Archive for February, 2010

What Is Mildew?

Black, gray or brown areas on the surface of paint or caulk.

Possible Cause:

• Forms most often on areas that tend to be damp, and receive little or no direct sunlight (walls with a northerly exposure and the underside of eaves are particularly vulnerable).
• Use of a lower quality paint, which may have an insufficient amount of mildewcide.
• Failure to prime bare wood before painting.
• Painting over a substrate or coating on which mildew has not been removed.

Solution:

Test for mildew by applying a few drops of household bleach to the discolored area; if it disappears, it is probably mildew. Remove all mildew from surface by scrubbing with a diluted household bleach solution (one part bleach, three parts water); wear rubber gloves and eye protection. Power washing is also an option. Rinse thoroughly, prime any bare wood then apply one or two coats of top quality exterior paint, which typically contains mildewcide.

What is Chalking?

Chalking is the formation of fine powder on the surface of the paint film during weathering, which can cause color fading. Although some degree of chalking is normal, desirable way for a paint film to wear, excessive film erosion can result in heavy chalking.

Possible Cause:

• Use of a low-grade, highly pigmented paint.
• Use of an interior paint for an outdoor application.

Solution:

First, remove as much of the chalk residual as possible, use a stiff bristle brush (or wire brush on masonry) and then rinse thoroughly with a garden house; or use power washing equipment. Check for any remaining chalk by running a hand over the surface after it dries If noticeable chalk is still present, apply a quality oil-based or acrylic latex primer (or comparable sealer for masonry), then repaint with a quality exterior coating; if little or no chalk remains and the old paint is sound, no priming is necessary.