*1.4. XRF Imaging Using a Micro Focused X-ray Beam*

It was recently reported that using a micro-focused X-ray beam from a synchrotron light source and selecting the excitation energy to just above the L<sup>3</sup> absorption edge of Hg and tracking the intensity of the Hg L<sup>α</sup> and L<sup>β</sup> lines in a two-dimensional scan across the daguerreotype plate could retrieve the original image from the daguerreotypes tarnished beyond recognition [7]. These results show that it is the integrity of the silver image particles that were formed upon the photochemical reaction of the photosensitizer, silver halide, when exposed to the object, and the subsequent exposure to hot Hg vapor that determines the quality of the daguerreotype [1,2]. Thus, Hg vapor stabilizes the image particles of silver clusters, forming an amalgam that defines the image, and the image particles are preserved by the presence of Hg. If surface reactions or adventitious contaminants such as the organic molecules that tarnish the plate only affect the surface and the near-surface region (on the order of < nm), this would have very little effect on the image retrieved from Hg L<sup>α</sup> fluorescence X-rays. This is also why chemical and electrocleaning would work if the bulk of the image particles remained largely undisturbed after cleaning. The objective of this work is to proceed with chemical cleaning and electrocleaning methods under various conditions on a single daguerreotype plate, and to then conduct Hg XRF imaging to further confirm this notion [3,7].
