I started prepping the bathroom in my 1923 bungalow for painting. When I was examining the ceiling, which had several creases and cracks I pulled back one crack to see what was underneath and a large swath pulled easily away. My instinct is that what pulled away was just several years of paint, and I should try to peel the whole thing off, which seems like it will be fairly easy, and prime and paint fresh.

My concern is that I've diagnosed this situation incorrectly and there was some sort of protective layer of something other than paint. The peeled portion can still be glued back, if that is the case. The underlying material is very flat and is perhaps some sort of plaster or gypsum board, but definitely not of the sort with paper on the surface, like I'm used to seeing.

So should I peel away (taking precautions for probable leaded paint, of course) or glue it back and try to retexture all the cracks and creases?