Speaker: Tsun-Kong (T.K.) Sham, Western University, Ontario
Abstract: An overview of the recent success of using X ray fluorescence (XRF) imaging excited with a tunable X-ray microbeam from synchrotron light sources for the recovery of damaged and obstructed 19th century daguerreotype will be presented. [1, 2] Daguerreotype is the first commercial photography in human history (early 1800’s) produced on a polished, silver coated copper plate. We show that high quality images can always be retrieved from tarnished plates using Hg L XRF as long as the bulk of the image particles and their distribution remain intact. This technique overcomes the challenges of conventional conservation methods which are often unable to bright the image back to life. We also report results from using tunable tender X-rays (2 - 7 keV) to image in high vacuum at energy above the Ag L-edge and the Hg M-edge, extracting images using Ag L and Hg M, respectively among others (e.g., S to track corrosion). Images obtained with the surface sensitive total electron yield (TEY) and the bulk sensitive fluorescence yield (FLY) as well as corresponding micro-XANES are noted. Flux tolerance to high intensity X-beam is also explored. These results and their implications for cultural heritage and other cultural heritage research and prospects of the technique at fourth generation light sources will be discussed.
1. Kozachuk, M.S.; Sham, T.K.; Martin, R.R.; Nelson, A.J.; Coulthard, I.; McElhone, J.P. Recovery of Degraded-Beyond Recognition 19th Century Daguerreotypes with Rapid High Dynamic Range Elemental X-ray Fluorescence Imaging of Mercury L Emission. Sci. Rep. 2018, 8, 1.
2. Stark, A; Filice, F.; Noël, J.J.; Martin, R.R.; Sham T.K.; Finfrock, Y.Z.; Heald, S.M. Retrieving Tarnished Daguerreotype Content Using X-ray Fluorescence Imaging-Recent Observations on the Effect of Chemical and Electrochemical Cleaning Methods, Herit. Sci. 2021, 4, 1605-1615
*Research conducted at Western University is supported by NSERC, CFI, CRC of Canada and OIT of Ontario and Western University