Cleaning a wall before painting it can be either a quick job or a major effort depending on the condition of the wall itself. Cleaning the wall before applying a new coat of paint always means more than just a simple washing down with warm water if you really want to make sure the job is done right.
Cleaning a Wall Before Painting
Remove any peeling or chipped paint with a putty knife. If the paint is willing to come off without a lot of effort, go ahead and remove, but don't force any paint from the wall that doesn't need to be removed. Sand down raised areas of paint to blend in with those areas where the paint has been removed.
Clear away any plaster that has become loose. Use spackle to fill in cracks and holes. You should able to use your putty knife to apply the spackle, but if not, then use a blade large enough to do the job. Sand the spackled area smooth. Use a lint-free cloth to remove dust that was produced by the sanding process.
Use a duster or dust mop to wipe away areas where cobwebs might have formed. This is an excellent method for cleaning away dirt and dust that could get beneath the paint. Make sure to clean the corners from top to bottom and edges where the ceiling and wall meet.
Prepare a mixture of warm water and a mild soap detergent. Place newspapers on the floor up next to the wall. Dip the sponge into the bucket of soap and water and begin cleaning from the bottom of the wall, working your way up. This strategy is recommended because the water will run down the wall as you clean it and streaks over soiled areas are much more difficult to remove than streaks running down an already cleaned wall.
Rinse with pure water and then pat dry with a towel. Make sure you have plenty of towels for drying because you want them to be as clean as possible for each section you dry off.