A.Myron Ferguson, a drywall
contractor in Broadalbin, N.Y., and the author of Drywall:
Professional Techniques for Walls and Ceilings,
responds: Sunlight — as well as the mere passing
of time — will cause the paper face of drywall to yellow
or turn darker, a process that begins in less than a week if
the drywall is exposed to direct sunlight (see photo).
The color typically bleeds through the compound when seams are
taped, and it also bleeds through latex paint.
Seams and fasteners that were taped before the surface turned
yellow usually stay whiter, so the newly painted surface
If a wall or ceiling is not going to be finish-painted soon,
it's a good idea to apply a coat of primer over the newly hung
drywall, whether it is going to be taped or not. This will
prevent the yellowing of the drywall's face paper.
In your situation, you should begin by removing any loose tape,
then sand the surface to remove cobwebs and dirt, and maybe
even wash the walls and ceiling with a damp sponge before
repairing and finish-taping the drywall.
Next, prime with an oil-based or shellac-type stain-blocking
primer; I like to use Kilz (Masterchem Industries,
866/774-6371, www.kilz.com). Since this oil-based primer
raises the nap on the paper, you will need to lightly sand the
surface when it's dry.
You can then use a latex finish paint over the prime coat, but
be sure to give the primer plenty of time to dry first.
Also, when you apply the finish coat, make sure the humidity
level is low and that there is plenty of air circulation so it
will dry quickly; this will help prevent any more bleeding