Paint Sample Cross-Section Preparation and Analysis Procedures InspectAPedia® -
How to cut and prepare cross-section samples of failing paint for forensic analysis of the cause of paint failure on a building or on other painted surfaces including art work
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
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This article describes a simple procedure for preparing cross-section cut 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.
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.
How to Prepare a Cross-Sectional View of Failing Paint Chips for Paint Failure Diagnosis
In addition to the examination of the flat surfaces of paint chips under the microscope, the examination of edge-view sectioned paint chips can yield important information. Yet some analysts may be unfamiliar with simple
and quick procedures that permit examination of paint in this diagnostic view. It is this more unusual edge view
procedure which we want to document here.
We make use of a sample lamination procedure introduced by the McCrone
Research Institute, Chicago, IL. McCrone offers advanced courses in forensic microscopy useful across various disciplines.
(The author has no affiliation with McCrone but is a graduate of a number of McCrone's courses.)
The examination of the edge of a paint chip sample can provide
critical information such as:
The number of individual paint layers on the surface represented by the paint chip sample. The building history is visible in its paint layers, including paint thickness, paint colors, and in some cases even the weather conditions during the painting process are all visible in this forensic approach to paint investigation.
Precise measurements of each individual paint thickness layer, and, by examining along individual samples as well
as by examining multiple paint samples, the variation in paint thickness per layer can also be estimated.
Identification of micro blisters in paint such as those caused by thermal blistering or solvent blistering in paint
The presence of debris or mold between and in paint layers can be viewed and documented
The photographs and text here show how a paint chip can be prepared for a sectioned or edge-view by either low-power
stereomicroscope, or by high power forensic microscope. Click any photo to see a larger image.
1. Photo of the basic equipment needed to prepare a sectional slice of a paint chip for edge-view microscopic examination.
2. Place the selected paint chip on top of a square of clean 6-mil polyethylene sheeting. The square can be oversized to about 1" x 1" or so as it
will be trimmed later.
3. Place a second square of clean 6-mil poly atop the sample, aligning the edges to make a neat 1" x 1" sandwich of paint chip between the two layers of
plastic.
4. Place the sample sandwich between two clean glass slides and atop a heating plate such as shown in the photo. You may have to experiment to find the
right hot plate temperature to fuse but not over-melt or burn the poly or the paint sample so experiment with non-critical sample material first.
5. This photo shows the poly incompletely fused. More heating was necessary. Our object is to fuse the two layers of poly together so that
the paint chip will be firmly secured between them.
6. When the poly has become sufficiently hot and is melting together we press it gently to remove air bubbles and to
confirm that the two layers of plastic have become fused. There is no problem taking the assembly off of the
heater and then returning it to that surface. Be careful of burns.
7. Here you can see that the poly is nicely fused but not over-melted or bubbling.
8. We cool the sample slides and poly atop a steel spatula used to remove it from the hot plate surface.
9. The sample is immediately numbered with our lab control number again to avoid any possible mix-up. However as we normally prepare,
examine, and photo document one sample at a time there is no real chance for a sample labeling or handling error. Keep sample labels
identical to those used in the chain of custody form and original sample material labels.
10. Trim the sample poly sandwich to approximately 20cm x 20 cm square.
11. A simple stainless steel single-edge razor blade, carefully handled, can produce a sample cross section thin enough for microscopic examination. We will be
using reflected, not transmitted light in most instances with these samples. Cut a thin slice of sample sandwich, 1mm or less in
thickness, keeping the slice oriented so that you don't lose track of which is the edge view.
12. Here is our sliced sample cross-section. The sample side facing up on this slide is not what we want to examine as it
shows the sample face, not its cross section.
13. So we carefully turn the paint sample sectional slice on its side, exposing its cross section. To keep the sample in
the proper orientation, notice that we bent over the plastic ends of the poly sandwich at roughly 90 deg. at each end.
14. The sliced, bent paint chip sample section is placed on a clean microscope slide.
15. As we wanted to make a permanent slide mount of this sample, and as we didn't want any chemical interaction
with the sample, we mounted this cross section of paint chip using clear glass adhesive.
16. Here's our paint sample cross sectional slice mounted in glass adhesive
and with a 50mm x 22mm cover slip, ready for curing.
17. Clear glass adhesive has some nice optical properties, but it needs to be cured by UV light. Rather
than place our sample outside in the sun we used this halogen lamp to harden the slide preparation..
18. Here are some interesting paint chip cross section slices. By calibrating our eyepiece micrometer using a stage micrometer,
we can measure paint layer thickness.
Other photos here are examples of microscopic blistering which was not visible except
at high magnification but quite dramatic when viewed in cross section as shown here. These observations at 120X magnification
and top lighting on our forensic microscope were useful in diagnosing the cause of failure of this paint coating.
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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.
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]
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]
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop, and from the InspectAPedia bookstore. The 2010 edition of the Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.
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]
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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