How to Install a Glass Mosaic Tile Backsplash

While a porous surface such as new drywall or backer board offers the best bond with thinset, you can tile over a painted wall if you first rough up the surface using an 80-grit sanding sponge. If your walls are brightly colored and you're installing translucent tile, prime the walls with a sealer-primer, like Kilz, before sanding so that the color won't bleed through the thinset.