My previous post talked about smoothing a textured wall, so that the new wallpaper would have an intact surface to hold on to, and so that ugly bumps would not show under the new paper. I did the same thing today, in a large powder room with 10′ high ceilings, in a new home off Fannin, south of Loop 610 in Houston.
Once the walls were sanded and wiped free of dust with a damp sponge (rinsed frequently) (a crucial step, because any dust left on the wall can, when paint or primer or wallpaper is applied, delaminate, which means to pull away from the wall, which results in curling or loose seams on the wallpaper).
Anyway, once the walls were wiped and then dried, I rolled on a primer. While I use different primers for different situations, when I have newly floated walls, as in this case, I like to use Gardz (see photo). Gardz is thin and watery and soaks into porous surfaces, such as the thirsty joint compound in this newly smoothed wall. Then it dries very hard and solid, binding everything together, and doing a super job sealing the surface.
It also lends a wonderful surface for wallpaper to adhere to.
In the photo, the areas that are white are unprimed, and where the Gardz has been applied but has not yet dired, you see grey. When the Gardz dries, it will be clear. The surface will look a little irregular, because you see white areas where the join compound is thicker, and the paint color where the joint compound is just thin enough to skim over the high points of the textured wall.