Wallpapers add texture and decoration to walls. However, in rooms that receive a lot of moisture, like the bathroom, peeling may occur if the wallpaper is porous. In rooms with walls that see dirt and grime, like the utility room, porous wallpapers can stain. Seal porous wallpapers that are at risk of peeling or staining with polyurethane. As a plastic-resin, a polyurethane finish also creates an easy-to-clean surface. Use water-based rather than oil-based polyurethane, as oil-based polyurethanes can yellow over time.
Wash the wall with a solution of hot water and dish soap, wiping it down with a sponge. Contaminant-free wallpaper will ensure optimum polyurethane adhesion. Once clean, wipe down the wall with a sponge and plain water to remove the soap residue. Allow the wall to dry.
Open the can of polyurethane and stir it well. Pour a small portion into a separate container.
Apply a thin coat of polyurethane to the wallpaper, using a high-quality paintbrush or a foam pad. Allow the polyurethane to dry. Water-based polyurethane dries much faster than oil-based and should be ready for a second coat in no longer than three hours.
Sand the dried coat of polyurethane lightly with 220-grit sandpaper. Wipe away any sanding dust with a tack cloth.
Apply two additional coats of polyurethane, sanding in between.
Clean up tools and equipment used with soap and water.