Seeing Color: Practical Methods in Pigment Microscopy
Palenik, C.S. and Palenik, S.J. (2014) Seeing Color: Practical Methods in Pigment Microscopy. The Microscope v62:2, 51-61.
Published on: 8/1/2014
Microscopical methods permit the pigment particles responsible for color in paints, inks, polymers, rubbers and cosmetics to be directly and readily observed, both in and ex situ. Using examples of pigments in paint, fibers, and cosmetics, practical sample preparation and imaging methods that permit detailed visualization and utilization of pigments as evidence in forensic and industrial examinations will be demonstrated. Preparation methods covered range from the efficient (smears) to the traditional (cross sections) to the state of the art (ion polished cross sections) while imaging methods spanning length scales of millimeters to nanometers, which include polarized and oil immersion light microscopy as well as scanning and transmission electron microscopy will be demonstrated. Not only does such analytical information provide for the opportunity to make observations impossible by more routine, indirect forensic approaches (such as paint comparisons by infrared spectroscopy) or the casual application of magnification that is common in many laboratories (e.g., stereo microscopy of paint chips to determine layer structures), but it opens the possibility to find true differences in finest components of materials, which may be suggestive of a specific manufacturer, batch difference or quality issue. Finally, the resulting images provide a simple and visually compelling means by which to convey such similarities or differences to a lay audience or jury.