Another way to fix a heavy plaster centre rose is to seal the back of the rose with a watered down pva (unibond ect) because this is a very porous surface, use about 1 part pva-4 parts water and let this dry completely, this will take out the porousness of the rose, thus helping the adhesive from drying too quickly, which would prevent the adhesive from gripping the rose as it dries!
also if the ceiling is porous and a matt finish give this a coat of sealer as well,
now if you have a long batten that will reach from the floor to the ceiling, or some other set up like this it is possible by using either mixed texture powder or plaster/wall board adhesive, this must be of a thick consistency that does not run off your scraper as you pick it up, but not as stiff as you can't spread it.
Drill gently through the centre of the rose so that it doesn't crack, making sure that you can get the wires through
Check that the electricity is off
butter the base of the rose thickly so that when you offer it to the ceiling, gently apply pressure by twisting it onto the surface, this should make the excess adhesive squish from the edges, then set the wooden batten beneath it to hold into place, 8-24 hours if possible
fill around the edges with the excess adhesive and wash with a paintbrush or sponge
but check that the ceiling to take the rose has no distemper/limewash, flaky paint ect as this will need to be cured first of all
I hope that this helps
Regards
Dale
