Re: Gelatine is also '' a '' gum but not Gum.

A more appropriate generic name than gum would be direct dichromate
colloid processes. This would included processes we commonly call
Gum, gloy, PVA, direct carbon, Fresson, Artigue, Hochheimer Gum,
Paper Noir Gomme, Tempera Print, Cassein, etc. and a bunch of others
I forget.

In general, although there are some important working differences,
they all work on the same basic principle, ie. exposure (and
hardening of the gelatin) is from top to bottom, with no transfer of
the image (as in carbon and carbro). Also, many of these processes
involve the use of more than one colloid, as was true of Fresson,
Artigue and the many commercial gum papers that were once produced.
You might mix gelatin with gum, or gelatin with fish glue, or fish
glue with rabbit glue, or cassein with gum arabic, and blah, blah,
blah for ever.

And each mixture would give a slight variation in terms of working
procedures and appearance, which would be, at least IMHO, a more
interesting and useful topic for discussion than what this discussion
has offered so far.

Sandy

>Ha, John, been there, done that.
>
>It was an old method to "speed" gum up. What it did was create stability in
>the highlights, in other words, lotsa staining. The more acid, the more
>staining. But I can imagine that back in the day when they were believing
>that gum didn't give halftones and it produced "soot and chalk" images, that
>it was a good enough technique, especially with the variability in
>negatives they might have had..
>
>I love those old gum recipes, additions of all sorts of stuff. I just had
>an old book translated for me from the German on the egg white gum print, a
>combo of the two. My translator has translated 4 such books now, 4 more to
>go. They are a HOOT, these old books.
>
>Do you think it is no longer a gum print, but an acetigum? A gumacete?
>Chris
>
>
>
>>Just to complicate the issue further I read in one of my old photographic
>>dictionaties that a very useful gum can be made by adding acetic acid to a
>>solution of gum arabic.
>>Have a nice Spring, yo all. John - Photographist - London.
Received on Tue Apr 4 09:55:45 2006