Collodion
277502
226039949
2008-07-16T15:42:48Z
161.185.1.100
==Chemical==
'''Collodion''' is a solution of [[nitrocellulose]] in [[diethyl ether|ether]] or [[acetone]], sometimes with the addition of [[alcohol]]s. Its generic name is pyroxylin solution. It is highly [[flammable]]. As the solvent evaporates, it dries to a [[celluloid]]-like film. It was discovered about 1846 by the [[France|French]] chemist and writer [[Louis-Nicolas Ménard|Louis Ménard]].
* Celloidin is a pure type of pyroxylin used to embed specimens which will be examined under a [[microscope]]. [http://www.thefreedictionary.com/celloidin]
==Photography (also known as the Wet Plate Collodion process)==
[[image:summer_guitar.jpg|right|thumb|"Summer w/Guitar" 2005, a contemporary Ambrotype]]
In 1851, the Englishman [[Frederick Scott Archer]] discovered that collodion could be used as an alternative to albumen on glass plates. This also reduced the exposure time when making the image. This became known as the wet plate Collodion or wet collodion method. Collodion was also grainless and colorless, and allowed for one of the first high quality duplication processes, also known as negatives. This process also produced positives, the [[Ambrotype]] and the [[Ferrotype]] (aka Tintypes).
The process was very involved and included the following steps:
* 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]])
All of this was done in a matter of minutes, which meant that the photographer had to carry the chemicals with him wherever he went.
Richard Norris, a doctor of medicine and professor of physiology at Queen's College, [[Birmingham]], is generally credited with the first development of dry collodion plate in the 1860's. In 1894 he took out a new patent for [[dry plate]] used in [[photography]].
==Medical==
*[[Compound W Wart Remover]] consists of [[acetic acid]] and [[salicylic acid]] in an [[acetone]] collodion base used in [[Treatment of warts by keratolysis]].
*Pyroxlin solution is also used presently in [[MedTech]]'s NewSkin [[liquid bandage]] product. <!-- How is it used medically if it is toxic as mentioned above? -->
==Other Uses==
* Collodion is widely used to glue electrodes to the head for [[electroencephalography]].
* Pyroxylin with added [[pigment]]s is used as a [[lacquer#Nitrocellulose lacquers|nitrocellulose lacquer]].
* It was also added to [[nitroglycerine]] to stabilise it as [[blasting gelatine]].
* Collodion is also used in theatrical [[makeup]] for various effects, such as simulating old-age wrinkles or scars.
* Similarly, it was sometimes used in boxing and other applications to cover up cuts. However, it has been generally replaced by Liquid Bandage, which includes pyroxylin as an ingredient.
* Collodion also finds use in the cleaning of [[optical|optics]] such as [[telescope]] mirrors. The collodion is applied to the surface of the optic, usually in two or more layers. Sometimes a piece of thin cloth is applied between the layers, to hold the collodion together for easy removal. After the collodion dries and forms a solid sheet covering the optic, it is carefully peeled away taking contamination with it.
* Collodion was also used by pathologist [[Thomas Stoltz Harvey]] to preserve [[Einstein's brain]] in 1955.
==External links==
* [http://www.collodion.com Contemporary Collodion Photographs and Forum]
* [http://www.jtbaker.com/msds/englishhtml/c5060.htm Collodion: Material Safety Data Sheet]
* [http://home.intekom.com/pharm/sad-otc/comp-w.html Compound W data sheet]
* [http://www.lachambrevolant.com/en/wetcollodion.aspx Brief description of the Wet Collodion process]
* [http://collodion-artist.com Contemporary 19th Century Wetplate Collodion Photography]
[[Category:Nitrates]]
[[Category:Photographic chemicals]]
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[[it:Cotone collodio]]
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[[ja:コロジオン]]
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[[ru:Коллодий]]