Use of XRF in Ancient Art
Ancient Artefact Validation
The use of EDXRF techniques is a very valuable tool in the world of antiques and archaeology, where the rewards for producing convincing fakes can be high and accurate identification of ancient artefacts is sometimes hampered by subjective judgements based on art styles and manufacturing techniques. Antiquities authentication and the testing and verification of artefacts is a specialized field, since the data produced (i.e. the results of the analysis) have to be interpreted in the light of known genuine results.
Antiquities testing and verification are an important application of XRF technology. The XRF process is used to establish the proportions of the elements present in the object to be tested. The results can be used to study archaeological and historical materials in order to establish likely provenance, fabrication technology and manufacturing technique. These data can help to distinguish non-original material and to detect reproductions and counterfeits.
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The close connection between the mineralogical composition of a ceramic object and the raw material from which it has been formed, as well as the homogeneity of the trace element composition of a single source deposit, allow a precise identification of the probable clay source in many cases. Pigments and other surface treatments on ceramic artefacts can usually be analyzed for their composition. Likewise, residues found inside ceramic vessels can be analyzed to determine what materials the object held and thus how it was used. Ceramics form an important element in dating archaeological strata due to their frangible nature, and pre-modern ceramics are collected for their own sake as unique products of their source cultures; authentication of ceramic antiquities is becoming a common application for XRF technology.
Obsidians are naturally-occurring forms of glass which are produced as igneous rocks. This material was highly-prized in the Mesolithic (Middle Stone Age) because it could be fractured to produce exceptionally sharp blades (microliths) used for knives and arrowheads. In the 20th and 21st centuries, precision surgical instruments have been made from obsidian as its edge is both sharper and finer than that of the best quality surgical steel.
Obsidian sources can be effectively identified by their elemental composition. This is one of the most successful applications of elemental analysis in the history of archaeometry.
In contrast to ceramics, metals do not retain a close chemical connection between the raw materials and the resultant alloy. Metals can be re-processed (re-melted, re-cast and otherwise re-worked) and this factor makes compositionally-based definite provenancing impossible. Nevertheless, combined with other authentication techniqes, elemental composition is a significant indicator in authentication, specifically in identifying non-original parts e.g. in statues and other complex objects. XRF testing of antiquities is becoming a routine procedure for museums and other institutions for this reason.
As with metal alloys, the composition of glass cannot be definitely related to provenance because the material can be reprocessed; ancient glass routinely contains recycled elements (cullet). Here again, elemental analysis can provide important information relating to fabrication technology, specifically as regards the use of different fluxes which can be related to specific geographical areas and historical periods. XRF analysis can determine the colorants, decolorants and opacifiers present in the material and is sometimes used in the verification of antiquities with a significant glass content.