldn't anticipate any adhesion problems as long as the original wood surface was properly prepared, and sunlight should not be a problem, as the acrylics are the very best resins for protection against UV degradation.

But if the door were to be fully exposed outdoors, you would need the benefit of a proper primer first coat (one recommended by the paint manufacturer for exteriors); in that case, I'd recommend that you strip the door and start over.

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