Cleaning and Sanding

It takes little time for the walls in your home to accumulate a thin film of grime, grease, and dust. And walls often look clean when they are not. Dirt and grime between the wall and the new paint must come off, because they will interfere with the adhesion of your new coating. If you think your walls are clean, dampen a paper towel with a little vinegar and gently rub a small place on the wall. You're sure to see the evidence on the paper towel that doesn't show up noticeably on the wall.

Phosphate residues weaken paint bonds, so use a low-phosphate household cleaner or brew your own with 1/4 cup of trisodium phosphate (TSP) in a gallon of water. Use the procedures discussed in "Good cleaning techniques," below.

Sanding walls provides a uniformly smooth surface with a slight "tooth," which helps the paint stick more securely. If you scrub flat or semigloss paints with a scrubbing strip, you have effectively wet-sanded them and won't need to go further. Glossy surfaces will need sanding with a 100-grit sanding screen.

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Good cleaning techniques

A thorough, effective cleaning depends not only on what cleaner you use, but also how you put it on. Because it's important to not leave cleaning residue on the wall, set up two 5-gallon buckets with two sponge floor mops (one needs to have an abrasive cleaning strip). Cleaning solution goes in one bucket, the rinse (1 cup of white vinegar to 1 gallon of water) goes in the other.

Map out imaginary sections in about 8-foot widths, sponge on the cleaning solution, and let it set for a minute, but do not let it dry. Immerse your mop in the cleaning bucket and scrub the section with the sponge. Then scrub the section again with the abrasive cleaning strip. This effectively removes dirt and opens up the old paint film so it will take new paint more readily. Rinse the section as soon as you have completed the second scrubbing and continue cleaning the remainder of the room in the same fashion. Change solutions often.

Washing a wall

Vacuum dust from the wall. Using a sponge mop with a cleaning strip, wash the wall with a low-phosphate cleaner or TSP solution. Work in sections, scrubbing each section with the cleaning strip and rinsing immediately with a 16-to-1 solution of water and white vinegar.

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Sanding a wall

Some walls need to be sanded, others don't. Flat or semigloss surfaces cleaned with a low-phosphate cleaner and scrubbing strip won't need sanding. Glossy paints will -- sand them with a sanding screen and wipe down the dust. In all cases, fix cracks and patch holes before sanding.

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What If... My walls are mildewed? Step 1

Mask off the baseboard and the floor area below the mildewed surface. Sponge on a 1-to-3 solution of bleach and water and scrub the mildew with a sponge. Let the solution set for 20 minutes to kill the mildew, keeping it wet during this time. Rinse the area thoroughly and let it dry overnight.

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What If... My walls are mildewed? Step 2

Using a high-quality stain-blocking primer or shellac-base sealer, prime the mildewed section and let it dry. The primer/sealer will keep the residual mildew from bleeding through the finish paint coats.

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