Apparatus for ultra-violet light curing by photopolymerization of radiation free ink or coating material, which is coated on the peripheral surfaces of a multi-sided rotatable object: each uncured ink coated object is positioned on a rigid or resilient support at the end of a respective mandrel; the mandrels are rotatably journaled to an endless belt, or the like, which moves the mandrels and the objects supported thereon through a radiation oven; each mandrel carries a wheel, which engages a rack that is oriented parallel to the pathway of the mandrels through the oven such that the mandrels and the objects they support are rotated as they move along the path through the oven; a radiation emitting lamp in the oven is in a plane that is spaced from the axes of the objects as they move through the oven and is generally parallel to the path of movement of the objects through the oven; the lamp is oriented obliquely to the direction of extension of the mandrels and the objects as they pass through the oven to cause uniform radiation impingement along the length of each object on its mandrel. A battery of ovens may be provided through which the objects pass successively.