Abstract: Process and apparatus for polymerizing oxygen-inhibited ultraviolet photopolymerizable resin-forming material such as a film is shown. The apparatus comprises a pair of U.V. light sources, one being a flash photolysis source, the other a sustained photolysis source, both disposed for irradiating said mass as it abides in an atmosphere such as air which tends to inhibit such polymerization. The process has two essential phases, a superficial phase and a profound phase, performed simultaneously or one in advance of and as preparation for the other. The profound phase is performed with sustained irradiation effective for substantially completely polymerizing said material except for inhibition of polymerization at the surface thereof due to said atmosphere. The superficial phase is performed with flash irradiation effective for forming a tack-free skin over said material.