Don't noWas it silk paint on wall
Hard plasterUsually if it's silk it's got a shiny surface and I usually score it with a wallpaper scorer or even a Stanley knife is it hard plaster or plaster board behind
No party wallStrange any sign of damp is it an outside wall I mean like a wall that faces the outside of the building
10square metresthe paint as not keyed to the background. the emulsion was either applied to lime wash, distemper. or the paint was applied without a colour wash, i.e. to thick .
how large an area has not keyed ?