Earliest photographs analysed at the ESRF
The oldest recorded daguerreotype photograph dates to 1839. The method of photography became widely available through the 1840s and was especially popular in the 1850s before being replaced by updated technology in the 1860s. At the height of their popularity they were a novelty, offering the first alternative to a painting or drawing and often given as gifts inside pendants for example.
Like many photographs, the quality of the image has faded with time, however, whereas more recent forms of photography offer the potential for replica copies such as with negatives, or more recently, digital copies, in the case of daguerreotypes, only one of each image was made. This makes the conservation effort even more important because many valuable and irreplaceable artistic (e.g., portraits) and historical (e.g., American civil war) documents have been made using daguerreotypes.
A team from the University of Antwerp (Conservation Studies and the EMAT-research group) and Ghent University (XMI-research group) brought their daguerreotype photographs to the ESRF to scan them on the Dutch-Belgian BM26A beamline which is dedicated to X-ray absorption spectroscopy. They were looking to gain a greater understanding of the corrosion occurring to the photographs, both in terms of natural factors, such as pollutants and humidity damage, and also the effect of cleaning methods on the samples.
The Daguerreotype inside its original case. The daguerreotype is protected by a cover glass and an air tight package but over time H2S diffused slowly into the package, resulting in a tarnishing of the silver-based image. Credit: Eva Grieten.
Using X-ray Absorption Fine Structure Spectroscopy the team observed an underlying layer of corrosion in addition to the surface layer. Understanding what is happening to the sample is important for working out the best action to take.
One option is to clean a sample and exposure to cyanide and thiourea are examples of more traditional cleaning techniques. However these methods may cause damage to the microstructure of the daguerreotype or can instigate future corrosion. Until now in fact, no satisfactory cleaning method exists for the treatment of (coloured) daguerreotypes. Therefore, museum conservators are constantly looking for new and improved cleaning methods that are able to remove corrosion products without altering the original microstructure. One of the most promising cleaning methods being considered, is an afterglow generated by a plasma at atmospheric pressure, a technique that was discovered several years ago and further improved in the EU-project PANNA (www.panna-project.eu).
At the ESRF, the team led by Olivier Schalm from the University of Antwerp observed the daguerreotype after it had been applied with the cleaning treatment and saw that only the copper corrosion compounds, which had developed on the surface, the corrosion, endured a chemical reduction, whereas the gold coated nanoparticles responsible for the image formation were not changed. Visually, the readability of the image has clearly been improved.
Example of a daguerreotype before (left) and after (right) treatment with a reductive afterglow. The afterglow is able to improve the readability of the faintly tarnished zones such as the central person such as the garment and the arms. Credit: Patrick Storme
Lead author on the paper Olivier Schalm from the University of Antwerp said:
“This information will be of vital importance for conservation efforts and might allow future generations to still have access to the visual record from the early days of photography. It shows that this form of cleaning isn’t damaging the sample itself, but just eliminating some of the corrosion products that have occurred which is exactly what conservators are looking for”.
The research team was composed of: Olivier Schalm1, Eva Grieten1,2 *, Pieter Tack 3, Stephen Bauters 4, Alessandro Patelli 5
1. Conservation Studies, University of Antwerp, Blindestraat 9, B-2000 Antwerp, Belgium
2. EMAT, Department of Physics, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
3. XMI, Ghent University, Krijgslaan 281, 9000 Ghent, Belgium
4. DUBBLE-CRG, European Synchrotron Radiation Facility (ESRF), FR-38043 Grenoble Cedex, France
5. Veneto Nanotech, Via delle Industrie 5, 30175 Marghera, Venezia, Italy
* Provided the daguerreotype.
More details about this and other work involving the ESRF can be found in the latest copy of ESRF News.