Removing Mildew from Painted Surfaces

Mildew needs to be removed before painting. Otherwise the new paint will fail or peel as it cannot cling to the surface.
Professional cleaners use a variety of methods to clean mildewed surfaces. Some cleaners mix a chlorine solution, spray it on the surface and allow to dry without rinsing. This leaves the mildew spore in a powder form to remain. Other cleaners apply the chlorine solution and then rinse with a high pressure water spray to remove the dirt and residue. Finally, others apply a chlorine solution with a small amount of Tri-sodium Phosphate (TSP) or other commercial cleaner and rinse with a high pressure water spray.
The following formula can be used. However, it is hazardous to the eyes and irritating to the skin. If the solution has contact with the eyes wash the eyes with clean water and seek immediate medical consultation. The use of protective eye goggles is required. Extended exposure to this solution increases sensitivity and possible infection. Use a ladder to reach high areas to minimize exposure to the cleaning solution.
Water 64 ounces or 2 quarts
Tri-sodium Phosphate (TSP) 2/3 cup
Detergent (Laundry Soap, etc. ) 1/3 cup
Chlorine 5% (Household bleach) 64 ounces or 2 quarts
Place water in mixing container. Add the TSP and detergent to the water and mix till ingredients are dissolved. Add chlorine and stir mixture.
TSP is a strong cleaning agent to remove the dirt and fungus/mildew residue. Detergent aides in mixing of the TSP into the water and keeps the solid particles suspended till they are removed by the rinse spray. The chlorine is the ingredient which destroys the fungus/mildew spores.
The cleaning solution must not be diluted during application – apply at full strength. A garden pump type sprayer can be used for this application. The use of a garden hose sprayer using fresh water will dilute the solution decreasing the strength. The garden pump sprayers that are made mostly from plastic are preferred. The sprayer should be cleaned immediately after use otherwise any metal components will be corroded.
Any valuable plants should be protected from the cleaning solution. Plants should be watered with fresh water before cleaning and then rinsed with fresh water immediately after the use of the cleaning solution.
The painted surface must be dry before applying the cleaning solution to obtain maximum benefits. Any existing moisture on the surface will inhibit the penetration of the solution and also dilutes the concentration.
Apply the cleaning solution from the lowest level and work upwards. Spray an area about six to eight feet wide and move upwards to the top before moving to an adjoining area. Repeat procedure in the adjoining area. By working from the top down will result in streaking of the cleaned surface after drying.
The cleaning solution must remain wet for 10 minutes and not allowed to dry out before rinsing. Re-apply as necessary. Applying in shaded areas will prevent premature evaporation. In sunny areas re-wetting will be required.
While the surfaces are wet the optional use of a long handled brush, broom or sponge will aide in cleaning or dislodging dirt or debris. The mold/mildew will be killed even if this step is not performed.
Finally rinse with water till the surface has no remaining detergent (the slippery feel on the surface).

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