Quote Originally Posted by Photo Engineer View Post
I have been thinking about the use of Citric Acid. This treatment might be harmful. IDK, but emulsions for the most part are at a neutral pH, say around 5.5 - 6.5. Citric Acid could begin to degrade the gelatin. Urea might be better for swelling the gelatin, if that is what you want. For an adhesive, Sorbitol, Glycerin, and other similar chemicals would probably be preferred.
I agree that citric acid may attack a not well hardened gelatin layer. But in my experience (limited to holographic/Lippmann emulsions only) urea is far more aggressive than citric acid.

Generally speaking, I guess better than doing post-swelling would be to have a more "conservative" approach:
- pre-harden the layer prior to processing;
- use a well-balanced colloidal developer (excess of thiocyanate results in loss of silver halide, producing a wavelength shift);
- dry the layer in ethanol or isopropanol.

Quote Originally Posted by Photo Engineer View Post
The Schlieren observed is not Nebel, but streaks could be caused by fog and thus be stated that way in the original text as a description of fog (Nebel).
Right. Moreover, again according to Neuhauss, removing all the mercury from the emulsion after exposure seems to have been a messy business.