[R Shaffer]

I assume you mean pyro + ammonia. Yes, since ammonia is an AgX solvent that would be a colloidal (or solution-physical) developer. The problem involved with is ammonia evaporation, which makes the solvent action of this developer very unreliable.

Yes, I was referring to the Lumeire Pyrogallol-Ammonia developer. I could not decide which developer would be better, so I ordered both the GP-2 premix and the pyrogallic acid from PF so I could try both. Would a small covered tray help reduce evaporation?

I had never heard of solution-physical development prior to researching this, pretty fascinating.

Have you tried using glyoxal for hardening holographic plates? That is the hardener I have on hand & was planning to use. PF does sell the 37% formaldehyde solution, but I am going to try an avoid it.

I now have the plates & chemicals on the way to try this experiment out. I'll be sending half the plates on to Chris ( holmburgers ) as he is my 'partner in crime' on this. I am about half way through fabricating a plate holder with large black space behind the plate and should have it finished today.