Cleaning Mold from Interior Surfaces

Visible mold growth must be removed before priming or painting. Cleaning mold is one part of this process.

Mold is a fungus that is eating the surface it is on and must be eradicated before any painting can take place, even before a surface is sanded. Sanding to remove mold will not work and probably will make the growth worse later by embedding the spores deeply into the sanded surface.

Bleach is used to completely kill fungus, either mixed with water or other cleaning agents. The use of bleach will cause premature fading and discoloration of the existing paint finish. There are two ways to clean mold, before repainting with a strong cleaning solution or for during regular maintenance after painting.

Cleaning Mold Before Repainting

When preparing a wall or painted trim for refinishing, producing a stable and clean surface is important. Since you will be repainting, removing mold with a heavy-duty cleaner, trisodium phosphate, and bleach will be appropriate.

To mix, add ¼ cup of trisodium phosphate, TSP, per 1 gallon of very warm water. Scrub the infested area and allow the TSP to sit on the surface for a few minutes. Rinse with warm water. Bleach can be added, 1 cup per gallon of TSP solution, for moderate infestations.

This will only remove mold and stains on the surface. Heavy deposits or growths will require an additional step. Since you are dealing with living microscopic organisms the use of a strong bleach and water solution will be necessary.

Mix the chorine bleach to water at 50% strength, a 1 to 1 ratio. Add this solution to a spray bottle. Purchasing a new hand sprayer is best; this will eliminate cross contamination with different chemicals. If using an existing sprayer, such as a window washer spray bottle, thoroughly rinse the bottle and pump with water to remove any residual chemicals.

Spray the mold contaminated area with bleach and water. Keep the area wet for several minutes, this will allow the bleach to soak into the pores and kill the mold. Allow to fully dry, and then prime with tinted shellac, alcohol based, stain-blocking primer.

Mildewcide additives are available and can reinforce the anti-mildew properties of all paints and will not affect the color or sheen. These additives are designed to inhibit the growth of fungus reducing the need to be constantly cleaning mold.

Maintenance

Occasionally cleaning mold from painted surfaces is necessary and repainting isn’t required or desired. Use a mild household cleaner with hydrogen peroxide, this is less likely to cause discoloration or a change in the paints sheen as compared to bleach.

Many products claim to be gentle on many finishes.

While cleaning mold, if using bleach is necessary use 1 cup of bleach to 1 gallon of water. Always test the compatibility of a cleaning product with your paint before washing a large area.

Apply some cleaning solution to a small inconspicuous area according to the manufactures directions and see if the original paint is affected.

Warnings and Precautions

Use caution and care when working with any chemical, especially bleach. When using a spray bottle a fine mist can be produced that could irritate your lungs. (Personal Experience)

• Never mix bleach with ammonia or acidic cleaners. A toxic gas will be produced.
• Wear protective clothing, eyewear and gloves.
• A respirator is recommended to protect your lungs from mold spores or the strong bleach smell.