U of S | Mailing List Archive | alt-photo-process-l | Re: 3 questions (one of them dumb)

Re: 3 questions (one of them dumb)

On Nov 16, 2008, at 9:13 PM, Ryuji Suzuki wrote:


From: Judy Seigel <jseigel@panix.com>
Subject: 3 questions (one of them dumb)
Date: Sun, 16 Nov 2008 23:56:38 -0500 (EST)


A friend, masterminding a class mixing vandyke brown
emulsion, finds that when the silver nitrate is dissolved in
the "distilled water" the solution turns somewhat milky.  I
recalled having had the same experience years ago,
ultimately discovering that the "distilled water" was
actually tap water, bottled as and labelled "distilled."

That's a very plausible story.


Friend said she'd been told there's a solution that tests
for "distilled" i(I have a note "Solenoid black from NZ" --
could that be it?) Any info or advice would be gratefully
received.

You would want to test for chlorination. Silver nitrate
solution is a pretty good test for it. There are some other
tests, such as ones used to test chlorination of swimming
pools.
I thought, also, Ryuji, that distilled water is that which has virtually no dissolved
minerals . . . what does chlorination have to do with distilled water? Does that
mean if you have chlorination you could add Hydrogen Peroxide and remove
the chlorine and then have distilled water?


So I looked up "chromogenic print" in the
two books I could find (two out of maybe 7 is a good rate
around here). The best definition was in Luis Nadeau's
"Encyclopedia," which explained that most "contemporary
color photographic materials belong to this category"
... also called "dye coupler prints," and "(improperly)
C-prints."

That is right. Dye coupler prints. Color prints made by the
RA-4 process or its equivalent are good examples of
chromogenic prints. Similarly, color films used today are
chromogenic (dye coupler materials).
Chromo means color, from the Greek and the Gen part basically means made, or formed.
A 'chromogenic' print is one where the color is formed. The Type-C print is indeed a misnomer
and was an invention by Kodak for a type of color paper. Therefore, not all color prints are C-Prints,
hence it being a misnomer. I think many people think the 'C' stands for Chromogenic but it doesn't.
While on the topic, other prints of color, like the Cibachrome (now Ilfochrome) are not Chromogenic.
They are dye-bleach, for the formed color being a different dye (Azo) is removed, not formed, during
the process.


3. What is glycin?  I know it isn't glycerine, more's the
pity, but it's not in Nadeau... There are of course some
photo chemistry books around here, now deeply buried in the
Morton Street Mississippi Delta. So, I thought, it can't
hurt to ask.

http://silvergrain.com/labs/Glycin

This is, for sure, much much more than I ever knew.
Jack F


--
Ryuji Suzuki
"Patriotism is the last refuge to which a scoundrel clings."
(Bob Dylan, Sweetheart Like You, 1983)