How to prime over old paste?

Removing old wallpaper can be challenging and even after all the paper is gone stubborn paste can remain. Old paste can interfere with the adhesion of your new paper. It is important to remove as much paste as possible before reapplying wallpaper. Most paste should come off with a sponge and hot soapy water. You can also use wet medium-grit sandpaper to remove any paste residue.