This year we were fortunate to be loaned a handheld X-ray fluorescence spectrometer for six weeks by Bruker AXS. Before we started to use it, Dr. Bruce Kaiser taught a most informative two day workshop on the technology to ten archaeologists and conservators working with the INSTAP-SCEC. The workshop included lessons on basic theory, how use settings and filters to optimise the equipment for different materials, much advice on interpretation, and lots of hands-on testing. This was a fantastic chance for us to see the technology and test it in our workplace.
Since the introduction of relatively inexpensive handheld equipment, XRF has become a common tool in museum and archaeological field laboratories. The Bruker unit is particularly used by conservators and researchers in obsidian sourcing and glass studies. Visually a bit like a ray gun, a handheld XRF unit contains an X-ray tube which produces a narrow beam of targeted low energy X-rays. Interacting with the surface of an artifact, these produce secondary X-rays which are reflected back into the unit and measured. A laptop connected to the unit displays an instant, easily interpreted result; the elements of which the artifact is made. The technique is entirely non-destructive and most elements (even light ones such as sodium and chlorine) can be detected. Semi- quantitative analysis is possible if standards are used.
This additional layer of information elemental composition provided by XRF means that many questions can be quickly answered in the conservation laboratory or the field (handheld XRF is often used for soils on site). Some examples of problems explored during the workshop were: What colour was this ancient glass originally?; Is this obsidian from Melos or elsewhere?; Is this metal artifact pure gold/silver/copper or is it alloyed with other metals?; What is the corrosion product on this silver object?; What level of damaging chloride ions are present in this artifact? Building on elemental data, informed choices on further analytical techniques or conservation treatments can be made.