Archive for the ‘Exterior Painting’ Category

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.

What is Blistering ?

Bubbles resulting from localized loss of adhesion and lifting of the paint film from the underlying surface.

Possible Cause:

• Painting a warm surface in direct sunlight.
• Application of an oil-based or alkyd paint over a damp or wet surface.
• Moisture escaping through the exterior wall (less likely with latex paint than with oil-based or alkyd paint).
• Exposure or latex paint film to dew, high humidity or rain shortly after paint has dried, especially if there was inadequate surface preparation.

Solution:

• If blisters go down to the substrate, try to remove the source of moisture. Repair loose caulking; consider installing an exhaust fan. Remove blisters.
• If blisters do not go all the way down to the substrate, remove them by scraping, then sanding; prime any bare wood and repaint with a quality exterior paint.

What is Poor Galvanized Metal Adhesion?

Paint that has lost its adhesion to a galvanized metal substrate.

Possible Cause:

• Improper surface preparation, such as inadequate rust removal.
• Failure to apply a primer before application of an oil-based or vinyl latex paint.
• Failure to sand baked-on enamel finishes or glossy surfaces before painting. 

Solution:

Any rust on the metal should be removed with a wire brush; then, an acrylic latex corrosion-resistant primer should be applied (one coat is usually sufficient). New or previously painted galvanized metal that is completely rust-free can be painted with a top quality acrylic latex paint without applying a primer; however, a metal primer should always be applied to unpainted galvanized metal before applying an oil-based or vinyl latex top coat.

Source: Paint Quality Institute

What is Alligatoring?

Alligatoring is patterned cracking in the surface of the paint film resembling the regular scales of an alligator. 

Possible Cause:

• Application of an extremely hard, rigid coating, like an alkyd enamel, over a more flexible coating, like a latex primer.
• Application of a top coat before the undercoat is dry.
• Natural aging of oil-based paints as temperatures fluctuate. The constant expansion and contraction results in a loss of paint elasticity.

Solution: 

Old paint should be completely removed by scraping and sanding the surface; a heat gun can be used to speed work on large surfaces, but take care to avoid igniting paint or substrate. The surface should be primed with a high quality latex or oil-based primer, then painted with a top quality exterior latex paint.

Source: Paint Quality Institute