Like a ghost lurching out of the woodwork, these forgotten images have been brought back to life after being lost to the forces of time.
Using a toolkit of high-tech micro-X-ray imaging techniques, researchers from the University of Western Ontario can now “revive” heavily degraded antique daguerreotypes, an archaic form of photography that used silver plates to capture images.
The new technique, as documented in the Nature journal Scientific Reports, was used to recover two antique photographs from the National Gallery of Canada that were taken some 160 years ago, each depicting an anonymous person posing for the camera.
“It’s somewhat haunting because they are anonymous and yet it is striking at the same time,” lead author Madalena Kozachuk, a PhD student in Western’s Department of Chemistry, said in a statement.
“The image is totally unexpected because you don’t see it on the plate at all. It’s hidden behind time,” continues Kozachuk. “But then we see it and we can see such fine details: the eyes, the folds of the clothing, the detailed embroidered patterns of the table cloth.”
The daguerreotype was invented in 1839 and quickly rose to become the first commercially available means to mechanically capture a visual image. Images are created using a highly polished silver plate that's sensitive to light when exposed to heated mercury vapor, resulting in a silver-mercury imprint of an image on the surface. The technique was revolutionary for the time, even though subjects had to sit still for up to three minutes to successfully imprint the image onto the plate.
However, since many of these images are over 150 years old, the original plates have degraded over time, making them nearly impossible to appreciate. The plates themselves can undergo chemical changes over the decades, further adding to their plight. It was previously thought that tens of thousands of these images could be lost in obscurity, until now.
“Mercury is the major element that contributes to the imagery captured in these photographs. Even though the surface is tarnished, those image particles remain intact. By looking at the mercury, we can retrieve the image in great detail,” added study co-author Tsun-Kong Sham.
The technique uses rapid-scanning micro-X-ray fluorescence imaging to analyze the plates and detect the remaining hints of mercury. Using just this information, the researchers can recreate a new copy of the daguerreotype within a matter of hours. They hope that their new form of imaging could provide curators with a way to restore degraded daguerreotypes, even if the artifact’s condition is beyond traditional conservation treatments.