View Full Version : Photographic Emulsions

Photo Engineer
06-07-2010, 08:27 PM
I was idly doing a search on GOOGLE looking for references to Photographic Emulsions when I found several items that classed Cyanotype and other Alternate photographic systems as "Photographic Emulsions".

I feel it necessary to dispel those myths or misstatements.

See my definitions thread first then consider this....

A photographic EMULSION is the suspension of Silver Halide in Gelatin. As an example, CYANOTYPE is a clear solution of several chemicals in water with no gelatin. Gelatin can be added to aid in coating, but is not necessary. In current photo systems, gelatin or substitutes are needed components.

It is clear to me that the people using the terms are not clear on the correct usage.


06-07-2010, 10:54 PM
As long as I have been doing Pt/Pd (12-14 years) people who should know better have referred to Pt/Pd/ferric oxalate solutions as "the emulsion". I know not why.

Kirk Keyes
06-07-2010, 11:05 PM
Well, keep in mind that the term "emulsion" is used incorrectly and it is a misnomer.

The definitions of emulsion and suspension are:
• Emulsion - A mixture of two or more liquids that are not soluble in one another. One is suspended as small droplets in the other.
• Suspension - A suspension is a colloidal dispersion (mixture) in which a finely-divided solid is combined with another liquids, with the former being so finely divided and mixed that it doesn't rapidly settle out.

Despite the name, photographic emulsions are actually a suspension of finely divided solid silver halide crystals in a mixture of gelatin and water. But since the term "emulsion" is so entrenched in photographic history, tradition, and literature, there is no need to try and change the usage.

Photo Engineer
06-08-2010, 08:33 AM

See my definitions thread. I address this curious anomaly.

In photographic science, the definitions of emulsion and dispersion are reversed. They have been ever since the beginning. And, I believe that this is true regardless of language.