24 albumen photographs, showing views of the cities and forts, 1857-70, from the original Upton negative.
The process of making an albumen print
- A piece of paper, usually 100% cotton, is coated with an emulsion of egg white (albumen) and salt (sodium chloride or ammonium chloride), then dried. The albumen seals the paper and creates a slightly glossy surface for the sensitizer to rest on.
- The paper is then dipped in a solution of silver nitrate and water which renders the surface sensitive to UV light.
- The paper is then dried in the absence of UV light.
- The dried, prepared paper is placed in a frame in direct contact under a negative. The negative is traditionally a glass negative with collodion emulsion, but this step can be performed with a modern silver halide negative, too. The paper with negative is then exposed to light until the image achieves the desired level of darkness, which is typically a little lighter than the end product. Though direct sunlight was used long ago, a UV exposure unit is preferable because it is more predictable, as the paper is most sensitive to ultraviolet light.
- A bath of sodium thiosulfate fixes the print’s exposure, preventing further darkening.
- Optional gold or selenium toning improves the photograph’s tone and stabilizes against fading. Depending on the toner, toning may be performed before or after fixing the print.
Because the image emerges as a direct result of exposure to light, without the aid of a developing solution, an albumen print may be said to be a printed rather than a developed photograph.
The table salt (sodium chloride) in the albumen emulsion forms silver chloride when in contact with silver nitrate. Silver chloride is unstable when exposed to light, which makes it decompose into silver and chlorine. The silver is oxidized into silver oxide during the development process and the remaining silver chloride is washed out during fixing. The black parts of the image are formed by silver oxide. (Wikepidia.com)