InspectAPedia ^®

Paint Sample Chemical Analysis Procedures InspectAPedia®  -     A simple chemical analysis of chips of paint can often identify the type of paint used on a surface Identification of type of paint can detect incompatible paints and causes of paint failure on buildings Detailed procedures for preparing paint failure samples for lab analysis Guide to high power light microscopic examination of paint chips and fragments Simple chemical tests to aid in identifying acrylic/latex or oil/alkyd classes of paint Lab observations aid in diagnosing the cause of paint failure on surfaces

This article describes a simple procedure for preparing paint samples for reflected light low to high magnification microscopic examination in the paint failure laboratory. A procedure is described for mounting sectioned paint chips on edge for microscopic examination. This procedure is useful in the determination of paint layers, paint layer thickness measurement, and paint layer interactions. The procedure also permits detection of mold or debris which has been painted over.

Two simple chemical tests are described for identification of paint as acrylic or alkyd, useful as a quick, inexpensive alternative to pyrolosis gas chromatography, We include photographs of the procedure for preparing paint chips for cross-section and flat surface analysis. and photos of the results of simple chemical analysis to identify paint samples as acrylic or alkyd paints.

This document is a chapter of Diagnosing and Preventing Paint Failure on Building Exteriors. Readers should also see Paint Failure Case Photographs-SITE and then Paint Failure Case Photographs-LAB and see PAINT & STAIN GUIDE, EXTERIOR for a guide to the selection and proper application of paints and stains on exterior wood surfaces.The diagnosis and cure of paint failure on buildings, particularly on wood siding and trim, is quite possible if there is a careful and thorough inspection of the building, its history, its surfaces, and the actual points of paint failure. It is diagnostic to compare the same coating on the same type of surface at different locations on a building and in areas of failed and not-failed paint.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

Simple Chemical Tests Can Often Identify Acrylic and Alkyd Paints

The identification of a paint chip sample as acrylic or alkyd-based is important for art conservationists, but also for more prosaic paint failure investigators who examine buildings.

During investigation of peeling and flaking paint on a costly historic restoration project of an 18th century building we suspected that a contractor had been supplied incompatible paints or that not all of the primer used on the building was the same material, and that the primer was not intended for exterior use.

By identifying the type of paint used we made a definite and easy determination that the paint applied was not the paint for which the park service had contracted.

With as stance from two experts, one an experienced paint chemist and the other, an expert art conservator, we here document the procedure for two very simple chemical tests that can often (not always) distinguish between oil/alkyd paints and latex-based paints.

Paint testing laboratories use either chemical methods and/or infra-red spectrometry to identify binders used in paints. Infrared spectroscopy is the most fundamental way to identify almost any organic material.

Pyrolosis GC/MSD is a useful back up method, and has been used in the art conservation field. See Analysis of Modern Paints at References below.

All organic materials have a unique infrared spectrum or 'finger print'. Some paint testing labs (Bodycote) inform us that the following combination of paint testing methods are the most precise in paint identification and can be used to reverse-engineer a paint from a paint sample.

• Fourier transform infrared spectroscopy (FTIR) to determine the type of resin in the paint
• Thermogravimetric analysis (TA) to determine the fillers present in the paint
• Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy to determine the elemental composition of the paint chip.

These tests are costly, ranging from $450. to $1000. per test per sample. In contrast, the chemical tests we describe here should cost less than ten percent of those higher fees. However the tests need to be performed by an experienced forensic investigator or microscopist trained in microchemistry.

A Description of Two Simple Chemical Tests to Examine Paint Chips

Chemical tests to examine paint chips or painted surfaces, while less precise and less informative, are very quick, inexpensive, and can be used in the field as well as in the laboratory. Therefore chemicals are mainly used on site and infra-red is used in the lab.

The most common chemical methods for examining paint in the field or for a "quick lab test" are:

1. NaOH-solution will make alkyd and oil paint surfaces turn yellow, but will not affect acrylates. (4% NaOH, but KOH can also be used. KOH was used for the tests shown in photographs in this document.)
2. Ethanol will soften acrylates but will not affect alkyd and oil paints.

Mixed-base paints lead to ambiguous results: This chemical method for paint testing will not always give a definitive answer. For example if a water-based paint is comprised of both alkyd and acrylate components the chemical test will be ambiguous.

However these tests can be unambiguous: if the surface either turns yellow with NaOH or softens with ethanol, and if the converse test of the same sample using the opposite chemical does not produce the key reaction, then the test is reliable.

We performed the tests shown in this document, followed by sending samples of the same paints to an independent paint testing laboratory for advanced testing. The results of this advanced laboratory analysis will also be reported here as a cross-check on our chemical test for acrylic and alkyd paint.

Ethanol Test on Paint Chips Separate Acrylic from Alkyd

Here are photographs showing the effectiveness of the Ethanol test on two paint chips. One paint chip remained brittle and fragile as it was at the outset, unaffected by the ethanol, indicating that the chip was not an Acrylic. We suspected it was an alkyd paint, confirmed by the KOH test.

The second paint chip becomes soft after about 4 minutes in Ethanol, as we demonstrate by curling and rolling the previously fragile brittle chip using our forceps. This confirms that the ethanol-softened paint was an acrylic.

