I am preparing to paint a drywall ceiling and find that at each nail there is a dark smudge. This is not a nail pop. Any ideas what caused them and can they be painted over without stain block?
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Rusted nail heads?
Do it right, or do it twice.
Perhaps the nails were cooled by a cold space above (Under-insulated attic?) and water condensed on those spots, promoting the growth of mold. Try a bleach solution to see it you can remove the stains. Wear eye protection and rinse before painting.
Al Mollitor, Sharon MA
Thanks for your suggestion. Since the space above the ceiling is inaccessible, if the bleach gets rid of the mold would you guess that if I put exta mildewcide in my ceiling paint the problem won't recur for a few seasons. While not a perfect solution, it would be good enough
brucemd,
Gotta agree with ELCID on this; don't think bleach will fix it.
Gouge out the mud and take a gander at the worst nail head.
If it's rust, you need to shoot 'em with Kilz or another stain blocker. They have one that shoots straight up for just this sort of thing, (brand name...'Upshot'??). Try a professional paint store.
Now, if this turns out to be the case, the primer spots will flash through the new paint. Lightly sand the primer spots and hit 'em with a few coats of paint/PVA split coat. Then hit the whole ceiling with the same. Then paint.
Hope this helps.
skipj
skipj:
After the stain blocker and a light sanding, what are the subsequent steps. Not familiar with what you mean by paint/pva split coat. Then the paint/pva must be used over the entire ceiling and then a "normal" latex or acrylic paint top coat. That's a lot of steps, but since it's my mother-in-law's ceiling short cuts are not allowed. Thanks for your help.
does your MIL smoke?
if so, it's just smoke stains attracted to the higher moisture at the screw or nail heads. No need for all the other buzz above.
Excellence is its own reward!
I've think I've seen that in a house where the woman burned scented candles all the time.
I'll be damned, you learn something new every day.
I think we may have solved the problem. My mother- in-law did use scented candles in the room where the staining occurred. In other rooms with the same ceiling/insulation configuration no staining occurred and no candles were burned. So I will try the easy solution first, i.e. wash the effected areas with tsp. There is one nail pop, so I will dig that nail out to determine if there is any rusting. If there is none then I will have some confidence that we found the right solution. I want to thank you and all others who took the time to help out. Both me and my mother-in-law thank you.
Yer welcome. All credit to piffin on this though, his post just knocked a few memory cells loose in my brain case.
brucemd,
It occurred to me after I posted that I should have defined some terms. So here goes:
Flash: The use of a solvent based primer will change the porosity of the ceiling in the areas where applied. This will cause the primed spots to appear shiny compared to the rest of the more porous ceiling. (Hence: "Flashing".)
Lightly Sand: We're talking 220 grit. Don't break the stain primer's integrity.
Split coat: 1/2 PVA (Poly Vinyl Acetate, box store translation: Drywall Primer. Buy the most expensive one, higher solids.) 1/2 finish paint. This allows you one coat finishing, as PVA is white, and if you mix in the finish color, you can usually get away with one fonish coat.
Coating the entire ceiling with split coat: This is an attempt to even out the porosity of the ceiling. You'll be able to tell after the first coat dries. If the primer spots flash much, put on another split coat.
Main thing is to check the nail heads.
My sympathies on the MIL situation. Just paid some of my guys to move mine. Again.
skipj
If the problem is caused by moisture starting at the pointed end of the nails, then all these proposed solutions are just temporary. Might be time for major surgery...remove all of the discolored nails and replace (in new holes) with stainless screws.
Do it right, or do it twice.
I always scrub any interior paint surface with a TSP (tri-sodium Phosphate) solution before painting.
Rinse after the scrub. It removes stains and smoke and mildew and etches the surface for a better mechanical bond.
Excellence is its own reward!
piffin,
Don't know about your State, but in some the TSP package looks exactly the same, but the fine print tells you that it is a "Totally Superior Product" which contains, (drum roll), NO PHOSPHATES.
Fine print reading, (can be ), it's own reward.
skipj
alcohol based primer will take care of it every time.