Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Chemistry

Supervisor

Sham, Tsun-Kong

2nd Supervisor

Martin, Ronald R.

Co-Supervisor

3rd Supervisor

Nelson, Andrew J. & Coulthard, Ian.

Affiliation

Coulthard, Ian. (The Canadian Light Source, Saskatoon, SK)

Co-Supervisor

Abstract

The first commercially viable photographic image, the daguerreotype, captured images from 1839 to 1860. While daguerreotypes provide a significant historical record of 19th century individuals and events, deterioration now disfigures many of these images. This work describes the application of synchrotron radiation (SR) to the study of daguerreotypes.

Three goals were addressed in this thesis: 1) to utilize SR to further elucidate the physics and chemistry of the daguerreotype and how the surface varies with time, 2) to study the effects of the electrocleaning system on the daguerreotype surface, and 3) to propose suggestions to improve their preservation and restoration efforts.

The collection of the Ag and Au L3-edges from a daguerreotype test plate showed that the image particles on the surface form an alloy with a fcc structure and that the degree of Au diffusion into the Ag plate differed across the surface. This variation in diffusion produced an average alloy composition of Ag90Au10 (shadow and midtone regions) and Ag73Au27 (highlight region). Finally, both lab and SR sourced X-ray photoelectron spectroscopy showed Hg was present only within the first 1-2 nm of the surface and that alloying with Ag was possible but not consistent across all regions.

Expanding to 19th century plates, the primary tarnish on the surface was Ag2S and AgCl. X-ray fluorescence (XRF) found S and Cl to accumulate on high-density image particle regions. S K-edge suggested a possible Hg-S interaction, corroborating minimal amalgamation between Hg and Ag.

XRF of the eye region noted a variety of deterioration compounds and blemishes, which were removed when treated electrochemically by both the Barger (1982) and Wei (2011) methods. Full plate XRF imaging revealed that while the Hg L emission retained a great deal of information both before and after cleaning that Au and Hg were removed: the Barger method had the greatest impact on the relative concentrations of Au, while Hg appears to be removed in similar quantities by both the Wei and Barger process. Importantly, this work presents a method that allows, for the very first time, the retrieval of fine daguerreotype images tarnished beyond recognition.

Summary for Lay Audience

The research described in this dissertation concerns the analysis of 19th century daguerreotypes. The project had three goals: 1) to gain a deeper understanding of the physics and chemistry of the daguerreotype surface and how the surface degrades with time, 2) to develop alternate methods for preserving the content of these images by refining existing electrocleaning systems, and 3) to make specific recommendations for the preservation and restoration of historically significant daguerreotypes.

The first goal was addressed by using X-ray absorption near edge structure (XANES) spectroscopy to study a freshly prepared reference daguerreotype. The results suggest that inter-diffusion of gold and silver leads to the development of a silver-gold alloy, whose composition varies across the surface and with depth. This was confirmed with laboratory and synchrotron-based X-ray photoelectron spectroscopy. Subsequently, 19th century daguerreotypes were examined with XANES spectroscopy and X-ray fluorescence (XRF) microscopy. This provided information on the elemental distribution and speciation of tarnish on the daguerreotype surface. Finally, completely obscured daguerreotypes, were retrieved with rapid scanning, synchrotron-based micro-XRF imaging. Importantly, this rapid scanning imaging provides curators with an image recovery method for degraded daguerreotypes, even if the artifact’s condition is beyond traditional conservation treatments, and fulfills part of the second goal of this thesis.

The second goal was fully accomplished when a more effective electrocleaning system was developed and produced in collaboration with John McElhone at the National Gallery of Canada (NGC). This enhanced system and was subsequently used to treat 19th century daguerreotypes with two different electrocleaning methods: the original method proposed by Barger (1982) and a second put forward by Wei (2011). Micro-XRF, at both specific regions and across the entire plates, revealed that when used correctly, both processes significantly reduced the sulfur and chlorine surface contamination without dulling the surface. However, both electrochemical methods used in this study resulted in a loss of mercury and gold from the surface.

Specific recommendations for the preservation and conservation of these historical photographs (Goal 3) are discussed throughout and in the conclusions chapter of this thesis.

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