Forensic scientist, Washington State Crime Laboratory Public Safety Building, Seattle, WA
(Received 9 October 1987; accepted 15 April 1988)
Many metallic paints, which are commonly used for automotive finishes, can be sampled directly using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The density of metallic flakes used in a particular paint is the primary factor determining the applicability of this method. Specular reflectance, which often limits the usefulness of data obtained from direct DRIFTS sampling, can be mostly eliminated through selective changes in the geometry of the diffuse reflectance accessory. The nature of this direct sampling method depends on the density of the metallic flakes, and a Kubelka-Munk-type reflectance is not the only process involved. For paints having a high density of metallic flakes, spectra of chips as small as 0.5 by 0.5 mm can be obtained. Metallic paints having a basecoat/clearcoat finish can also be sampled using this method, but the clearcoat or primer layer must first be removed.
Paper ID: JFS12620J