Scientific Analysis of Heritage Collections using XRF – Employ.ed Internship 2019

This week’s blog post comes from Cameron Perumal who recently began a 10-week Employ.ed internship in the Conservation Studio at the CRC… 

Two weeks into my Employ.ed internship, and I have already learned so much about conservation, and X-ray Fluorescence (XRF) spectrometry! I am currently an undergraduate Astrophysics student, and my internship entails me working with Emily Hick, the Special Collections Conservator, to research ways in which XRF can help us understand more about the collections. I’ll also be doing outreach to increase awareness on XRF and how it can be used in conservation to improve the condition and understanding of the collections held by the University of Edinburgh.

By the end of my first week, I had started my radiation training, seen the XRF in action being used by another intern, Despoina, to analyse pigments of a painting on the soundboard of a harpsichord, and been able to see the various (frankly, quite beautiful) collections stored by the University.

Intern Despoina using the new XRF machine to analyse the pigments used on the soundboard paintings of harpsichords made by the Ruckers family

XRF, or X-ray Fluorescence, is a non-invasive, non-destructive way of examining and analysing different artifacts in order to produce spectra of their elemental composition. The software does all the elemental composition analysing for you (albeit, there are a few effects that call for manual interpretation). The fun part is interpreting this data, in order to understand more about the object and its context in history. If you know approximately what you are looking for and understand the history behind the material, then XRF can be used on everything from paintings and illuminated manuscripts, to ceramics and glass (as long as it’s safe for the object to be examined).

XRF used to analyse a manuscript

For example, using XRF to analyse paintings can yield information on whether the painting has been retouched, or been painted over because the canvas had been reused – sometimes hiding a completely different painting, as discovered with Picasso’s ‘La Misereuse Accroupie,’ or many of Van Gogh’s works; or it could reveal details about the artist’s palette preferences, which can show where they were based geographically at a certain period of time, based on pigment composition.

The potential of XRF is seemingly limitless, however, there are some limitations to using this analytical method. It can only examine inorganic objects, as radiation cannot be detected from low Z (Z=atomic number) or very high Z elements; it cannot do quantitative analysis; and may have to be used in conjunction with other methods to obtain more specific/detailed results about elemental composition (as it cannot distinguish between ions or the same element with different valencies). The biggest benefit of using XRF is the ability to carry out quick, surface-level analysis to get quick results.

Next week, we get to use the XRF to check whether a collection of British medals are genuine or facsimile, which depends on their metal composition, and if it matches with the composition given in the catalogue of British medals (though we can already visually compare the collection to the medals in the catalogue). I am most definitely looking forward to figuring out how else we can use XRF in a conservation setting.

Collection of framed medals – original or facsimile?

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