Birefringence

At the 4C's (Columbia Council of Camera Clubs) Photography Convention this past weekend, we got a chance to experiment with photographing birefringence in plastic objects. A sheet of polariing film was placed on a light table, then the plastic object(s) and a camera polarizer or another sheet of film was used to bring out the very colorful optical effect. Cool, huh?
Examples below (click to enlarge):