To avoid the problems associated with specifying the exact nature of the heat input from welding arcs, an analogue model is proposed which simulates the quasi-static thermal field produced around the isothermal contour of the molten weld pool boundary during the welding of thin plate. The design of an electrical analogue based directly on Rosenthal's equation (1) governing the quasistatic heat flow about a moving source is shown to be impractical although this approach identifies the physical significance of the two parameter ratios. To overcome the difficulties associated with the direct analogue, a simple transformation of Rosenthal's equation is employed and the design of an indirect or 0 field analogue of this transformed equation is developed. The details of the construction and commissioning of such an analogue are reported. The application of this analogue to studying the quasi-static thermal field is tested by comparing analogue predicted and experimentally measured temperature histories of points in the HAZ for a range of autogenous TIG melt runs on thin mild steel plate. The experimental results are obtained from a purpose built automatic welding rig which incorporates a facility for determining the shape of the molten weld pool during welding. The results from these comparative tests show a good agreement between predicted and measured temperature histories and the application of the 0 field analogue to studying the thermal field during welding is discussed.