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THE FEBRUARY 21, 2014, issue of Science magazine, published by the American Association for the Advancement of Science, contained a news item titled “Portraits and Their Parasites.”
How could I pass that by?
It turns out that scientists now understand why 19th-century daguerreotype photographs grow fuzzy. What’s more, the mechanism of this fuzziness has implications extending backward as well as forward in time.
It got me interested in this scientific news as well as daguerreotype history and technique.
The era of the daguerreotype was surprisingly brief, from 1837 to the 1860s. French artist and chemist Louis Daguerre extended the work of earlier inventors seeking means of chemically capturing and preserving an image.
The process of exposure, development and fixation of a traditional photo was complex, particularly so for a daguerreotype. A highly polished silver surface was exposed to iodine fumes, thus producing a silver iodide coating. This was done under a safelight, a light with frequencies to which the coating was insensitive. The plate was then put in a light-proof case and later exposed to the focused image through a camera’s lens. At first, these “exposure” times were measured in hours.
Daguerre’s crucial discovery was the step of “developing” a shorter exposure’s invisibly faint image by enhancing it in the presence of a heated mercury vapor.
Last, the resulting visible image was “fixed,” that is, made insensitive to further light, by removing the unaffected silver iodide with a heated concentration of salt water. Later, fixation used a more effective “hypo,” a hyposulphite of soda now known as sodium thiosulfate.
Particularly as practiced in the 19th century, the process was anything but environmentally friendly.
An early Paris street scene, “Boulevard du Temple,” had an exposure time of more than 10 minutes, thus missing the images of anything in motion. Apparently, though, a fellow getting a street-corner shoeshine stood immobile long enough to be captured.
Plenty of people posed for daguerreotype portraits, among them the Duke of Wellington and Presidents Andrew Jackson and Abraham Lincoln. By contrast, the civil war photographs of Matthew Brady and his associates were albumin prints on glass, one of several evolving technologies less expensive than daguerreotypes.
By the 1860s, daguerreotypes were old fashioned technology—not unlike film in our digital world. However, like film photography, daguerreotypes retain a cult status, including the 2013 ImageObject Exhibition in New York. See the Cdags.org Facebook page at http://goo.gl/A Qzbpk.
“Portraits and Their Parasites,” in Science magazine, February 21, 2014, traces the fuzziness of old daguerreotypes to fungi and other unidentified life forms eating the surface of the photo. They digest the metals and excrete nanoparticles of gold and silver that disfigure the image.
The fungi and other life forms offer clues as to where an unidentified daguerreotype was made. Researchers also note that the parasites may offer biological techniques for the manufacture of nanoparticles.
Both the past and the future become less fuzzy. ds
© Dennis Simanaitis, SimanaitisSays.com, 2014