A new coat of paint brightens dingy walls but it won't eliminate dirt and grease. Commercial wall cleaners, formulated for paint preparation, are available but you can save money by using common white vinegar. The natural acidity of vinegar breaks down dirt, oils and sticky residues, but it doesn't leave behind a residue that affects the newly applied paint.
Grease, stains and adhesives leach through newly applied paint, becoming more obvious over time. It's vital to thoroughly clean the walls before you begin to paint. Although a primer provides you with an even, unstained surface for applying the paint, dirt and bumps on the wall can still show through. Even a wall that appears clean can have a thin layer of dust or grease. Grease is especially common in the kitchen where the small particles adhere to the wall during cooking.
Vinegar provides a natural degreaser for walls. The residue of the vinegar won't affect the surface after it's painted. Soak a cloth in pure white vinegar and wipe down the walls. If the walls still feel sticky, you may need to soak the greasy area in vinegar to break down the oily particles. Soak paper towels in vinegar and press these against the wall. The wet towels adhere to the wall temporarily. Soak the greasy spots for 5 to 10 minutes then remove the towels. Wipe a second time with a vinegar-soaked cloth to remove any remaining grease particles.
Stubborn adhesive stains leave behind a bumpy surface, even after you cover them with new paint. Even flush adhesive stains can leach through the paint and show as new stains. Vinegar breaks down the adhesive from decals, wallpaper and stick-on hooks. Peel off as much adhesive as possible. Place a vinegar-soaked cloth on top the adhesive and hold it in place until the adhesive residue is thoroughly soaked. Scrub the area with a coarse cloth to remove the sticky residue. The area may require repeated vinegar soaking to fully remove the residue.
General Paint Preparation
Even walls that appear clean usually have a thin coating of dust or oily fingerprints that can later show as stains on the newly painted surface. Combine equal parts vinegar and water in a bucket. Wipe down the entire wall with the solution to remove the invisible grime so you have a clean surface for priming and painting. Dust also collects on top baseboards and trim. Wipe these areas with the vinegar solution before you paint. Dip a cotton swab in vinegar and wipe out decorative carved areas in the trim or in the corners so no dust remains.