Kaleidoscopic Egg Crate
Anisotropy frozen in a plastic egg tray during the process of molding creates symmetric stress birefringence that is revealed as chromatic retardance patterns. Colors appear at specific rotation angles of the polarized light with transillumination between crossed polarizers. This occurs because the varied optical path lengths in the plastic introduce different retardances that are wavelength-dependent, and thus define the color that is transmitted by the analyzing polarizer. —Samuel F. Pellicori, Calif., U.S.A.