Posted on 06/23/2018 1:40:04 PM PDT by BenLurkin
Invented in 1839, daguerreotype images were created using a highly polished silver-coated copper plate that was sensitive to light when exposed to an iodine vapour. Subjects had to pose without moving for two to three minutes for the image to imprint on the plate, which was then developed as a photograph using a mercury vapour that was heated.
Kozachuk conducts much of her research at the Canadian Light Source (CLS) and previously published results in scientific journals in 2017 and earlier this year. In those articles, the team members identified the chemical composition of the tarnish and how it changed from one point to another on a daguerreotype.
"We compared degradation that looked like corrosion versus a cloudiness from the residue from products used during the rinsing of the photographs during production versus degradation from the cover glass. When you look at these degraded photographs, you don't see one type of degradation," said Ian Coulthard, a senior scientist at the CLS and one of Kozachuk's co-supervisors. He is also a co- author on the research papers.
Kozachuk used rapid-scanning micro-X-ray fluorescence imaging to analyze the plates, which are about 7.5 cm wide, and identified where mercury was distributed on the plates. With an X-ray beam as small as 10x10 microns (a human scalp hair averages 75 microns across) and at an energy most sensitive to mercury absorption, the scan of each daguerreotype took about eight hours.
"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," said Tsun-Kong (T.K.) Sham, Canada Research Chair in Materials and Synchrotron Radiation at Western University. He also is a co-author of the research and Kozachuk's supervisor.
(Excerpt) Read more at phys.org ...
I have a daguerreotype of my 3rd great grandmother Elizabeth Young Hiter, taken when she was quite old. On the back my great grandmother identifies her as her childrens’ great grandmother. Elizabeth’s great grandmother was Mary Hawkins Craig, one of half a dozen female Revolutionary War Patriots.
I wonder if photographers developed neurological damage.
My great grandfather’s middle name was Hiter (Thomas Hiter Crouch), first Baptist minister in East Tennessee. He was known as Hiter, since he had an older brother named Thomas.
Photographers did develop a lot of problems as did hatters who used mercury vapor in the production of hats. Hence the phrase “mad as a hatter”.
We are no doubt cousins. This branch was separatist Baptist. The Craigs and the Travelling Church.
As the Bible says, He will bless the family unto the fourth generation.
I have one of my grandmother that is still very visible.
She’s lovely. Love seeing these old photos.
This story of recovery reminds me of the time, back in the day, when NASA, or the equivalent back then, put cameras on board rockets and sent them to take pictures of the stars above the turbulence of the upper atmosphere. The film was then parachuted back to earth a developed.
On one mission, the camera lens was mistakenly stopped way, way, down and when the film was developed there was little of use because it was too late to over-develop in compensation.
They gave the black and white negatives to a girl at an Alabama army base to do what she pleased with it.
She exposed the film to radiation, making the silver atoms that formed the images radioactive. Then she made contact sheets using the radiation as the only light source, and saved the day.
Thanks BenLurkin. Although very much a modern history topic, this looks like a great idea for the weekly digest ping.
Like almost all American Jews, I have no record of my family beyond my grandparents. Every other record or photo was destroyed by the Nazis.
:’(
Reminds me that the scientists keeping teasing us with stories about their progress in deciphering the library scrolls that were burned in the library of Piso (?) at Herculaneum.
(I remember it was somebody The Elder. :-) but didn’t look it up and took a short. Damn dementia.)
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