New wallpaper can be hung over existing wallcovering if it is adhering uniformly and is free of dirt, dust and grime.
Gently clean the existing wallpaper with a damp rag. Fill in and sand any cracks or holes with a fast drying compound filler. Paint the entire surface with a universal primer. To help conceal any visible seam separations, the primer can be tinted to closely match the background color of the new wallcovering. The pigmentation will hide background colors and patterns that may show through.
NOTE: If the old wallcovering is printed with metallic inks (gold, bronze, etc.) an application of shellac-based primed is required prior to application of a wallcovering primer. The shellac-based primer will seal the inks so that they will not bleed through.