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Photo of paint solvent blistering (C) Daniel Friedman Painting in Sun or Wind as a Cause of Paint Failure

  • PAINTING in SUN or WIND - CONTENTS: Photo-guide to paint failures caused by sun or wind: thermal blistering or "temperature blisters". Heat and too-rapid drying of paints caused by sun or wind can lead to blisters, craters, and eventual pits, peeling, and paint failures. How to diagnose wind or sun exposure during paint application as the cause of failing paint on a building exterior or interior. How does wind exposure or too much sun exposure during painting cause the paint to later fail?
  • POST a QUESTION or READ FAQs about the effects of sun or wind exposure on paint job success and failure.
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Causes of paint job failures: painting in direct sun or in windy conditions:

Here we explain how and why painting a building exterior in hot sun or when there is a strong wind can lead to early paint failure, blisters, and other paint problems. Heat and too-rapid drying of paints caused by sun or wind can lead to blisters, craters, and eventual pits, peeling, and paint failures.



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PAINTING IN SUN - Some Paints Fail If Applied in Direct Hot Sunlight

Photo of paint solvent blistering

[Click to enlarge any image]

Painting in sun and also painting over a primer or base coat that has not adequately dried can cause solvent blisters that are hard to see with the naked eye but are easily identified by microscopic examination.

Thermal blistering, or "temperature blistering" occurs when painting in sun, or if paint is applied to hot surfaces; the blister may be from moisture or solvents in the paint itself.

Paint Solvent blisters are small, usually microscopic - you won't see them by naked eye.

Both thermal blistering and solvent blistering may occur on the same surface.

See PAINT FAILURE DICTIONARY we discuss the details of these paint failure mechanisms. Our photos, below, show solvent blistering and cratering.

Photo of paint solvent blistering

[Click to enlarge any image]

Depending on the chemistry and intended application of a particular paint, if applied to a too-hot surface (perhaps over 80 degF) the paint may form a skin which retards evaporation of the remaining carrier vehicle or solvent in the underlying paint.

A possible result is the formation of paint blisters, some of which may rupture to form pinholes in the coating surface.

A second possible result of painting on a too-hot surface is the formation of cracks in the painted surface where blisters have lifted and thinned the paint coating.

Blister cracks, like other cracks in a paint film, invite moisture penetration and later separation of the paint from the coated surface. Moisture behind the paint layer leads to early paint failure. Lots of experts know that.

But an accurate diagnosis of the precise paint failure mechanism distinguishes between building interior moisture, building leaks, and an external failure of the paint coating due to having been applied in hot sun or over a too-wet primer coat.

PAINTING IN WIND - Some Paints Fail if Applied in Windy Conditions

Depending on the chemistry and intended application of a particular paint, if applied in windy conditions, the paint may form a skim coat too rapidly, retarding evaporation and leading to cracking or blistering failure as just described above for the "painting in sun" case.

Be sure to follow the recommendations of your paint supplier and paint manufacturer in choosing the right paint for the proper application.

Painting in sun or wind can be a particular problem when painting new stucco surfaces.

See PAINT on STUCCO, FAILURES for details.

This building paint failure article series reviews common building exterior & interior painting mistakes, describes how to diagnose paint failures on buildings, and outlines a procedure for diagnostic field inspection & lab testing of failed painted surfaces. We include photographs of paint failures on buildings and more photos of forensic paint laboratory examination of samples of failed paint useful to assist in diagnosing the probable cause of each type of paint failure.

Roof Paint Manufacturer's Painting Instructions about Temperature, Sun, Wind, Moisture, Rain

Question: Do both sunny and windy conditions affect roof compound paint as well?

26 Sept 2015 max said:

Very good article thank you. Do both sunny and windy conditions affect roof compound paint as well? Or do these cracks appear more in "normal" types of paint. As painting in the shade is hard for me I need to do it in the sun. What temperature do you think can cause issues? I guess when it´s sunny but not hot it would be ok to paint?

Reply:

Yes certainly the results from painting any surface can be affected by sun, wind, moisture, rain, though I have no objective data for roofs.

I think that the type of paint as well as surface conditions would be the determining factors. A paint with very volatile solvents, a paint that skins over quickly when exposed to sun, wind, heat, a paint (such as latex) that will permit some moisture to pass out, are examples of factors involved.

You need to see what is specified by the manufacturer of the particular paint you're applying.

Aluminum Roof Paint Application

Gardner-Gibson, a manufacturer of alulminum roof coating paint specifies these details for using their roof coating on metal, modified bitumen, rolled roofing, built up roofing (BUR), or on an existing aluminum coated roof:

The roof surface must also be clean of loose debris, dry, and if necessary patched over cracks, bliseters or other damage.

Similarly, Graco, a producer of roof coatings, describing application of their GracoRoof® coating that can be used on many types of roof surfaces as well as on RVs and campers and mobile homes, (but not asphalt shingles) advises:

Do not apply in temperatures below freezing, above 120°F (49°C) or if rain is expected within 2 hours.

- Retrieved 26 Sept 2015 original source: http://www.gacoretail.com/gacoroofinstructions.html

White Elastomeric Roof Coating Application: acrylic latex roof paint

New York State provides the following guidance that was in turn developed by Henry Company, a California firm at www.henry.com, for a water-based acrylic-latex roof coating. This paint may also be applied to mineral surface cap sheets (conventional, SBS, APP), smooth surface BUR, SBS, APP (with a base coat of asphalt emulsion first), metal roofs (also with a base coat of asphalt emulstion), stucco parapet walls, masonry parapet walls, aged PVC, EPDM, Hypalon roof membranes, and also as a re-coate of polyurethane foam roofs.

This coating is not recommended over walking decks, over gravel, T.P.O., shingles of any kind, or old roofs that are too dry and brittle to withstand the shrinkage stresses that occur after the application of any coating.

- retrieved 26 Sept 2015 original source http://www.nyc.gov/html/coolroofs/downloads/pdf/HE280DC_techdata.pdf

Painting Mistakes Articles

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Continue reading at PAINT FAILURE LAB PHOTOS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see PAINT FAILURE CASE PHOTOS, SITE and also PAINT FAILURE CASE PHOTOS, LAB

Or see PAINT FALURE, DIAGNOSIS, CURE, PREVENTION - home

Or see PAINT & STAIN GUIDE, EXTERIOR for a guide to the selection and proper application of paints and stains on exterior wood surfaces.

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