Q. I invested in some quality paint and varnish brushes. I got careless and didn't clean them properly. Now the bristles are as hard as a rock. Paint thinner at this point doesn't have any effect. Can these brushes be saved?

A. Quality brushes, even those that appear to be petrified, can often be revived. It's worth a try. You will need to purchase a commercial brush cleaner to do the job.

There are two types available, solvent-based and water-based. I prefer the solvent-based product, which is good for any brush (having natural or synthetic bristles) and a must for brushes saturated in oil-based paint or varnish. The water-based product is good only for synthetic brushes. Both cleaning products work to dissolve the hardened paint in the bristles.

Brushes must soak in the cleaning solution overnight, and in some cases even longer, to give the solution ample time to work. Use a jar or coffee can large enough to suspend the brush. Use wire or a clamp to secure the handle in the proper position. If the bristles are allowed to rest on the bottom of the container, you will end up with a bent, out-of-shape brush. With the solvent-based solution, it is wise to cover the top of the container with foil or plastic wrap to prevent evaporation.

Once the bristles become pliable, remove the brush from the container. Use a brush comb to remove any solids still clinging to the bristles. If using a solvent-based cleaner, soak the brush in a clean solution of the product for several hours to remove any residual paint that may still cling to the bristles. You can skip this step if using a water-based product.

The final cleaning step with either solution is to wash the brush in a solution of dish detergent and warm water to remove all of the cleaning solution. Rinse thoroughly with clear water and squeeze as much of the moisture out of the bristles as possible, keeping them flat and uniform. Let the brush air-dry.

When storing brushes, wrap the bristles in plastic or a paper towel, secured with a rubber band. You want to maintain the original flat shape of the brush. It's best to hang brushes from the holes in their handles during storage.

Several months after repainting our master bathroom, the paint is blistering and lifting. We also have signs of mildew. What should we do to remedy the problem prior to repainting?

Bubbles resulting from localized loss of adhesion and lifting of the paint film from the underlying surface are usually caused by a moisture problem, which is also the source of your mildew problem. Applying oil-based or alkyd paint over a damp or wet surface will cause the blistering, as will exposure of latex paint film to high humidity or moisture shortly after a fresh coat of paint has been applied (even though it seems dry). The problem is more likely if there was inadequate surface preparation before applying the paint.

Moisture problems are prevalent in bathrooms and kitchens. They can also be a problem in other rooms when moisture seeps into the house through exterior walls (which is less likely with latex paints). If the paint blisters do not go all the way down to the substrate, remove blisters by scraping and sanding, and repaint with a quality acrylic latex interior paint. If blisters go down to the substrate, remove the source of the moisture, if possible. Repair loose caulking; consider installing vents or exhaust fans. Remove blisters as above, remembering to prime before applying the top coat.

Mildew is also caused by moisture conditions. Bathrooms, kitchens and laundry rooms are particularly susceptible. Black, gray or brown spots on the surface of paint or caulk should be tested by applying a few drops of household bleach to the discoloration. If discoloration is bleached away, it is most likely mildew.

Mildew often forms on a surface that tends to be damp or receives little or no direct sunlight. Failure to prime a bare wood surface before applying paint makes the surface more susceptible to mildew growth. Painting over a substrate or coating on which mildew has not been properly removed just promotes continuation of the problem. All mildew must be removed from the surface by scrubbing with a diluted household bleach solution (one part bleach, three parts water), while wearing rubber gloves and eye protection. Rinse thoroughly with clear water.

Take precautions to prevent the return of mildew growth by removing the source of moisture as recommended above. Repaint the area with a quality latex paint, adding a mildew killer if possible. There is a special mildew-proof paint on the market--Perma-White, marketed by William Zinsser & Co. It is available nationwide, or you can contact the manufacturer directly for an outlet in your area (173 Belmont Dr., Somerset, N.J. 08875).

This product, which carries a five-year mildew-proof guarantee, is moisture-resistant as well as blister-proof and self-priming. It comes in both satin finish and high-gloss.

For more information on paint problems and solutions, consumers can contact the Rohm and Haas Paint Quality Institute, which provides consumer information. It's purely an educational institution and does not endorse specific brands. Contact the institute through its World Wide Web site (www.paintquality.com).

Last year, we painted the stucco exterior of our home. Within this short period it has begun to peel and flake in sections. One of our neighbors insists that we should never have painted stucco. However, we have painted stucco in a previous home with no problems. Do you know what might have caused the peeling and what we can do now to correct the problem?

Paint on stucco can fail for several reasons, including poor preparation of the surface or too much moisture or alkalinity in the stucco. Climatic conditions are another major factor. In warmer climates where the temperature does not drop below freezing, the paint coating is not subject to freeze-thaw conditions, which cause problems. In colder climates, moisture migration through walls that have no vapor barriers often causes paint to fail.

The most durable refinishing for stucco would be a cement-base stucco coating; this should be the finish of choice in colder climates. These are available in dry form and must be mixed with water. Mix the stucco according to directions and apply over the old stucco using a rental hopper-type sprayer or a sponge, brush or roller. There are several manufacturers of stucco resurfacing products, which come in a wide choice of colors.

Professional resurfacing is also available in most areas. If you use a professional, get several bids and read all warranties carefully. Some firms will guarantee their work for up to 20 years.

If you live in a moderate climate, not subject to the freeze-thaw cycle, you can consider using paint on stucco. Check with a qualified paint dealer in your area for help in choosing a good masonry paint and the right application techniques. Usually a paint roller with a denser, longer nap is best for application on the rough stucco texture.

Regardless of the resurfacing method you choose, the existing surface must be cleaned thoroughly to remove all loose material. Brushing with a stiff bristle brush may be adequate, but power-washing equipment can be rented. Sometimes even sandblasting is necessary. After cleaning, rinse the surface and let it dry.

A new stucco coating is more durable than paint. Painting is less expensive but a viable option only in moderate climates. Even then, repainting will be required periodically.

Write to Here's How, Copley News Service, P.O. Box 120190, San Diego, Calif. 92112-0190, or e-mail copleysd@copleynews.com. Only questions of general interest can be answered.