AbstractRadiation curing of unsaturated polyester resin‐based compositions offers a number of significant advantages over the use of peroxides and similar free‐radical polymerisation initiators; the cure process can be closely controlled, is usually much faster, and the fabricator is not required to measure out, add, and blend‐in small quantities of catalyst. However most forms of radiation including ultra violet (UV) involve heavy initial expense and the need to provide shielding to protect personnel. Furthermore UV radiation will not usually penetrate deeply into thick glassfibre‐containing compositions owing to the absorption of UV light by both resin and glass.Photoinitiator systems which need only visible light have now been developed however. Using these systems almost any available light source including fluorescent tubes, tungsten filament bulbs and of course natural sunlight and daylight will cause the resin to cure rapidly and completely. By controlling the intensity of the incident light continuous close control of the cure process is easily achieved.The advantages of reduced energy requirements, fast cure,‘one pot’ chemistry and built‐in indicators of degree of cure have already led to a number of special applications for visible light curable pol