Albumen print
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The albumen print, invented in 1850 by Louis Dsir Blanquart-Evrard, was the first commercially exploitable method of producing a print on a paper base from a negative. It used the albumen found in egg whites to bind the photographic chemicals to the paper and became the dominant form of photographic positives from 1855 to the turn of the century, with a peak in the 1860-90 period.
The process is as follows;
1) a piece of paper is coated with an emulsion of egg white (albumen) and salt (usually sodium chloride). The albumen tends to seal the paper and create a slightly glossy surface.
2) the paper is then dipped in a solution of silver nitrate and water which makes the paper light-sensitive.
3) the paper is then dried in total darkness.
4) the dried prepared paper is then placed in a frame under a glass negative and exposed to light. Often, it is a glass negative with a collodion emulsion. This is exposed to direct sunlight until the image achievs the proper level of darkness.
Albumen prints are placed in direct contact with the negative. Since the image emerges as a direct result of exposure to light and without the aid of a developing solution, the albumen print is a 'Printed' rather than 'Developed' photograph.
A bath of Sodium thiosulfate then fixes the prints exposure and prevents further darkening. Finally, gold toning improves the photographs tone and helps protect it from fading.Template:Photo-stub