You first need to seal new plaster to make it less absorbent and to help the topcoat adhere.
Sealing bathroom walls before painting.
Let the filler to dry then smooth down with a fine sandpaper.
Without primer the wall will tend to absorb coat after coat of paint.
Never really sealing the wall.
Previously painted walls do not usually require a primer but kitchen and bathroom surfaces have been exposed to high humidity which may cause the next coating to cover unevenly.
Unless the surface is chalky this will help bind the surface.
Finally sealing the painted bathroom tile protects your project from grime scuff marks and scratches.
If your walls are newly plastered here s what you need to know before painting over them.
Particularly important on new sheetrock.
Primer is less expensive than paint and seals the wall.
Definitely use a primer before painting new sheetrock and if you don t use a paint and primer in one.
6 apply the primer and sealer with a paint roller in a v shaped pattern.
Do prepare your work area before caulking the bathroom.
If the painted surface of the wall is flaking simply scrape the flaking paint from the wall.
If the plaster is showing after scraping flaking paint simply coat with a 1 part pva and 5 part water mix to bare plaster then face fill with quality filler toupret interior.
Clean the gaps with sugar soap before you fill as any dust could stop the filler sticking to the wall.
Apply low tack painter s tape to the walls at the edge of the ceiling to protect the walls from the primer and sealer.