Waterproofing wallpaper is often necessary in such rooms of the house as the bathroom or kitchen, as well as other rooms where excess humidity and moisture collect. To waterproof wallpaper one should apply coatings of water-based varnish, emulsion glaze or a primer to the wallpaper. The work should be done ideally in seventy degree temperature with little to no humidity (i.e., rainy weather).
Wipe down the floor of the room where you will be working from dust, dirt, and debris. This will prevent any breeze or draft from blowing these onto the wallpaper when drying.
Fix any repairs needed in the wallpaper, such as peeling ends, cracks; make sure that all joints of the wallpaper are firmly attached to the wall. All cracks between the walls, in the baseboard and the window frames must be filled, or else the varnish may seep between these cracks, drip behind the paper and cause discoloration. Apply two coats of weak glue to protect from stains from the varnish; let dry.
Wipe down existing wallpaper with mild soap and water to remove dirt and grease Let dry thoroughly.
Put on the gloves and respirator.
Prepare the varnish/emulsion/primer by mixing or stirring rather than shaking (this will avoid bubbling).
Apply the varnish with the brush; stroke with a fully brush and enough force to apply the coat evenly. Overbrushing will prevent the varnish from spreading and leave streaking and brush marks. Let dry for 12 hours.