A number of readers have asked about problems with painted surfaces. With assistance from the Paint Quality Institute in Spring House, Pa., we offer ways to deal with some of the more common issues:

Blistering. Bubbles can result when paint doesn't adhere properly in some places and lifts from the surface.

Possible cause: painting a warm surface in direct sunlight; moisture escaping through exterior walls; or exposing latex paint film to dew, high humidity or rain shortly after the paint has dried, especially if there was inadequate surface prep.

Solution: If the blisters go down to the surface, try to remove the source of moisture. If they don't go all the way down, remove the blisters by scraping, then sanding; prime any bare wood and repaint.

Cracking and flaking. Splitting of dry paint film through at least one coat can lead to complete failure of the paint. Early on, the problem appears as hairline cracks; later, the paint flakes.

Possible cause: Over-thinning the paint, or spreading it too thin; painting when it's too cold or too warm, when the paint dries too quickly.

Solution: If the paint is adhering tightly to the surface, lightly feather the edges, prime and paint. If the cracking is all the way down to the surface, remove the paint. Old flaking paint may contain lead, so take appropriate precautions.

Question: "I have a concrete patio. I have painted it several times over the last few years with an epoxy paint. However, after a year or two the paint starts peeling and the patio must be repainted. I'm guessing that dampness from underneath the patio is causing the problem. Can you suggest a reasonably priced solution for refinishing the surface?

Answer: Staining your concrete patio is a better idea. Stain usually penetrates the surface, so it doesn't peel. Paint sits on the surface and is more prone to peel over time, especially in a humid, saltwater environment.

Q: "My parents live in a townhouse built in 1992 and have a slow-running bathroom-sink drain. Drain cleaner solves the problem for a while, but they were wondering if there are any preventive measures that can be taken. Someone suggested a vinegar solution, which seems more myth than maintenance.

A: The chief cause of slow-draining bathroom sinks is a combination of hair and soap, which congeals in greasy clumps, usually in the S trap. Plumber Marcel Paillard once suggested to me that the best way to keep gunk from building up is regularly using washing soda and water. Arm & Hammer Super Washing Soda is sold in supermarkets' laundry-detergent aisles.

A reader recently wrote about dust mites and baseboard heaters. Here's more information from Rutgers professor Joe Ponessa: "I hope your reader knows the front part of the baseboard enclosure can usually be removed for cleaning.

"Mites are killed by high temperatures (130 degrees F, according to the Centers for Disease Control, American Lung Association and many other sources) and dryness, so baseboard dust is an unlikely environment for them. Mites subsist on skin flakes, so bedding is their ideal environment. Control is attained by using allergen-impervious encasements for mattresses & pillows, and laundering bedding in hot water. (Same sources).

"Carpet is the next most likely place to find dust mites. Regular vacuuming, as you suggested, is a primary control measure. Not all HEPA vacs are created equal, however. A recent study in Consumer Reports showed that a mid-priced Kenmore vac outperformed some units costing twice as much."