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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 Questions & answers about paint testing methods, forensic microscopy and microchemistry for paint type identification

Paint sample or chip tests for paint type identification: oil/alkyd vs. latex/acrylic. 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 article is part of our series: 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.

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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!

Frequently Asked Questions (FAQs) about paint failure forensic laboratory test procedures: chemical tests and microchemistry

Question: what technique can I use to distinguish between acrylic and oil-based varnishes?

I have a client who suspects that a [wood floor in a sports facility] was varnished with acrylic rather than oil based varnish. Can you advise me on techniques for confirming the identity of varnish scrapings. I generally use polarizing light microscopy for small particle id but would like to know your approach. Thank you. [Anon.]

Reply: these microchemical methods provide a quick simple forensic procedure that often is sufficient for paint base type identification

Anon: During some investigative work for the NPS a while back I contacted the chemists at several paint companies for help with defining an alternative method for paint characterization other than the very expensive (try more than $1000./sample) gas chromatography. Worse, not only was that method very costly but when I went to one of the biggest test outfits in North America, they did a horrible and incompetent job. It was evident that at least some of the most costly and sophisticated paint testing labs, their technicians, and procedures have a rather specific focus (such as auto body paint) that may not include expertise on paint analysis for building failures nor for works of art (my areas of interest).

Please take a look at the microchemistry alternative above at Chemical Tests of Failing Paint. There we distinguish between acrylic/latex and oil/alkyd using this method - I invite you to try it and to let me know how you make out or whether or not you have further questions.

Note that although your question referred to oil based varnish, there is virtually no true oil based paint currently sold (that is traditional linseed oil based paints) - they've all been replaced with alkyds. Therefore I think that's what your client wants to look for. If you know otherwise do let me know.

Incidentally, I considered trying to use PLM along with the Baekke method, our standard color chart, and a full set of refractive index liquids to try identifying paint materials. While that approach is rather good at the forensic identification of a very wide range of particles and fibers, without some help from a paint chemist and some specific information not at hand about the precise optical properties of alkyd paint chips and acrylic paint chips, I'm afraid we'd be wasting our time on that approach when making distinctions of chemical constituents.

Finally, when investigating questions about the possible use of a paint product that was not the one anticipated, in addition to forensic investigation of the paint and the building surfaces, it is often most useful to do some old-fashioned detective leg work: obtain copies of the invoices that document where the coating products were purchased as well as just what was bought. Sometimes too we can find leftover paint or coating and primer cans or containers and we also sometimes find in job site photographs an image of the paint cans and their labels.

Questions & Answers regarding this article

Questions & answers about paint testing methods, forensic microscopy and microchemistry for paint type identification.

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• 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]
  Provides a comprehensive reference source for all those in the paint industry, paint manufacturers and raw materials suppliers, undergraduate and postgraduate students, and industrial paint users. R. Lambourne was in the Research Department at ICI Paints Division and the Industrial Colloid Advisory Group, Birstol University, UK.
• 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. Contact Us

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

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
• 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 mass spectrometry, and analysis in practice - technical reference useful for forensic paint science, focused on art works -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
• Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF - ** Particularly useful text **
• Understanding Ventilation, John Bower, The Healthy House Institute, ISBN 0-9637156-5-8, 1995 [General building science-DF - ** Particularly useful text. Mr. Bower has retired from the field but his book continues to be important]
• Dampness in buildings, Diagnosis, Treatment, Instruments, T.A. Oxley & E.G. Gobert, ISBN 0-408-01463-6, Butterworths, 1983-1987 [General building science-DF]

• Carson Dunlop's Home Study Course for Home Inspectors can be examined online at that company's website. More about home inspector education and other educational materials is organized at InspectAPedia.com at Home Inspector Education.
• Certainteed Weatherboard fiber cement siding and trim products - see certainteed.com/ or see certainteed.com/resources/sidingandtrimspecsheet.pdf
• "Moisture Control in buildings: Putting Building Science in Green Building," Alex Wilson, Environmental Building News, Vol. 12. No. 5. [Good tutorial, "Moisture 101" outlining the physics of moisture movement in buildings and a good but incomplete list of general suggestions for moisture control - inadequate attention given to exterior conditions such as roof and surface drainage defects which are among the most-common sources of building moisture and water entry.--DJF]
• Masonite Woodruf® Roofing or Masonite OmniWood® Siding Lawsuit Settlement Notice - PDF file
• Paint Handbook: testing, selection, application, troubleshooting, surface preparation, etc., Guy E. Weismantel, Ed., McGraw Hill Book Company, 1981, ISBN-10: 0070690618, ISBN-13: 978-0070690615, [Excellent but a bit obsolete paint theory and practice, also a bit light on field investigation methods, out of print, available used-DF]
  How to select and apply the right paint or coating for any surface. The first major reference to help you choose the correct paint or other finish to do the job best on a particular surface exposed to a particular environment. Experts in the field give full advice on testing surface preparation, application, corrosion prevention, and troubleshooting. The handbook covers wood, metal, composites, and masonry, as well as marine applications and roof coatings. A ``must'' working tool for contractors, architects, engineers, specification writers, and paint dealers.
• 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]
  Provides a comprehensive reference source for all those in the paint industry, paint manufacturers and raw materials suppliers, undergraduate and postgraduate students, and industrial paint users. R. Lambourne was in the Research Department at ICI Paints Division and the Industrial Colloid Advisory Group, Birstol University, UK.
• 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]
• Sealants, Durability of Building Sealants (RILEM Proceedings), J.C. Beech, A.T. Wolf, Spon Press; illustrated edition (1995), ISBN-10: 0419210709, ISBN-13: 978-0419210702
  This book presents the papers given at the RILEM Seminar held at the Building Research Establishment, Garston, UK in October 1994. The book provides an opportunity for researchers to review up-to-date progress towards the achievement of the objectives of the standardisation of laboratory techniques of sealants in the variety of service conditions to which they are exposed.
• Soiling and Cleaning of Building Facades (RILEM Report), L.G.W. Verhoef (Editor), Routledge; 1 edition (November 3, 1988), ISBN-10: 0412306700, USBN-13: 978-0412306709
  The report of a comprehensive investigation by RILEM which examines all aspects of the cleaning of facades, subject to soiling by both biological and non-biological agencies. The contributors are international authorities working in this field giving essential advice to all those who need to know how to approach the problems connected with the soiling and cleaning of building facades.
• Staining, Prevention of Premature Staining in New buildings, Phil Parnham, Taylor & Francis; 1996, ISBN-10: 0419171304, ISBN-13: 978-0419171300
  The appearance of ugly staining early in a buildings life, ruins an otherwise pleasing appearance, tarnishes the image of the owners and gives rise to costly refurbishment works. In this book Phil Parnham raises a number of questions that should be considered whenever a new building is being designed or built. These are: * why has staining become so prominent; * what causes premature staining; which parts of new buildings are likely to be affected; * how can it be avoided? By using a number of highly illustrated case studies, the author answers these questions and ends by suggesting measures that should be taken by all design and construction professionals to prevent premature staining.
• "Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
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