From: Judy Seigel (jseigel@panix.com)
Date: 11/18/02-11:20:55 PM Z
On Mon, 18 Nov 2002, Katharine Thayer wrote:
> Judy Seigel wrote:
> >
> > No, the "important point" is that a beginner doesn't know about "maximum
> > concentrations" or difference in solubility and takes the descriptions as
> > characteristic of the chemicals themselves....
CUT
> As to what beginners know, I would sort of expect beginners to know
> something about what a saturated solution is, since most gum printing
> instructions spell it out quite nicely (Livick being the lone exception
> of the sources on my shelves) and all recommend starting with a
> saturated solution of whatever dichromate is recommended or chosen.
Aside from the fact that most books don't know and don't say (examples to
follow), the question suggested that the asker didn't know, which is the
point at issue.
To not mention the difference in solubility, which is after all the MAJOR
difference, not only fails to answer a question about difference, it
misleads. Evem a non-beginner could conclude that there is -- as stated --
little difference. Period.
I would no more teach any level of gum without mention of this crucial
variable than without mentioning the variables of paper, size, pigment,
paint ingredients or gum arabics. In fact without the variables, gum is
just mix up 3 things, coat paper, expose & develop. That could fit on a
palm card.
Nor, alas, is ignorance about the various bichromates limited to
Livick, or even beginners...
Here is Scopick, the best known (ahem!) "authority" on gum in the planet:
QUOTE (p. 125)
Ammonium Dichromate... has a stronger sensitizing power
(approximately twice) and is more soluble than potassium. ....
Substitutions: for every 100 parts, substitute 117 parts of potassium or
sodium dichromate.
END OF QUOTE.
The paragraphs on sodium and potassium dichromate are similar:
For sodium dichromate Scopick says substitute for every 100 parts, equal
potassium or 85 parts ammonium.
Just Paul Anderson, who printed with 100% sodium dichromate solution,
would ruin that advice if it weren't already cuckoo.
Another book I happened to have out for another purpose is also absurd on
the topic. This is Jan Arnow's Handbook of Alternative Photographic
Processes.
After similar murk, she says of the 3 dichromates, "the one most sensitive
to light is ammonium dichromate....Sodium dichromate is slowest... " etc.
(If there is any meaning, it's clearly wrong. Sodium dichromate is either
100% or more soluble --and so would be "fastest.")
> ... but I've
> just learned that the PF kit has at some time, unbeknownst to me, been
> totally redone and now uses Livick's instructions rather than Anchell's,
> so I agree that anyone using that kit probably doesn't know anything
> about solutions, and from now on I will no longer be recommending the
> Photographer's Formulary kit.
That confirms, if such be needed, my all-points bulletin warning against
kits. It also bears out my idea that NEVER in the history of photography
has the "science" been as bad as it is in "alt" ... since about 1930.
There are I believe cultural and technical reasons, tho that's not this
message.
This message is to say that many of the non-beginners as well as beginners
on this list took Livick's workshop on the B&S site,and/or have the books
by Arnow, Scopick and others which they may have read. (Those books are
not alone by any means, just what was at hand). Maybe in fact that's why
people think gum is so difficult. They don't know the most basic basics.
Judy
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