A spectroscopic study of paint

Abstract

Paint is one of the commonest forms of trace evidence submitted to a forensic laboratory for analysis. It is essential that techniques are available that allow rapid and confident discrimination between different samples. The aim of this study was to ascertain the discrimination that could be achieved between twenty white architectural paints (water- and solvent-based), and fourteen white automobile paints (primers, topcoats and refinishes). A variety of destructive and non-destructive analytical methods were investigated. These included visual microscopy, wet chemical tests, thin layer chromatography (TLC), infrared spectroscopy (IR), Raman spectroscopy and pyrolysis-gas chromatography (Py-OC). Attenuated total
reflectance (ATR) IR spectroscopy provided non-destructive discrimination between the majority of architectural and automobile samples. Raman spectroscopy - a technique that could have far-reaching forensic applications in the future - allowed the discrimination of approximately half of the automobile paints. Using a combination of analytical techniques, it
was possible to discriminate between 92% of architectural paints and 93% of automobile paint samples.