Professional painters use mild detergent and warm water when washing walls prior to painting for the best results.
Warm, soapy water is usually your best bet. Fill up a bucket and use a sponge to gently rub the wall, starting from the base and working your way up. This should get rid of the bulk of dust and grime on the surface, and you'll end up with a much smoother wall for paint application.
Professional Painters Usually Don't Wash Walls.
In addition to smoothing out walls, painters may also do a bit of cleaning, remove stains, tape over trims in the room, and remove outlet covers.
A Chemical Clean
Use a commercial cleaner such as Trisodium Phosphate (TSP) to make sure everything is deep cleaned. TSP removes dirt, grime, scuffs, soot, and all other manner of soiling.
The wall cleaner you'll use is safe, effective, and readily available—all you need is dish soap and salt. The dish soap cuts through grease and dirt while the salt acts as an abrasive to remove stains and grime. Combine one cup of dish soap and one cup of salt to mix a thick, gritty paste.
Stick with Warm Water or Mild Soap
Glossy paint: All-purpose cleaner or dish soap and water. White paint: Baking soda and water. Latex paint: Dish soap and water, or vegetable oil-based cleaner. Oil-based paint: White vinegar, or dish soap and water.
Wipe down walls before painting
'Wash the walls to be painted using circular motions before rinsing with water,' says Andre Kazimierski, CEO, Improovy Painters Hinsdale. 'It's important not to use too much water, and to allow walls to dry completely before painting.
You probably don't need a primer. If the current wall is smooth, clean and covered with the same type of paint (both are oil-based for example), you can head straight for the paint. You need to fill holes, spackle and sand*, maybe even cut a new piece of drywall in to the existing wall.
No matter what type of paint you have on your wall, fill the bucket about halfway and never use more than a couple drops of dish detergent. Some alternatives: castile soap instead of dish detergent, a microfiber cloth instead of a sponge, and a long-handled, soft-bristled brush for hard-to-reach places.
You can paint over a dirty, glossy, chipping, and flaking surface, but don't expect your handiwork to hold up over time. For new paint to stick, your interior or exterior surface needs to be clean and free of dust that could interfere with your paint's ability to adhere to walls, trim, and ceilings.
The vinegar and water solution alone is great to use for washing walls before painting as well as routine wall washing in the home. *Note, if you need a little extra scrubbing action switch from the smooth side of the cloth to the scrubbing dots side.
While there is no best way to clean walls before painting, most walls can be washed using a sponge and warm water. For surfaces that have exposure to oil or grime, like kitchen walls, wash with a solution of water and grease-cutting detergent and follow up with clean water to remove any residual cleaning agent.
You can quickly clean smooth-surfaced walls with a wet Swiffer mop. It can touch hard-to-reach spots on the wall and slides easily along the corners. The primary downside is that fresh Swiffer pads can leave drips, which can leave marks and get behind outlets and light switches.
After pressure washing your house, you have to wait for it to fully dry before you can paint it. This waiting time can be anywhere from 24 hours to 3 days. Pressure washing isn't for beginners. If you're not experienced, the high water pressure can easily damage portions of your house's exterior.
Because it is acidic, full-strength white vinegar can be damaging to painted walls while oil-based paint finishes should never be cleaned with white vinegar as it can cause discoloration. Flat finishes, on the other hand, can be cleaned with diluted white vinegar (approximately 10% vinegar mixed with 90% water).
Rinsing is not necessary! If you're simply using a vinegar and water solution to wipe and disinfect, you won't need to rinse. However, if there's also plenty of dirt and grime you're wiping away, you may also want to rinse with some extra water.
You can also use most non-abrasive multipurpose cleaners on this type of paint or make your own by mixing one teaspoon of liquid dish soap and ¼ teaspoon of white vinegar into one quart of water. This cleaner should work on most latex paints. Finally, oil-based paints can take a slightly stronger cleanser.