Kill the Stains
After removing some glued-on paneling, my husband sanded every inch of the walls to smooth out the glue ridges. Then we had someone texture the walls before we painted. The end result was beautiful—until the old glue lines bled through. Please help! Andrea Hardman, Kent, Wash.
John Dee replies: First you'll have to seal the stains with something that really works: a clear, dewaxed shellac such as Zinsser SealCoat. Brush on three coats—shellac can be recoated within 30 minutes and you don't have to sand between coats.
Next, apply an interior oil-based primer/sealer over the shellacked areas. This reduces the chance of "flashing," or having uneven areas of gloss show through the final paint layers.
Finally, before you repaint, I'd strongly recommend coating all the wall surfaces with an all-purpose alkyd primer just to make sure none of the primed areas will flash.