Description of properties and the method of processing of the photoelastic model material, which is suitable for casting three-dimensional photoelastic models, is presented. The material exhibits a negligible 'rind' effect, very small residual birefringence and an excellent machinability. The important feature of the material is the possibility to control the exothermicity of the polymerization even in very large castings. © 1990 Society for Experimental Mechanics, Inc.