Daguerreotype portraits were made by the model posing (often with head fixed in place with a clamp to keep it still the few minutes required) before an exposed light-sensitive silvered copper plate, which was then developed by mercury fumes and fixed with salts. This fixing however was far from permanent – like the people they captured the images too were subject to change and decay. They were extremely sensitive to scratches, dust, hair, etc, and particularly the rubbing of the glass cover if the glue holding it in place deteriorated. As well as rubbing, the glass itself can also deteriorate and bubbles of solvent explode upon the image.
posted by Horace Rumpole
on Jan 8, 2013 -
The Third View project is a fascinating presentation of "rephotographs" of over 100 historic landscape sites in the American West that presents original 19th-century survey photographs, photographed again in the 1970s, then once again in the '90s - from the original vantage points, under similar lighting conditions, at (roughly) the same time of day and year. [Flash, and you'll probably need to allow pop-ups; a little more info inside...]
posted by taz
on Jun 15, 2007 -