Some low-modulus birefringent resins

Information is given to enable the photoelastician to select and prepare his own clear, bubblefree, constant-thickness, low-modulus (500 psi or less) birefringent resins. Various urethane formulations are examined. The effects of environment, mixing, casting, molds, cure, post-cure and calibration are discussed. A procedure to select a particular formulation is suggested.