Photographic emulsion

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Photographic emulsion is a

A solution of silver nitrate is mixed into a warm gelatin solution containing potassium bromide, sodium chloride or other alkali metal halides. A reaction precipitates fine crystals of insoluble silver halides that are light-sensitive. The silver halide is actually being 'peptized' by the gelatin. The type and quantity of gelatin used influences the final emulsion's properties. A pH buffer, crystal habit modifier, metal dopants, ripener, ripening restrainer, surfactants, defoamer, emulsion stabilizer and biocide are also used in emulsion making.

Most modern emulsions are "washed" to remove some of the reaction byproducts (potassium nitrate and excess salts). The "washing" or desalting step can be performed by ultrafiltration, dialysis, coagulation (using acylated gelatin), or a classic noodle washing method.

Emulsion making also incorporates steps to increase sensitivity by using chemical sensitizing agents and sensitizing dyes.

See also

• Nuclear emulsion
• Tintype
• Photoresist

References

• Reilly, James M. (1986). Care and Identification of 19th-Century Photographic Prints. Rochester, NY, USA:
  Eastman Kodak
  .

Further reading

• "Film Emulsion Codes" (PDF). 1.14.
  evertz. 2012-05-01. Archived
  (PDF) from the original on 2017-06-09. Retrieved 2019-06-09.

• Contemporary handcrafted silver gelatin emulsions
• Working with liquid photographic emulsion in a nutshell Archived 2017-02-03 at the Wayback Machine
• "The Big Film Database".