A resin system was found to be resistant to the formation of an oxygen-inhibited layer when cured in air via conventional free-radical photopolymerization. The resins, containing multifunctional acrylates and a high concentration of a photoinitiator, were applied as thin film coatings and photocured with either visible light (400-500 nm) or UV light (254 nm). Fourier transforrn infrared spectroscopy with an attenuated total reflection attachment and pencil hardness were used to assess the surface double-bond conversion and the surface hardness of the coatings cured in air and without air, respectively. The surfaces of many tested resins could produce similar conversions under both curing conditions. Optimally formulated resins had a high conversion and hardness even when the irradiance was as low as 50 mW/cm(2) for the visible light and 4 mW/cm(2) for the UV light. The requirements for possessing such a unique curing property are presented. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112:1565-1571, 2009