Re: Gum & the commercial ?
On 11/3/06 11:43 PM, "Christina Z. Anderson" <zphoto@montana.net> wrote: > Halvor said: >>> (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") - > > 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). Was afraid of that answer :-) The whole collection is in the library, but have a feeling if I first sit down to read that I wont leave in a year or so... Or wont get anything done.. > 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. > > What the heck is chloral hydrate anyway??? Ohhhh, for a chemistry degree.... > Apparently chloral hydrate is an antidepressant or hypnotic drug, may be something a gum printer would keep around :D ... But if I should make one guess here it sounds like Hydrochloric acid or HCl which would do something very similar as acetic acid in this connection, in my experience... Others may know. > 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. > Unfortunately I was given the choice between learning German or hunting in school... Pretty idiotic... Can however guess my way through it.. Will look. >> I have had a somehow simplified view that gum printing is gum arabic >> punctum, but obviously the physical method seems more important, or >> defining, than the materials. Despite the variety of names or >> terminology. >> I recognise some of what have been mentioned here, but that is all from >> various introductions for different subjects. >>> These commercial "gum" papers must have been intended to use as single >> layered then (?).. (Interesting, either better recipes or different ideas >> of >> "image quality"). >> Halvor > > Halvor, 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". > Chris > > More later :-)
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