In situ analysis of ancient glass: 17 th century painted glass from Christ Church Cathedral, Oxford and Roman glass vessels

Handheld x-ray fluorescence spectrometry (HH-XRF) is a fast and efficient way of analysing samples. It is a non-destructive and relatively inexpensive technique that can analyse large numbers of samples in both laboratory and field environments. There are a number of analytical methods that are capable of analysing glass in a relatively nondestructive way, such as scanning electron microscopy (SEM), x-ray fluorescence spectrometry (XRF) and glass refractive index measurement (GRIM) machines; but these are often not portable and so rely on samples being taken to the laboratory for analysis. Although the actual analysis with these instruments may be nondestructive, limitations relating to the size of the sample chamber often mean that small fragments/ sub-samples need to be removed from the original objects. This means that in situ analyses either in the field or within collections are not possible with these techniques. Glass, either in situ in upstanding windows, or objects held in museum collections often needs to be studied in a non-invasive manner. The idea is to obtain the maximum amount of information possible in one operational action; this may be because of limited access, or due to the fragile nature of the glass. In other cases, it is just not feasible or possible to remove the glass from the current location and therefore a field technique which provides an accurate analysis of the sample is needed. Portable methods are also often preferred in international research contexts, rather than transporting the samples back to laboratories which can entail elaborate, bureaucratic procedures and fees. Portable XRF technology can generally detect major, minor and trace elements within a sample, depending on the nature of the sample and the sample matrix. There are many examples in the literature of the successful use of XRF and portable XRF technology for the analyses of a variety of materials. These include ceramics, metals, rocks and obsidian (a natural glass) with good results. Despite this, portable and handheld XRF technology has been little used for the characterisation of man-made glasses, although laboratory based XRF is often used in these analyses. This paper aims to highlight some of the potential successes and failures of the application of HH-XRF to manmade glass. In order to achieve this and evaluate the potential of HH-XRF in the analysis of archaeological glasses, two studies were undertaken. One study investigated the composition of fragments of Roman glass, while the other study looked at the application of HH-XRF to In situ analysis of ancient glass: 17 century painted glass from Christ Church Cathedral, Oxford and Roman glass vessels