Abstract: A heat transfer system includes first and second surfaces which are at different temperatures. A bed of fluidizable material is provided in a cavity which is located between the first and second surfaces, and gas from a supply means is supplied to the cavity to form a fluidized bed from the fluidizable material and thereby to enable heat to be transferred between the first and second surfaces. Control means is provided for alternately forming and collapsing the fluidized bed in order to regulate the rate of transfer of heat between the first and second surfaces. The heat transfer system has particular application in the cooling of a forming mould in a glassware forming system.