Things You'll Need
Paintbrush or foam pad
Polyurethane is available in a range of finishes, such as satin, semi-gloss and high gloss. Choose a texture that is best suited for the room and that will give the walls the desired look.
Ventilate the room you are working in by opening windows and turning on a fan to allow polyurethane fumes to escape.
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.
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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.
Mason Howard is an artist and writer in Minneapolis. Howard's work has been published in the "Creative Quarterly Journal of Art & Design" and "New American Paintings." He has also written for art exhibition catalogs and publications. Howard's recent writing includes covering popular culture, home improvement, cooking, health and fitness. He received his Master of Fine Arts from the University of Minnesota.