Page "Collodion process" Paragraph 21

The emulsions also had the advantage that they could be washed.

In the wet collodion process, silver nitrate reacted with a halide salt ; potassium iodide, for example.

This resulted in a double replacement reaction.

The silver and iodine ions in solution reacted, forming silver iodide on the collodion film.

However, at the same time, potassium nitrate also formed, from the potassium ions in the iodide and the nitrate ions in the silver.

This salt could not be removed in the wet process.

However, with the emulsion process, it could be washed out after creation of the emulsion.