Re: POP process

From: Loris Medici <loris_medici@mynet.com>
Subject: Re: POP process
Date: Mon, 08 Nov 2004 20:37:15 +0200

> I don't know about POP but before I started to tone Vandykes in
> gold, I can say that I never experienced any image fading during
> fixation of untoned images (or my observation talent is very
> poor)... and I was using Christopher James' recommendation of fixing
> in 2% anhydrous sodium thiosulfate for not more than 1 minute - do
> you think this is far from being enough? (FWIW, please note that I
> always develop my Vandykes in 2% citric acid - I use plain water
> only for the final wash after toning/fixing).

I don't have a close working knowledge of Van Dyke process but I think
the difference you mentioned comes from differences in the size of
individual particles of metallic silver. Those image forming silver
in printing out process is really tiny. (In developing out process,
those tiny silver is chemically amplified several billion times to
make grains that you can only see in a decent microscope... not those
you see in grain focusers.)

From: Loris Medici <loris_medici@mynet.com>
Subject: Re: POP process
Date: Mon, 08 Nov 2004 23:42:14 +0200

> Richard, thanks for clarification. Having said "...KRST is not
> hazardous unless you drink it..." can you please explain my
> experience below?

I'm not Richard but that statement is something I would definitely not
say. I would even avoid or at least minimize skin contact with working
solution.

> I tried to smell KRST once and it made me kind of dizzy and stunned
> for a brief time - I quit immediately to smell chemicals after that
> experience. What would have caused this phenomenon?

Safety documents like MSDS and label warnings use terminology that is
specifically defined. Toxic, irritant, corrosive, flammable, etc. For
anyone who works with lab chemicals, it's important to know that they
mean different things and they have different ranges of possible
consequences. People on the internet (including those on mailing
lists) often blur the distinction to use different terms
interchangeably, which confuses others, but at the end, it is your
safety.

Anyway, as far as I know, ingredients of KRST are not likely to cause
acute symptom you described. Selenium is toxic but it does not cause
symptom that fast. (Note that I'm not saying that makes selenium less
toxic or anything.) My best guess of what you experienced is mediated
by irritation of your respiratory tract. Allergy (to food, pets, etc.)
can cause similar things although no toxic chemical is involved.

--
Ryuji Suzuki
"You have to realize that junk is not the problem in and of itself.
Junk is the symptom, not the problem."
(Bob Dylan 1971; source: No Direction Home by Robert Shelton)