FIXING FIBROUS PLASTER WITH CORNICE CEMENT (CORNICE BOND)
Mark cornice projection on ceiling at each corner of the room then mark a guideline with a chalk line or similar to ensure the cornice will be straight. Remove all wallpaper, loose paint and dust from where the cornice is to be fitted. Painted surfaces should be suitably roughened to provide a good key.
Cut internal and external mitres with a fine tooth saw using a mitre box. A butt joint will be necessary where the room is longer than the length of cornice. It is best to cut all cornice to the required length in each room and hold in position with temporary partly driven holding nails on the ceiling guidelines and underneath the cornice bottom edge – refer to diagram above.. Each length of cornice may then be taken down in turn (by removing the bottom nails) for the application of cornice cement.
Mix the cornice cement in a clean container. Using ½ litre of clean water, sift in 850g of cornice cement and leave to soak for about 2 minutes. Stir and mix to a smooth paste which should be stiff enough to spread on the back of the cornice without any tendency to run. It should remain sufficiently plastic to use for about 25 minutes from the time of mixing and set hard in about 1 hour. DO NOT OVERMIX – this will reduce working time. Quickly apply the cornice cement approximately 5mm thick and 20mm wide along the back edge of the cornice where contact will be made with the ceiling and wall.
Push the cornice firmly into position and hold on the guideline (Two people are required). Temporary holding nails can be used underneath the cornice. Excess cement may exude from the edges. This should be removed and used for stopping the mitres and joints or it should be discarded if it has started to stiffen. Finally, the last traces of cement should be removed with a scraper then wiping with a wet brush along the junctions. Remove the temporary holding nails when the cement has set