New Technology Revives Tarnished Daguerreotype Ghosts
The very first
photographic images and the technique that created them were formally
introduced to the world on Aug. 19, 1839, in a scientific lecture to a
breathless, jam-packed audience at the Institut de France in Paris. Details of
the technique revealed that a silver-coated copper plate cleaned with nitric
acid was iodized, exposed in a camera and an invisible, latent image was then
revealed by exposure to heated mercury vapor. Pretty cool, huh?
Eponymously dubbed the
daguerreotype after its inventor, the French artist and illusionist, Louis
Daguerre, these seemingly magical and amazingly precise images marked the
beginning of photography and the first "true" or exact visual
portrayals of history. The French government released Daguerre's process into
the public domain and within months the daguerreotype became a worldwide
sensation. Between 1839 and the late 1850s (when the technology advanced to
glass plates and eventually to paper negatives) millions of images were
captured as daguerreotypes.
Over time (like 179
years already) daguerreotypes are prone to tarnish. Other chemical reactions
result in black spots and fogging (a white and blue-tinted haze) that can cause
the image to deteriorate from beyond recognition to no longer visible, or
completely obscured. But luckily, there's more to this picture than meets the
eye: Science to the rescue!
An interdisciplinary
team of researchers from Canada's University of Western Ontario, the
Photography Institute at the National Gallery of Canada and the Canadian Light
Source (CLS), using facilities at the Cornell High Energy Synchrotron Source
(CHESS) conducted a detailed analysis of the chemical changes that degrade and
potentially destroy daguerreotypes. Their study, published June 22, 2018, in
Scientific Reports, reveals that by looking at the mercury content of
individual daguerreotypes, researchers can retrieve some images in great
detail.
What they found was
that in some cases, even the images on severely tarnished daguerreotypes can be
recovered. Using scanning X-ray fluorescence (XRF) to determine the elemental
makeup of the daguerreotype surface, the team discovered that the mercury
distribution alone, as retrieved by scanning XRF, closely reproduces the
original image and isn't affected by certain kinds of degradation tarnishing.
Because mercury is the major element that comprises the images, even though the
surface of the daguerreotype is tarnished, the image particles remain intact.
The XRF method is
noninvasive and doesn't touch the fragile surface of the daguerreotype or alter
it in any way. That's great news for museum curators, conservationists,
scholars and historians who seek to preserve the world's earliest photographic
cultural artifacts.
And it's a fly in the
face of immortality for the 19th-century mercurial ghosts who lie latent on
tarnished, silver-coated copper plates, waiting to be unforgotten.
source:
https://electronics.howstuffworks.com/x-ray-fluorescence-technology-revives-tarnished-19th-century-images.htm
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