Daguerreotype

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Date initiated 	June 2011
Contributors 	Amy Brost, Luisa Casella, Stephanie Watkins
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==Daguerreotype==
=== Historical Facts===
Developed by Nicéphore Niépce and Louis Jacques Mandé Dagyerre following Niépce's experiments with copper coated with asphalt (heliograph).
 
Invented: Introduced January 1839. It was announced on January 9, 1839 to the French Acade,y of Sciences and later purchased and offered by the French government patent-free to the entire world except England.
Main Period of Use: Primarily between 1839-1860. 
Historic Practitioners: Soutworth & Hawes.
Historic Process Variations: M. E. Bequerrel process (1840)
Contemporary Practitioners: Adam Fuss, Rob McElroy, Mike Robinson, Robert Shlaer, Jerry Spagnoli
=== Identification Characteristics===
Image layer: Highlights are silver and mercury amalgam, and dark areas are metallic (reduced) silver. Image particles range from 0.1 tp 50 microns. Plate is often gold toned with gold chloride, which changes rge composition of the image layer, a process that was introduced in 1841. Image is usually laterally reversed, unless when later copied by similar process. Image is a single exposure direct positive.
Plates can be coated using different materials such as isinglass, gum arabic, albumen, gelatine, shellac, waxes, dextrose, or others.
Color: Monochrome image. White haze on surface, sometimes light blue. May have applied color.
Support: Silver plated copper sheet
Analysis: 
UVC illumination may reveal the presence of coatings.
=== Process Overview===
The substrate is a copper plate electroplated with pure silver, polished to smoothness on a series of grinding wheels. Then the plate is sensitized by the vapor of elemental iodine in a sealed box called a fuming box. The plate slides into the fuming box so the photographer is not exposed. Silver iodide is created on the surface of the plate. The plate is placed in a holder and exposed in a large-format camera. The plate is only sensitive to blue/UV light, which breaks the bond between the silver and the iodine. The plate is developed under a piece of amberlith (red printer's screen) creating red light to which the plate is not sensitive, and which enlarges the crystals of free silver, creating the visible image. The less-toxic Becquerel process is used today, eliminating development of the plate using mercury vapor. As such, the surface of the plate is not sensitized with bromines and chlorides. As a result, the Becquerel plates are 10 times slower than traditional plates, making portraits difficult (exposures can be long - more than 5 minutes under strong lights with a fast lens). 
Plates must be fixed after development, and can also be gilded. Ungilded plates are very prone to abrasion and image can be easily wiped off.
Because the exposed surface of the plate is also the final image, the result is a reverse image. The surface is susceptible to tarnish, so glass is placed over the image, with a spacer in between, and the edges are sealed.
=== Conservation and Treatment===
See Cased Photographs
=== Housing and Storage ===
See Cased Photographs
=== Emergency Recovery ===
The image surface of the plate is very susceptible to abrasion and should not be touched. If water emergency occurs, remove from or open case and let air dry. Rinse with clean water if needed.
=== Further Reading===
Conservation
*Barger, M. Susan, A. P. Giri, William B. White, Thomas Edmondson. 1986. "Cleaning Daguerreotypes". Studies in Conservation 31: 15-28.
Process and Historic Material
*Barger, M. Susan and William B. White. 1991 (hardback); 2000 (paperback). The Daguerreotype: Nineteenth-Century Technology and Modern Science. Baltimore: Johns Hopkins University Press. 
*Beaumont, Newhall. 1961. The Daguerreotype in America. New York.
*Coe, Brian and Mark Haworth-Booth. 1983. A Guide to Early Photographic Processes. London: Victoria and Albert Museum and Hurtwood Press 
*Hendriks, Klaus B.; Brian Thurgood; Joe Iraci; Greg Hill. 1991. Fundamentals of Photograph Conservation: A Study Guide. Toronto: Lugus Publications
*Hendriks, Klaus B. 1995. CCI Notes 16/1: Care of Encased Photographic Images. Ottawa: Canadian Conservation Institute
*Nicéphore Niépce House Museum
*Notes on Photographs Daguerreotype entry: http://notesonphotographs.org/index.php?title=Daguerreotype
*Library of Congress, Preservation of Daguerreotype collection: http://memory.loc.gov/ammem/daghtml/dagprsv.html
Contemporary Practice
* Contemporary Daguerreotypes - http://cdags.org/
*See also Cased Photographs bibliography. 
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