I have an exterior slab that has tree sap and beer mug marks on it from leaving it outside for a couple of weeks.
I'm wondering if it is ruined for painting? The outer surface is like smooth paper, great after it is primed. But if I try to clean it I'm afraid it will fall apart like paper, and if I prime it I don't think the primer will stick to the stained areas.
What do you guys think?
Hi - Don't know about the beer mug marks but I bet the tree sap will bleed through most anything you put over it. Doesn't sound like you have much to loose here anyway so I would try cleaning it with 409 or similar, get as much tree sap off as possible. Scrape, sand, alcohol, whatever it takes, just don't completely soak it with whatever you clean it with, wet a rag/towel and clean as best you can. Lightly sand the rough spots and prime with shellac. Good Luck
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