Re: Gum & the commercial ?
Yes--the British Journal of Photography from 1850's on--I'm now up to 1930 this week (it wasn't called the BJP in the beginning). But the chloral hydrate and glacial acetic acid were Herr Watzek's formula in the Weiner Photographische Blatter (whatever that might be). It is gelatine 40 grains, chloral hydrate 25 grains water 100 minims.(possibly chloral hydrate or acetic acid to allow cold dev of gelatin)I had forgotten about pH influence on "solubility" of gelatine, this calls for a few more days in the lab :-) Is there any best article or well referenced starting point for this subject? (overview & history of the praxis of "gum printing") -
What the heck is chloral hydrate anyway??? Ohhhh, for a chemistry degree....
I unfortunately don't read German; I have had several German books translated for me but there are many more on gum that you can get all this more techie stuff out of. Go into WorldCat or some library world catalog and google gum bichromate or gummidruck and German if you are so lucky to read it. They were prolific around the 1900's with gum books.
I have had a somehow simplified view that gum printing is gum arabicHalvor, I just shared the different ingredients in gum throughout history for interest--but it seems that no one uses the extra ingredients anymore.... Some may still have possibilities nowadays though--I was going to test one or two. But it seems that they were all vying for trying to duplicate Artigue paper, or guess its secret formula. Yes, it was a one coat paper, as were all the gum papers, so with tricolor or multiple exposures some of the other ingredients became either overkill or disproved as the "latest greatest thing".