From: Katharine Thayer (kthayer@pacifier.com)
Date: 11/09/01-04:26:04 AM Z
Richard Sullivan wrote:
>
> I've just posted the complete Zimmerman Gum process article from Photo
> Miniature October 1910. Go to:
>
> http://www.bostick-sullivan.com and look on the index page in the upper
> right corner under processes and you will find the link.
>>>>>>>>>>
>
> The topic is interesting in that there may be hints as to how enlarging
> speed gum is achieved by the Fresson's. I have a theory!
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Hi Dick,
What's your theory?
It took some doing, but I did read this article all the way through.
Does what you see as a hint for achieving enlarging speed have to do
with the unusually low (like 1:6) gum:sensitizer ratio he recommends? If
so I am inclined to doubt this is the answer, since while it's true that
increasing sensitizer relative to gum does increase speed, it also
decreases contrast. In my experience, even a change from 1:1 to 1:2,
given the same gum-pigment mix, is accompanied by a marked decrease in
contrast. So... show me some pictures. (The smudges accompanying the
article, of course, can't be taken as evidence one way or another, but
look hardly promising just the same.) Better yet, try this with an
enlarger and show us what you get. I'll be the first to cheer if it
works, but I'm skeptical...
I like his method for keeping a saturated solution of dichromate: put
the whole pound of dry dichromate into a pint bottle, and just keep
topping it off with water. Why bother with measuring?
His discussion of color printing seems surprisingly primitive, given
that the practice of using filters to make color separations goes back
several decades before his writing, although I'm not sure exactly when
those ideas were first applied to gum printing. Seems like at least by
1900, but no doubt someone has the exact history at hand.
Katharine Thayer
This archive was generated by hypermail 2b30 : 12/10/01-11:12:21 AM Z CST