Standardising Portable X-ray Fluorescence for Archaeometry

Portable X-ray fluorescence analysis (p-XRF) has been used in archaeological research for several decades. From the outset, however, the results of this chemical analysis method have been met with great scepticism. There are many reasons for this: for example, objects or types of material have been analyzed for which p-XRF is not suitable, or the results given by the instruments in spreadsheets have been used without critical examination. This has led to a significant number of ill-considered publications that have undermined the credibility of the method in the archaeological community. In addition, this method originated in the field of materials testing (especially for metal scrap) and found into ways into studies of archaeological pottery by way of geology and the specific requirements for the method to analyze this material properly have rarely been studied. One reason for this is that p-XRF is often used by inexperienced personnel with no background in instrument technology, sample chemistry, statistics, etc. In addition, the instruments are very easy to use and always give a result - there is no standardised approach to data collection, evaluation and publication. This was the starting point for this project: a detailed investigation of the instruments and their application to silicate materials (especially ceramics) is long overdue. This includes various instrument studies, e.g. experiments to investigate the influence of environmental conditions such as air pressure, humidity etc. on the measurements themselves, as well as investigations on the material to be analysed. This involves testing how sample moisture, grain size, etc. affect the measurements. At least two different analysers (Niton XL3t/Bruker Tracer 5G) are used to check whether the results of the experiments follow a certain rule or are instrument specific. In addition, the interaction of p-XRF with other archaeometric methods, such as petrography or organic residue analysis, will be investigated in more detail in order to determine their best possible combination. In addition to this experimental aspect, statistical protocols and procedures for data processing and evaluation will also play an important role. Standardised procedures will be developed and made available through R scripts in order to establish standards and guidelines for the definition of precise and accurate p-XRF data and analysis results. To ensure that the project does not operate in a vacuum, all aspects will be discussed and agreed with an international network of p-XRF specialists. At the end of the project, internationally accepted protocols and procedures should be available to strengthen the trust and confidence of the archaeological community in this method.