To apply a sealant or primer to new plaster, it is important that the sealer must first be thinned properly for it to be absorbed by the plaster wall, and then it should painted onto the plaster wall just like a regular paint. The sealant may be a water-based paint mixed with water or an oil-based emulsion mixed with polyvinyl acetate, or PVA, adhesive.
New plaster walls and ceilings are highly absorbent, which means that if paint is applied directly onto its surface, it will absorb the moisture in the paint. This will likely cause the paint to bubble and flake off. Applying a sealant or a primer paint on new plaster will help paint adhere to the new plaster surface properly.
The following shows one method of painting on new plaster surfaces. Make sure that the plaster is dry enough before proceeding with the steps below.
Step 1: Clean the surface
Make sure that the surface to be primed is clean and free of dust, dirt and oil. Lay down old newspapers or cotton dust sheets on the floor to protect it from paint drippings.
Step 2: Mix the paint
Mix four parts of water-based paint with one part water. For bathroom and kitchen areas, use oil-based paint and mix it with a PVA adhesive using the same ratio.
Step 3: Add plaster sealant
Apply the sealant onto the plaster just like a regular paint. Listening closely, the wall can be heard absorbing the sealant. If not, the sealant should be thinned up a bit more.
Step 4: Apply the paint
If the plaster surface is dry enough, apply the paint desired.