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Interior: Troubleshooting

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  • Interior: Troubleshooting FAQs
No. Paints can be formulated to inhibit mildew growth, but under some conditions, mildew eventually will reappear on any type of paint.
Painting galvanized steel, like many other metal substrates, has its own set of "do's and don'ts" for ensuring a long-lasting paint job. Galvanized metal comes from the factory with a thin layer of oil to prevent white rust. Painting over this oil usually results in paint failure. Alkyd paints applied to galvanized metal produce an acceptable paint film initially, but will quickly fail. And when galvanized metal is allowed to remain exposed to the atmosphere, it will oxidize, producing a poor surface for coating adhesion.
Southern yellow pine has a tendency to contract and expand with weather conditions. In contrast, cedar and redwood are more stable lumbers, so paint coatings adhere to them better.
The most frequent causes for premature paint failure are as follows: insufficient surface preparation; low film build; improper coating was used; product not applied as directed; or environmental conditions (moisture, fumes, chemicals, etc.).
Latex paints contain chemicals called plasticizers that allow proper film formation and keep the coating flexible. Many vinyl and plastic weather-stripping materials also contain plasticizers to give them flexibility. When two surfaces containing plasticizers come in contact with each other, they can have the tendency to stick. This condition, known as blocking, will generally occur during the early curing time of the coating, but it can continue for some time. Blocking can also occur on double-hung windows and garage doors. The easiest way to prevent blocking is to use a non-blocking acrylic, or alkyd base paint in areas where it may occur.
The deposits, known as efflorescence, are caused by moisture in the masonry. The moisture dissolves salts in the masonry -- the mortar, block, concrete, etc. -- and is drawn to the surface by the heat of the sun. The water evaporates, leaving behind white deposits that must be removed before painting. After you find and fix the source of the moisture, remove the efflorescence with a wire brush and coat the surface with a masonry primer and topcoat.
The condition you describe sounds like an occurrence called surfactant leaching. Surfactants are surface leveling agents added to latex paints to improve its flow and leveling qualities. Under conditions of high humidity - in bathrooms, for instance - these surfactants can sometimes leach out of the uncured paint film. The resulting deposit usually looks like someone shook up a can of cola and sprayed it on the wall. Since these surfactants are water soluble, they can be removed by cleaning with a sponge and warm water. To prevent this from occurring again:- Allow more time for the paint to cure, with good ventilation, before exposing it to heavy moisture condensation.- Install and/or use an exhaust fan, vented to the outdoors, to prevent excessive moisture build-up. This will also lessen the possibility of mildew growth.
This problem is commonly called "alligatoring." The most common cause of alligatoring is the application of too thick of a paint film. The surface of the film dries first, with the rest of the film taking longer to dry than normal. When the underside of the paint finally does dry, it shrinks, causing the top of the film to pull apart and leaving unsightly cracks. You can prevent this by applying the paint at the manufacturer's recommended thickness and spreading rate. A less frequent cause of alligatoring results from painting over a contaminant on the surface such as oil, silicone, body oils, hair spray, etc. You can prevent this by thoroughly cleaning the surface before painting.
The most likely cause of the discoloration is the resin in the glue used to hold the wood together. An alkyd primer applied to the wood before the latex semi-gloss will usually lock this in, but sometimes you need to resort to an alkyd stain killer, or even a pigmented shellac stain killer in severe cases.

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