When painting doors or woodwork, the paint of choice is often a gloss paint. Additionally, bathroom walls often have a gloss paint covering them. When you wish to paint over gloss paint, take the time to prepare the glossy surface first before you apply any paint. If you do not properly prepare the surface, you may find that the new layer of paint does not adhere to the glossy surface.
Mix 1/2 cup TSP with 2 gallons of warm water in the bucket. Apply the TSP mixture to the gloss paint surface using the sponge. Cover the entire area evenly with the TSP and allow the TSP to sit on the surface for two minutes.
Fill the bucket with plain water and use the sponge to apply the water over the surface to rinse away the TSP. You may need to rinse the surface more than once to remove heavy soiling. Allow the gloss surface to dry completely.
Rub the medium-grit sandpaper over the wall surface to produce a scratchy surface over the gloss paint. Work evenly to make every inch of the gloss surface scuffed and scratched.
Wipe the wall surface with the tack cloth to remove the dust. Alternatively, you could also vacuum the surface with a vacuum cleaner and brush attachment.
Apply a primer over the gloss paint to match the paint you will apply. If you will apply an oil-based paint, apply an oil-based primer. Use a latex primer if you will be applying latex paint.
Paint the surface after the primer dries completely.
Using TSP helps prepare a surface by deglossing the surface. This is particularly useful when you wish to paint over gloss paint. TSP also cleans the surface, removing dirt and other debris from the surface before you paint it.
Wear gloves as you work with the TSP to protect your skin from this chemical.