Great results, congratulations!
Originally Posted by R Shaffer
I don't know whether the two hardeners, formaldehyde and glyoxal, act at similar speed regarding emulsion hardening.
Maybe glyoxal takes much longer.
What about baking the plate right after the photographic exposure and prior to liquid processing? I remember having done baking (without adding any specific hardening agent) with a couple of gelatin based materials, like dichromated and ferric gelatin. They required a relatively long time of treatment - say, 45 - 60 minutes at 120°C. So this definitely complicates the whole process.
Regarding your developer I wasn't aware (anymore) it had such a high KBr concentration. As PE pointed out KBr also acts as a silver solvent. By the way there are colloidal developers that contain but KBr as the silver solvent. Moreover, in my reply to your post at the holography forum I forgot to mention that ammonia is both a silver solvent and a very strong alkali. So increasing/decreasing its amount makes it very tricky in respect to solvent/developing action.
So switching to another developer may be a better option I guess. There's an alternative to the GP-2 type of developers. I was involved with people from the Russian holography forum to set up a developer which replaces the ammonium thiocyante by sodium thiosulfate. I can't seem to find that link anymore. The whole thing was done with two stock solutions, one containing the thiosulfate only (I believe).