Mildew is a common problem for our customers. A bit of understanding as to how it forms will avoid considerable frustration.
Mildew is an airborne spore carried by air currents, insects. Their food sources include wood, pollens, bacteria and dirt. They also need moisture and oxygen. They do not feed on good quality paint or stains.
Mildew can be tough to detect as they are microscopic in their early stages. As they grow (colonize) they become visible, usually as black dots. If the wood is continuously wet, algae may form. Algae is a plant form and green in colour.
As mildew grows, it increases in bulk and can push apart coatings such as a topcoat from the previous coat. Proper cleaning is always worthwhile. The signs of this problem on a failed coating is the presence of mildew spores on the underside of the peeling paint.
Excessive moisture from either inside the house or outside, will encourage mildew growth. A layer of dirt and food such as pollen, on a coated surface can also provide an ideal environment for mildew growth. Dirt attracts moisture and therefore all requirements for mildew growth are present.
If mildew starts growing on a painted surface, a mild solution of bleach and detergent will clean away the spores. If the mildew is between coats of paint you must remove the topcoats to get at the mildew colonies.
Another reason to always lean before you paint.
