Paint Problems

Listed below are examples of common paint problems and their characteristics with a full description and recommended solutions.  Courtesy of Sherwinn-Williams Company.

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Cause: Frosting is the formation of white surface crystals on paint surfaces. When present, these crystals are most noticeable on dark colors and form in areas that are protected from the cleansing action of rainfall. The crystals form when the paint is exposed to excessive moisture (dew, condensation, rain, etc.) or cool temperatures during the curing process and create a surface condition called "frosting."

Solution: Apply paint to all surfaces during climatic conditions that allow proper curing of the paint film. If frosting occurs use a garden hose to flush crystal formations with warm tap water. Water-soluble crystals will disappear. Follow-up water flushing may be required at later dates and eventually crystal formation will cease. If crystals are not water-soluble, then other actions are required. Allow surface to dry thoroughly. Using medium grit sanding paper, lightly sand crystals away until original color of paint film reappears. Remove all loose dust and apply a uniform coat of A-100 Alkyd Wood Primer. This alkyd undercoater will act as a barrier coat preventing the formation of future frosting. Apply latex or alkyd topcoat.

Note: Frosting may dissipate over time (several weeks or months)

Caution: Wear a face mask to avoid inhalation of dust particles during the sanding procedure.

Recommendations: One "barrier" coat of A-100 Alkyd Wood Primer

One or two coats Exterior Latex House and Trim Paint

Cause: The appearance of mildew depends on various conditions, which are:

Continuously high humidity. As the humidity increases, mildew growth becomes more rapid.

High average temperature. Optimum temperature for mildew growth is 77 degrees F.

Poor ventilation. Still air increases mildew growth.

Composition of surface. Mildew will grow on any surface that provides a nutrient, even dirt.

Light colors of paint film. Colors that do not absorb the sun's heat provide a surface for mildew growth. Dark colors become hot and discourage mildew growth.

Solution: Wash mildewed areas with a solution of one part household bleach and three parts water.* This will destroy mildew and bleach stains caused by mildew growth. Apply solution by brush or a garden sprayer apparatus. Heavy mildew may require additional applications, and scrubbing may be required. Flush area with clean water to remove bleach solution. Allow to dry thoroughly.

*Follow label cautions when using bleach solution.

Recommendations: Spot prime bare areas

Two coats Exterior Latex House and Trim Paint

Note: If mildew growth is excessively heavy, add additional mildewcide to paint for added protection.

Cause: Peeling is caused by poor surface preparation, and refers to the removal of strips or sheets of paint due to loss of adhesion. The loss of adhesion could be the result of: painting over a coating containing wax; an excess buildup of moisture within the wood; painting over an old, smooth coating; or painting over heavy chalk surfaces.

Other surface conditions or contaminants known to affect the adhesion of newly applied topcoats are oil, grease, various forms of pollution such as dust, dirt and mildew, applying paint over hard glossy surfaces and excessively thick film topcoats.

Peeling may also be the result of applying latex paint below its recommended application temperature.

Solution: Proper surface preparation will prevent peeling of the topcoat. If a peeling situation persists, the loose paint must be completely removed. Prepare surface by removing or abrading the problem surface. Sand all bare wood to fresh wood.

Remove surface contaminants with naphtha solvent, detergents and water. Glossy surfaces must be scuff sanded. All surfaces must be rinsed with clean water and allowed to dry thoroughly. Exposed wood areas must be sanded to fresh wood and primed with an alkyd or latex primer.

Caution: Wear a face mask to prevent inhalation of dust particles during the sanding procedure.

Recommendations: One coat A-100 Exterior Wood Primer

Two coats Exterior Latex House and Trim Paint

Note: When painting between 35 degrees F and 50 degrees F or when the temperature is expected to drop to between 35 degrees F and 50 degrees F within 48 hours of painting, apply two coats of LowTemp 35 Acrylic Latex House Paint after priming with one coat A-100 Exterior Wood Primer.

Cause: As a rule, paints do not adhere well to smooth metal surfaces. Galvanized metal, a product used to make corrugated sheets, gutters and downspouts, is not only smooth, but the metal is coated with a thin to heavy layer of oil to prevent white rust.

When oily galvanized steel is painted during cold and highly humid conditions, the curing of the paint film is retarded, resulting in wrinkling and loss of adhesion (see insert).

Alkyd paints that are applied to galvanized metal will produce an acceptable paint film initially, but will quickly fail. The zinc of the galvanize will chemically react with the alkyd binder of the paint, which leads to extreme paint peeling.

When galvanized metal is allowed to remain exposed to the atmosphere, the protective zinc metal coating will oxidize into a white rust until eventually the zinc metal is depleted. The underlying steel will then rust to the offensive red color.

Solution: The protective layer of oil must be completely removed. Solvent wiping using a water soluble cleaning agent or VM&P naphtha is recommended for small manageable areas. Many solvents, including mineral spirits, leave a thin layer of residue which leads to adhesion failure of the paint film.

Weathered galvanize develops a layer of "white rust" which must be removed to ensure good adhesion of the applied paint. Wire brushing is recommended.

Iron rust must be removed by wire brushing followed by sanding with a productive grit sandpaper. Severely rusted gutters should be replaced.

Caution: When removing "white rust", wear a face mask to avoid inhalation of dust particles.

Recommendations: Galvanized (New)

Two coats Exterior Latex House and Trim Paint

Galvanized (weathered)

Two coats Exterior Latex House and Trim Paint

Galvanized (red rust)

One coat DTM Primer/Finish

Two coats Exterior Latex House and Trim Paint

Proper surface preparation will prevent peeling of the topcoat. If a peeling situation persists, the loose paint must be completely removed. Prepare surface by removing or abrading the problem surface. Sand all bare wood to fresh wood.

Remove surface contaminants with naphtha solvent, detergents and water. Glossy surfaces must be scuff sanded. All surfaces must be rinsed with clean water and allowed to dry thoroughly. Exposed wood areas must be sanded to fresh wood and primed with an alkyd or latex primer.

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