Having stripped some wallpaper from the ceiling, I have ended up with some big patches where the plaster has come off. I have pva'd and repaired this with some multi finish and seems to have gone off / held ok but I wondered what the base was. Some kind of lime? It's a 1930 property.
The keying in the base it quite deep, some of the scratchings are 5+ mm deep which makes me wonder if it was a bit unsuitable for the multi finish which I applied in 2 coats.