Q: Can mildew be permanently prevented?
A: No. Paints can be formulated to inhibit mildew growth, but under some conditions, mildew eventually will reappear on any type of paint.
Q: I have a poor track record of success in painting galvanized substrates. What am I doing wrong?
A: 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.
Q: Sometimes paint doesn't adhere to Southern yellow pine. Why?
A: 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.
Q: What usually causes a coating to fail?
A: 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.).
Q: Why do doors painted with latex paint sometimes stick to the weather-stripping?
A: 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.
Q: What causes white powdery deposits on masonry surfaces, and how can I fix them?
A: 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.
Q: Within a week after painting a bathroom, yellowish-brown stains began appearing on the wall. For surface prep, we washed the walls with TSP and allowed them to dry for two days. We then primed with an oil-based product and added a high-quality semi-gloss latex top coat. The paint was allowed to dry for three days before anyone used the shower. What could be the problem?
A: 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.
Q: What causes small cracks to form on a recently painted wall?
A: 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.
Q: What causes frosting? How can it be avoided? What is the proper way to remedy it?
A: Frosting is a phenomenon caused when latex paint is applied in or is subjected to conditions that are too cold and/or too damp during the initial curing process. The lower temperatures and/or dampness do not allow the paint to coalesce, or form a proper film, which then exposes ingredients in the paint film to the elements. The ingredients that cause frosting are water-soluble sodium and calcium compounds. These are added to the paint to improve surface wetting, flow and leveling, and tint acceptance. When the paint film does not coalesce properly, these materials can rise to the surface, where they are exposed to moisture, usually combined with cool temperatures. When the moisture evaporates, a white "frosty" deposit is left on the surface. Frosting can usually be removed by flooding the surface with warm water. High-pressure washing is not necessary; just a lot of water to dissolve the material and flush it off the surface. To prevent frosting, always follow the manufacturers' application recommendations, but especially during the spring and fall when temperatures can drop drastically within the first 24-48 hours of applying paint.
Q: Why after one year am I getting discoloration on some areas of preprimed finger jointed wood-work coated with a latex semi-gloss?
A: 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.
Q: After a wallpaper liner is installed, do you have to apply anything more before you put on the paper?
A: If you are using prepasted paper, the answer is no. Just hang the paper following the manufacturer's instructions. If you are using paper with no paste, then you need to use an appropriate paste for the type of paper you are hanging.
Q: What is the procedure to remove wallcovering if the drywall was not primed before the initial installation? How do you prevent drywall from coming off?
A: This is a difficult problem that takes a great deal of patience and determination. You can reduce the damage by not over-soaking the wallcovering with the removal solution. After you remove the wallcovering, wash any remaining paste from the wall and patch any badly damaged areas, then apply a coat of high build primer-surfacer. This will uniform the surface much like a skim coat of plaster, but is a lot easier and less expensive.
Q: I paint the trim with a white alkyd semi-gloss, then come back a few days later and spray the walls with latex. Often, the white trim changed to a light cream color a few days after painting the walls. What's causing the problem?
A: This phenomenon is caused by a reaction between the additives in the latex that keep it from spoiling in the can with the drying oils in the alkyd. The yellowing cannot be removed, so you'll need to scuff sand and repaint. You can recoat with an alkyd after the latex is cured or use a top-quality latex semi-gloss. To prevent this problem in the future, apply the latex before the alkyd, or switch to latex semi-gloss for the trim.