strange paint bubbles/blisters?
We just moved into a stone colonial (house is 45 years old, previous owners were original owners) at the beginning of the summer, and I'm re-painting the DR in BM Nantucket Gray (latex ...the previous owners had painted with latex...the cans are still downstairs in the basement). Lightly sanded the walls with my favorite tool(Riobi cat sander) and wiped them down. No primer as the walls were in good condition.
Put one coat of the paint on, and in some areas there are little (1/4 inch?) blisters... in vertical lines (but not completely from floor to ceiling...scattered here and there) about wallpaper width apart. ?? Doesn't go all the way around the room, either.
There wasn't wallpaper on the walls...in the spot where the thermostat was I can see no evidence of peeled paint/wallpaper on the edges (same with the outlets).
Was there wallpaper a long time ago, and oil paint over that (or under that) that the previous owners then painted over with latex (but then why aren't the bubbles in more areas)? It seems strange that these little bubbles/ blisters would be vertically arranged, and spaced relatively evenly apart.
Recommendations? Husband thinks we should wait until the first coat dries (24 hours?) and scrape the bubbles, sand, then apply a primer. I am thinking Kilz? Then should we also prime over the Kilz?
And...I cringe to ask this, but can we scrape/sand in just the areas where the bubbles/blisters are? Would others Kilz over the whole room or just the scraped/sanded areas?
Finally, is there any way to test other walls in the house? I'd hate to Kilz everything in the house but if people think that's a good idea I'll just wrap my head around that. OH, and you really couldn't see any telltale "lines" before we painted the DR, in case anyone is wondering that.
Thanks in advance...love this forum!