Paint Analysis Using Visible Reflectance Spectroscopy: An Undergraduate Forensics Lab

The study of forensic science is found throughout undergraduate programs in growing numbers, both as stand-alone courses as well as specific examples within existing courses. Part of the driving force for this trend is the ability to apply common chemistry techniques to everyday situations, all couched in the context of a mystery that must be solved. The paint analysis lab is meant to allow students to determine if paint samples that may appear similar to the human eye are really the same or if they have measurable differences. The forensic aspect of the experiment lies in the application of spectroscopy to determine if the paint sample found at a crime scene is indistinguishable to paint found in a suspect's possession. Since observed colors are due to light reflected from a surface, reflectance spectroscopy is used to analyze the various paint samples. Samples containing various percentages of white and blue paints are analyzed using the 1976 CIELab color space system. As part of this experiment, students learn about reflectance spectroscopy, sampling techniques, basic statistics, and the fact that they can not always rely on initial observations.