How to Paint Over Glossy Latex

Combine the tri-sodium phosphate and water in the plastic bucket, stirring until the TSP mixes with the water. Dip a sponge in the solution and wipe it across the walls, placing an even layer of the mixture on the wall. Leave the solution on the wall for at least five minutes.

Rinse the bucket with fresh water, removing all traces of the TSP. Add more fresh water and gently clean the walls with the new water. Dip the cloth in the water, rub it across the wall and rinse the cloth. After removing the TSP from the paint, wait 24 hours or until the water evaporates.

Sand the painted surfaces with medium-grit sandpaper. Rub the sandpaper over the surface, working from the top down. Work the paper over the wall, making sure that you rub the sandpaper over the entire area.

Rub a soft cloth over the wall, wiping off any dust sticking to the walls. As the sandpaper sloughs off the paint, dust sticks to the surface. Check the wall for any bumps or uneven areas and rub those out with fine-grit sandpaper. Wipe down the wall again.

Paint the walls with a primer designed for interior spaces or an outdoor primer, if the surface sits outside. The primer fills in any dents or dings on the wall and creates a smooth surface. When you paint the area, the paint sticks firmly to the primer, which hides the original gloss latex.