Quote Originally Posted by Hologram View Post
Great results, congratulations!

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 120C. 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).

I was thinking along the same lines with the hardening step, that the glyoxal is not really a 1 to 1 substitute for formalin. But in multiple searches I could not find any info for this application. Seems only us gummies use it for hardening our gelatin sizing. Sounds like a couple of tests are in order.

I like baking, I don't think my oven goes all the way down to 120deg. But maybe the toaster oven would. Need to get the OK from my wife before I start sticking stuff in the oven though :rolleyes:

I used the pyro-ammonia since it was (relatively) easy to mix up myself in small quantities, I only have small time windows to play with my little projects. Perhaps it would be better to try and raise the ph of the developer to slow down its activity?

I have the PF GP-2 developer as well, that I intend to use for another try. I just did not want to mix up a whole liter of developer for the first go as it will be a couple of weeks before I can get back to testing. But I like the idea of a comparable developer that uses regular hypo. I also saw some pyrocatecol developer formulas, I need to see how close they are to my pyro-cat HD, wouldn't that be cool.

Thanks, this helps.