This paper examines, by means of a bibliographic search and experimentation, the development of the techniques employed in lead smelting during ancient and historical periods. Using the Phillips EDAX 9500, at the University of Bradford, School of Archaeological Sciences, a series of 24 quantitative analyses was made, and the results used in a discussion of likely modes of slag formation. These problems associated with the production of reference standard, for use with X-ray fluorescence (XRF), are identified and solutions proposed.