We recently had the pleasure of a visit from our colleague David Scott. David is a faculty member in the Department of Art History and Chair of the UCLA/Getty Conservation Program. He’s also our local expert on inorganic pigments so we were delighted to welcome David to our lab with his portable XRF machine to help us analyze the illuminations on a few of our Armenian devotional scrolls.
Prof. David Scott setting up a portable XRF
The portable XRF is a fantastic device that allows for non-destructive micro-testing of pigments. “XRF” stands for X-ray florescence. An XRF spectrometer illuminates a sample with an X-ray beam that is scattered and absorbed in a manner that depends on the chemistry of the sample. This used to require bringing artifacts to the XRF and placing it inside a lead chamber for testing. The logistics of transportation are sometimes obstacle enough, to say nothing of trying to place a scroll inside a lead chamber.
The portable XRF devices that are now available let the X-rays come to the object. A small vacuum is created at the head of the XRF to hold the sample area in position and then a very finely targeted beam of X-rays is directed on the sample. The fluorescence data is transmitted to a laptop computer and the spectra are compared against the known elemental spectra to find a likely match.
XRF testing on an Armenian Scroll
Once we got done bombarding David with questions, in just a few minutes he was rattling off a list off elements on our scroll. The XRF turned up lots of arsenic, lead and mercury, but those don’t account for the whole range of colors we see on the scroll. Our hunch is that there are some organic pigments that we need to account for, also. For instance, we suspect that there is a blue color made from indigo. The plant-derived (organic) indigo pigment is non-elemental, so it would not show up using XRF, but it would be possible given the place of production and with the yellow arsenic, would provide a green. So, there’s more analysis and testing to come, but going from nothing to a positive identification of numerous minerals inside of a couples hours? That feels like magic.
Thanks to Professor David Scott for his help with this project. We’ re looking forward to more!