Paint chip remains flat = alkyd/oil: This paint chip remained flat and brittle, unaffected by submersion in ethanol, suggesting that it is not an acrylic paint. (We suspected that it was an alkyd or "oil" based paint).

Paint chip softens, curls = acrylic or latex: This paint chip curled when soaked in ethanol for four minutes, and was easily bent and rolled using our fine forceps as shown in the photo. This is an acrylic paint.

NaOH or KOH Test on Paint Chips to Separate Acrylic, Latex, from Alkyd

Here are photographs showing the effectiveness of the KOH test on two paint chip samples. One turned yellow (indicating Alkyd paint) and the other was unchanged (indicating not alkyd paint, in this case suspected Acrylic). [Photos coming]

Summarizing these tests: We use either chemical methods and/or infra-red spectrometry to identify binders. Chemicals are mainly used on site and infra-red is used in the lab. The most common chemical methods are:

1. NaOH-solution will make alkyd and oil paint surfaces turn yellow, but will not affect acrylates.
2. Ethanol will soften acrylates but will not affect alkyd and oil paints.

This chemical method is very crude and will not always give a definite answer (for example if a water-based paint comprises of both alkyd and acrylate components), but if the surface either turns yellow with NaOH or softens with ethanol, then you are in business!

Share this Article      

...

Technical Reviewers & References

Search InspectAPedia

• Daniel Friedman - principal author/editor of the InspectAPedia^® Website
• InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also include a list of recommended books for the specific article topic as well as other references, and information sources.
• Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
• Additional technical contributors & reference sources for this article are listed below.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

PAINT & STAIN GUIDE, EXTERIOR
PAINT FALURE, DIAGNOSIS, CURE, PREVENTION
PAINT FAILURE CHECKLIST
  EXTERIOR CLUES
  INTERIOR CLUES
  SITE HISTORY
  PAINT FAILURE INDICATORS
COMMON PAINTING MISTAKES
  BAD SURFACE PREP
  PAINTING SHORTCUT ERRORS
  PAINT OVER MOISTURE
  INCOMPATIBLE PAINTS
  PAINT in SUN or WIND
  PAINT on STUCCCO, FAILURES
PAINT FAILURE DICTIONARY
PAINT FAILURE ANALYSIS LAB PHOTOS
PAINT LAB SAMPLE PREPARATION
  Flat Surface View of Failing Paint
  Sectional View of Failing Paint
  Chemical Tests of Failing Paint
  Contributors & References

PAINT REFERENCES

• Leila Kotama, Product Manager, Tikkurila Paints Oy, Finland. Dr. Kotama has more than 20 years experience as a paint chemist.
• Ulrik Runeberg, Conservador , Museo de Arte Contemporaneo de Puerto Rico, San Juan Puerto Rico
• Bodycote Materials Testing, Ontario, Canada


• Paint and Surface Coatings, Theory and Practice, R. Lambourne & T.A. Strivens, Ed., Woodhead Publishing Ltd., William Andrew Publishing, 1999 ISBN 1-85573-348 X & 1-884207-73-1 [This is perhaps the leading reference on modern paints and coatings, but is a difficult text to obtain, and is a bit short on field investigation methods - DF]
• Analysis of Modern Paints, Thomas J.S. Learner, Research in Conservation, 2004 ISBN 0-89236-779-2 [Chemistry of modern paints, overview of analytical methods, pyrolysis-gas chromatography signatures of basic modern paints and their constituents, Fourier transform infrared spectroscopy for paint analysis, direct temperature-resolved mas spectrometry, and analysis in practice - technical reference useful for forensic paint science, focused on art works -DF]
• Seeing Through Paintings, Physical Examination in Art Historical Studies, Andrea Kirsh, Rustin S. Levenson, Materials in Fine Arts, 2000 ISBN 99-051835 [ forensic science, technical reference, focused on art works - DF]
• Paint Handbook: testing, selection, application, troubleshooting, surface preparation, etc., Guy E. Weismantel, Ed., McGraw Hill Book Company, 1981 [Excellent but a bit obsolete paint theory and practice, also a bit light on field investigation methods, out of print, available used-DF]
• Art, Biology, and Conservation: Biodeterioration in Works of Art, Robert J. Koestler et als. Eds., Metropolitan Museum of Art, 2003, ISBN 1-58839-107-8
• Paint Test Laboratory Listings Welcome: independent forensic and microscopic or chemistry labs offering paint analysis or paint failure services are welcome to be listed here at no fee. See our ADVERTISING & LINK EXCHANGE POLICY and Contact Us

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• ...

More Information on Building Diagnostic Inspections and Repairs

• Exteriors, Landscaping, & Siding - Inspection, Repairs, Product Failures

• Quotes in the opening text of this document are from the encyclopedic but not quite complete paint website: PPG Exterior Failures http://www.ppg.com/getpaint/etraining/solver/exterior.html

InspectAPedia® Home & Site Map - Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice: In-depth research & advice on diagnosing, testing, correcting, & preventing building defects & indoor environmental hazards. Unbiased information, no conflicts of interest.

The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems

Use this simple, economical mold test kit by following our instructions on how to collect and mail mold samples to our lab

Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.

Building Inspection, Problem Diagnosis, Forensic Investigation & Testing, Repair Consulting

Contact Daniel Friedman for website content suggestions or for fee-paid consulting