A method of manufacturing an optical data storage medium, comprising at least one substrate (11) and a plurality of layers deposited on the substrate (11) is described. The medium includes at least one of a transparent spacer layer and transparent cover layer (12). The layer (12) is provided by applying a liquid onto the rotating substrate (11) and rotating the substrate (11) further in order to spread out the liquid into a layer substantially uniformly between an inner radius ri and an outer radius ro, and solidifying the liquid layer (12) by means of exposure to UV radiation. After applying the liquid onto the rotating substrate the liquid layer (12) is heated by heating means (14) in such a way that the temperature rise of the liquid layer (12) at ri has a value dTri, while the temperature rise of the liquid layer (12) between ri and ro gradually increases, and the temperature rise of the liquid layer (12) at ro has a value dTro>dTri. In this way the spacer layer or cover layer has a variation in thickness smaller than +/−1 μm, measured over the information storage area. Further a medium manufactured using said method and an apparatus for performing the method are described.