I moved into my 1913 home two years ago and painted the living and dining rooms not long after moving in. This summer a number of hairline cracks appeared on the ceiling and a few walls. This being Minnesota we had the usual freezing winter and steamy summer--real extremes of weather. We also pulled out some very painted-on windows in these rooms for sash repair earlier this summer. I assume one or both of these things caused the cracks. The question is how to repair them? They are truly hairline cracks--it really seems like just the paint has cracked open a tiny bit. The plaster on both sides of the crack is all quite secure. So I don't see any need to gouge them out/deepen them to fill, or any need for tape. I'm thinking that I could just rub a tiny bit of flexible caulk in them with my finger, prime and paint. Or maybe skip the caulk and just prime and paint. On the other hand, I could just pretend they don't exist (nothing exists these days if I don't have my distance glasses on!) and check back in a few months to see if they've grown. Any opinions?