CSLB C-33 Painting & DecoratingSurface PreparationMedium
A painting contractor is preparing an exterior wood siding for repainting. They observe areas of mildew growth, characterized by black, splotchy discoloration. What is the most effective and safest cleaning solution to remove the mildew and inhibit its return?
- AA commercial mildewcide cleaner containing sodium hypochlorite and detergents.
- BHigh-pressure power washing with plain water.
- CA mixture of household bleach and water.
- DAmmonia-based cleaner.
Show answer & explanationAnswer & explanation
Correct answer: A. A commercial mildewcide cleaner containing sodium hypochlorite and detergents.
Commercial mildewcide cleaners are formulated with active ingredients like sodium hypochlorite (bleach) and surfactants to effectively kill mildew spores and clean the surface, often with inhibitors to deter regrowth, while being safer than pure household bleach.
Why the other options are wrong
- B. Power washing with plain water may remove surface mildew but does not kill the spores, allowing it to return quickly.
- C. While bleach and water can kill mildew, household bleach alone can be too aggressive, potentially damaging wood, and commercial products often include surfactants and inhibitors for better results.
- D. Ammonia is not effective against mildew and can be hazardous when mixed with other cleaning agents.
Mildewcide Cleaner
A cleaning solution specifically formulated to kill mildew and mold spores, remove stains, and often contain inhibitors to prevent future growth on surfaces.
- Contains fungicides (e.g., sodium hypochlorite) and surfactants.
- Safe for various surfaces when used as directed.
- Essential for preventing mildew recurrence before painting.
Memory trick: Don't just wash, kill the mildew with a cleaner, then paint it new.