Elissa Hulit


The use of portable X-Ray fluorescence spectrometry in the study of prehistoric ceramics has gained popularity recently due to the many benefits of this technology. Portable Energy Dispersive X-Ray Fluourescence (XRF) is non-destructive, relatively inexpensive, and capable of detecting a range of the elements that commonly distinguish clay bodies. It has been used successfully as a means of differentiating prehistoric pottery from different sources and has provided new insights into pottery manufacture and trade networks. However, when it comes to clay sourcing, the high degree of sensitivity in XRF analysis may present new challenges that must be considered before XRF can be used effectively. Natural clay deposits can be expected to vary in composition as the result of formation or deposition processes. During pottery production, humans introduce new sources of compositional variation at various stages of manufacture. While the compositional variation resulting from the subtraction of natural inclusions and from the addition of tempering materials and decorative slips or paints has received attention, no attempt has been made to determine if XRF alone has the capability to identify compositional variation resulting from different fire temperatures. This paper presents an attempt to identify such differences between a set of control samples. These vessels were made from the same stock clay, but vary in tempering materials and firing temperatures. A principal components analysis of the compositions suggests that chemical changes as a result of firing temperature can be detected by the XRF device. Clay sourcing studies using XRF technology should take this source of variation into account. Furthermore, the interaction between firing temperature and the temper material indicates that while knowledge of the pottery firing temperature may be needed, knowledge of how the tempering material reacts to firing atmosphere may also help refine clay sourcing methodology.