Here's the scenario: 92-year old house, every wall in house wallpapered. I'm removing wallpaper to paint and, although there are not a lot of cracks (a few hairline), the plaster is very bumpy. Some large bumps, some smaller (all smooth), but I'm afraid that when I paint, they'll show up really bad. They are solid. If you bang on them, they do not crumble or crack. What caused this (besides maybe a bad plaster job) and what should I do about them.....just paint over them and hope for the best?