
Digital Image

Digital Image
This powder room in the Medical Center area of Houston had a mirror glued to the wall. The homeowners want a different mirror, so had the original one removed. The mirror was attached to the wall with a tar-like substance called mastic. The glass guys use suction cups to clamp onto the mirror, then they pull it away from the wall. Some globs of mastic will be left on the wall, and this is a problem, because these tar-like substance will bleed through the new wallpaper.
So, to prevent any mastic / tar residue from bleeding through the wallpaper, the handyman took a Stanley knife / box cutter and cut out the top paper layer of drywall that had any mastic on it.
To smooth over the uneven edges, the handyman skim-floated the area with joint compound. The moisture in the joint compound caused the exposed paper inside the drywall to swell.
So what you are seeing in the top photo is a wrinkled section of drywall caused by moisture. This will show under wallpaper.
So I took a Stanley knife and cut out the handyman’s patch, to remove the wrinkled drywall paper layer. I sealed it with a penetrating primer called Gardz, which soaks in, binds surfaces together, and dries hard.
Once that was dry, I skim-floated over it (and the entire area), to get a smooth finish. Once my skim-float layer was dry, I sanded it smooth, and then primed again with Gardz.
The Gardz did its job, and did not allow moisture to penetrate into the exposed drywall, so no more wrinkles developed. See the second photo. Now the wall is nicely prepared and ready for wallpaper.