I'm certainly far from clear on the physics involved, but
Originally Posted by holmburgers
Your recording in the film emulsion an interference pattern that occurs when light is reflected, the wave going out messes up the wave coming in. And if you have an emulsion with a fine enough grain, the interference pattern can be recorded. When you reverse the light reflection in the exposed & developed plate, it alters the light wave lengths to those you recorded and you see color . The paper you sent me has a much better description of what is happening.
The mercury acts as a mirror and so does the air-film with black space. Since the object, if you will, that we are recording is millionths of a millimeter, the gap between the mirror & emulsion would need to be incredibly small. The mercury mirror does move the location in the emulsion where the pattern is recorded further in. I don't know if this makes it easier to record or less sensitive to shrinkage & expansion.
The fogging I was referring to is due to the very small particle size in the emulsion. It can fog with-out light, but I don't know if it is a chemical fogging or something else. It can be cured.