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Forensic Paint Microscopy (1715)


Course schedule: 8:00 a.m. – 5:00 p.m. Monday – Thursday, and 8:00 a.m. – 12:00 p.m. Friday

Paint fragments are sectioned and studied by transmitted polarized light and epi-fluorescence microscopy. Proficiency in polarized light microscopy is assumed and necessary. Inorganic pigments and extenders are identified by morphology, optical crystallographic properties and qualitative microchemical tests.

Microchemical reactions and sublimation methods are used for characterization of organic pigments and identification of some polymer binders. This course also reviews optical crystallography (as needed for the determination of optical properties of inorganic extender and pigment sublimate crystals) and high magnification/resolution microscopy using oil immersion objectives.

Prerequisite: course 1201 or equivalent

Day 1
Review of polarized light microscopy; Nature of paint: chemistry of vehicles and pigments, history, different kinds of paint, particle size

Day 2
Köhler illumination, Micrometry, Refractive index measurements, Pleochroism, Dispersion staining, Extinction, birefringence, compensation

Day 3
Sampling and sample handling: tungsten needles, crossections, mounting media, crushings; Preparation of samples for FTIR, SEM (EDS); Particle identification and characterization of pigments: Morphology, optical properties, observations on <11 um particles, Aroclor preps in 5442 and 1260 (rolling media), high index methods, S/Se melts and sublimation

Day 4
Microchemical methods; Sample preparation, ashing, fusion (Na2CO3), solubility, density, qualitative inorganic and organic analysis, microminaturization of tests; Vehicle examination and identification: Media, surface coatings, glues, pastes, solubility, staining, fluorescence

Day 5
Special methods: FTIR, fluorescence, SEM, TEM; Interpretation/Resources: significance of correspondence, survey data, standards, case circumstances