The Collodion Process

Collodion is a chemical, discovered in 1846, (see the Wikipedia entry on collodion: http://en.wikipedia.org/wiki/Collodion), and used in one of the first photographic processes, aptly named the collodion process, also known as the wet-plate process because it involves pouring of liquids onto a glass plate (Schimmelman, The Tintype in America 1856-1880, p. 13). Frederick Scott Archer first published information about this collodion process he was working on in 1851, which was notable because it created a glass plate negative rather than a positive (Schimmelman, 13). The Daguerreotype, which was popular at the time, created a single positive image. The negative created in the wet-plate collodion process could be used to create positive prints (which are called Ambrotypes [on glass with a black backing] and Tintypes [on dark metal]). Positives could also be printed on paper, such as albumen paper. These negative glass plates were also notable because the prints they created were of high quality (Schimmelman, 13-14).


According to Robert Leggat, on his Web site, which includes an interesting discussion of the history of the collodion wet-plate process, the process was faster and cheaper than other early photographic processes, which led to its popularity in the United States. Though, apparently it was also messy and not very easy to do because initially the whole process, including developing, had to happen in about ten minutes. And it was explosive. Oh, and also, because Archer didn't ever patent his process, many people were able to just do it for free, which added to its popularity (Robert Leggat, “The Collodion Process in A History of Photography, http://www.rleggat.com/photohistory/history/collodio.htm).



It was most popular from the 1850s until the 1880s, according to the Getty Museum’s Web site, which also has a video that gives a nice sort of re-enactment of the wet- plate collodion process: (http://www.getty.edu/art/gettyguide/videoDetails?cat=2&segid=1726).


The Wikipedia article on collodion lists the steps to the wet-plate collodion process
(http://en.wikipedia.org/wiki/Collodion):

* Clean the glass plate (extremely well)
* Flow the glass plate with "salted" (iodide/bromide) Collodion
* Immerse the plate in a silver nitrate bath (for 3-5 minutes)
* Expose the plate (can range from less than a second to several minutes)
* Develop the plate (using an iron based developer)
* Fix the plate (with potassium cyanide or sodium thiosulfate)
* Varnish the plate (with a varnish made from gum sandarac, alcohol and lavender oil).

In terms of the unique aesthetics of the collodion process, Schimmelman writes that the paper prints (photographs) made by the process had “the familiar look of a monochromatic wash drawing on paper, an advantage for those who by their creative energy wanted to nudge photography toward fine art” (14).

A dry-plate collodion process was created a few decades later, in 1871 by Richard Leach Maddox, according to an article, “The Preservation of Glass Plate Negatives,” by Greta Bahneman (http://www.webjunction.org/470/articles/content/439665.) This process was chemically a little bit different and basically allowed the photographer to develop the negative glass plate later, which gave them more flexibility. Bahneman gives a very detailed analysis of preservation concerns when handling the glass plates (wet and dry), and even includes a section on digitizing, suggesting that it needs to be done for preservation and access purposes, and can be completed with either a flat-bed scanner or a digital camera.

In terms of preservation and digitization, obviously the fact that the negatives are glass poses some problems.

Here is a discussion on photo.net, in which someone is asking for advice about scanning glass plate negatives: http://photo.net/digital-darkroom-forum/00QH6E . There doesn’t seem to be a real consensus about best practices for these. People on this discussion board don’t think that making prints of the negatives first, and then digitizing the prints is very necessary, or cost-effective for an organization without much money. Some said that the negatives could be digitized on scanners, but they have to be handled very carefully.

The glass can also cause reflections during the image-capture. This page from the Bancroft Library (http://bancroft.berkeley.edu/collections/casedphotos/digitization.html) describes a digitization project involving ambrotypes, and the problems faced because of the reflective surface of the glass. They were using a digital camera for this project.

According to this page, “Preservation issues in digitizing historical photographs,” created by the European Commission on Preservation and Access, which lists SEPIA (Safeguarding European Photographic Images for Access) Guidelines for preservation when digitizing old photographs, ambrotypes and tintypes are quite sensitive to abrasion as they do not have the protective covering that daguerreotypes have (http://www.knaw.nl/ecpa/sepia/workinggroups/wp4/guidelines.html).


Print source:
Schimmelman, Janice G. The Tintype in America 1856-1880. Philadelphia: American Philosophical Society, 2007.