تسجيل الدخول

تسجيل

SOLVENT AND MICROCHEMICAL TESTS

المؤلف:  Max M. Houck، Jay A. Siegel

المصدر:  Fundamentals of Forensic Science

الجزء والصفحة:  416-417

2026-08-17

24

SOLVENT AND MICROCHEMICAL TESTS

Solvent and microchemical tests (hereafter referred to as “microchemical tests”) have been used to discriminate between paint layers of different pigment and binder composition that are otherwise visually similar. The basis for these tests is that the different layers of paint have a different chemical composition and will, therefore, react differently with oxidizing, dehydrating, or reducing agents. Microchemical tests are destructive; therefore, they should be applied to known samples first to evaluate their utility to specific samples. They should also be used only when sufficient questioned samples are available to avoid consuming the entire sample. Microchemical tests should be performed on the questioned and known materials at the same time and their effects recorded immediately; the effects may develop over time, so effects should also be recorded at intervals for the duration of each test. Additionally, microchemical tests can be applied to peeled individual layers of paint, to avoid interactivity with adjacent layers, as well as intact paint chips. Applying tests this way may make the specific reactions clearer than subjecting an intact chip to the tests. When a chemical is applied, the paint chip or layers may soften or wrinkle, swell, or curl. Entire layers may dissolve or disaggregate. Pigment fillers may bubble or “fizz” or flake apart (called “flocculation”). Apparent color change may be seen in some layers. These traits are not clear-cut results that are easily quantified: They are mainly descriptive in nature but provide good discrimination at the early stages of an investigation and may help to initially classify a paint.