Using the wrong paint - the role of incompatible paints in building paint job failure.

Here we explain how and why using incompatible types of paint in successive coatings can lead to paint failure on a building interior or exterior surface.

INCOMPATIBLE PAINTS - Improper, Incompatible Paint Selection - Bad Chemistry

Our photo shows an exterior paint failure that occurred when a mix up led to both interior paints and defective paint product used on a building exterior. The white primer was intact.

The color coat began peeling even during the paint job, that is well before painting the building had even been completed.

This paint was extremely- thin - both to the naked eye and by measurement: we measured it at numerous building locations on all sides and in all failing areas, so on-site we suspected that the paint may have been over-thinned, perhaps on-the job by the painter (who denied thinning the paint) or by the manufacturer as a production or other error (who also denied any such error).

But for a certain conclusion of the cause of this paint failure, expert laboratory analysis was needed as well.

Paint failures can occur, such as failure of a paint to bond with a surface, failure of inter-coat bonding, or even dissolving of one paint coat by another, if incompatible paints are applied to a surface.

For example, surfactant leaching can occur if there is an incompatibility between the primer coat and the finish coat.

Paint chemists formulate primers and topcoats to work together as a tested and proven paint coating system.

See deails in our Paint Failure Dictionary at DEFINITION of SURFACTANT LEACHING

[Click to enlarge any image]

• Painting a new coating on incompatible already-coated surfaces, including the paints or paint solvents: - applying a coating which is chemically incompatible with the existing layers. (Usually see wrinkling, staining, blistering, loss of adhesion, usually occurring while the new coating is still wet.)
  
  See DEFINITION of INCOMPATIBLE PAINTS / SURFACES in our Paint Failure Dictionary
  
  See DEFINITION of PAINT ADHESION FAILURE in our Paint Failure Dictionary
• Applying paint where a stain or pigmented stain is more suitable, or without first applying the proper primer over a stained surface
• Using an indoor paint outside
• Omitting the first-coat primer or conditioner recommended by the top coat paint manufacturer
• Using a primer as a top-coat
• Contaminating varnish, shellac, or lacquer with moisture/water

WRONG PAINTS - Improper Paint Type Selection

There are lots of examples of using the wrong paint (besides the incompatible paints discussed above.

• Using an interior paint outdoors
• Using a paint which lacks the necessary attributes for a specific application - painting a wood siding paint on a metal water storage tank
• Painting an oil top coat over previous acrylic/latex top coats
• Using a defective paint which has been improperly formulated at the factory
• Using a defective paint product that has been modified in the field, such as by over-thinning
• Failure to use the manufacturer's recommended primer, particularly on challenging surfaces such as new stucco, can lead to early paint failures.
  
  See PAINT on STUCCO, FAILURES for details.

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

Comment: painting company defends the failure of its paint job

(June 8, 2011) Amy said:

The picture used in this example of a paint failure has not been permitted. It also states that the color paint began to peel during the paint job-this is incorrect. The person painting this job noted that the "color" coat did not seem to be curing as he was able to scratch the "color" coat.

Two paint anaylsis(es) were performed by two separate labs, which concluded two completely different opinions, one analysis concluded that the "color" coat was applied too thick and the other stated that the "color" coat was applied too thin.

The team that worked on this job followed the instructions given to them by both the paint company where the paint was purchased and also by reading the paint can/s.

Reply:

Thanks for the comment, Amy.

We are dedicated to making our information as accurate, complete, useful, and unbiased as possible: we very much welcome critique, questions, or content suggestions for our web articles.

When we inspected the site & collected and tested paint samples from this project paint was peeling badly on most building surfaces, even under a porch roof.

There was indeed an adhesion problem and in un-peeled areas it was possible to scratch loose the color coat. But that condition had badly deteriorated to free peeling as shown in our photo.

At first look we thought that perhaps the paint was improperly thinned but both the job history and lab tests argued against a problem with paint solvents.

A conclusion the paint was too thin was easily supported by comparing the measured thickness of the color layer with the paint specification, but that did not appear to be the central issue.

An earlier lab reporting that paint was too thick could not possibly have measured the same paint samples correctly.

The second lab included complete photo ducmentation of the actual measurement, scale, and microscope calibration.

The "too thick" lab scraped samples from several building surfaces and shoved all of them into the same baggie, making accurate diagnosis and comparison of the better performing paint areas and badly peeling areas impossible.

Amy if you read the topic headers above you will see that you don't need to defend [your] painters who did the work at this job.

Tests on the paint in the forensic lab and done in consult with paint manufacturer chemists suggested that the paint failure should not be laid at the doorstep of the painting company if it appeared to originate with the paint or paint supplier.

In fact it appeared that the paint sold for the job was not the paint that was delivered and applied - there appeared to be a labeling and shipping error.

The photo shown above is our own, taken on site during an independent paint failure investigation; your comment about the photo permission is thus not pertinent.

See PAINT FAILURE CASE PHOTOS, LAB

This 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.

...

Continue reading at PAINT on STUCCO, FAILURE or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• GRAFFITI REMOVAL FROM BRICK CONCRETE STONE SURFACES
• PAINT & STAIN GUIDE, EXTERIOR for a guide to the selection and proper application of paints and stains on exterior wood surfaces.
• PAINT FAILURE CASE PHOTOS, SITE
• PAINT FAILURE CASE PHOTOS, LAB
• PAINT FAILURE, DIAGNOSIS, CURE, PREVENTION - home
• PAINT FAILURE DICTIONARY - illustrated list of all types of paint failures
• PAINTING MISTAKES
  • BAD SURFACE PREP
  • INCOMPATIBLE PAINTS
  • PAINT on STUCCO, FAILURE
  • PAINTING SHORTCUT ERRORS
  • PAINTING OVER MOISTURE
  • PAINTING in SUN or WIND

Suggested citation for this web page

INCOMPATIBLE PAINTS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to PAINTS & STAINS & FAILURES

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