[pure-silver] Re: AZO and Benzotriazole for anti-fogging
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Wed, 20 May 2009 15:59:34 -0700
----- Original Message -----
From: "Michael A. Smith and Paula Chamlee"
<michaelandpaula@xxxxxxxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Wednesday, May 20, 2009 3:53 PM
Subject: [pure-silver] Re: AZO and Benzotriazole for
anti-fogging
Hello Bogdan,
This is the first mention of Azo since I have
been back on this list, so I will chime in.
There will be no fogging on the Azo. If you have
read my articles on Azo (all at
http://www.michaleandpaula.com) you will see that
Azo that has been stored in hot conditions has
been perfect after thirty years. We now print on
Azo from the 1970s (and occasionally Azo from the
1940s). It is fine, except that it has lost a
little contrast.
I do not recommend Benzotriazole at all. It
causes an ugly blue color. use KBr instead. Also,
Dektol gives an unpleasant tone as well. Amidol
gives the finest results. The formula I recommend
is in my articles. Today, I add 50% more KBr, but
otherwise, the formula works best as printed.
Feel free to ask any questions.
Michael A. Smith
I think Azo is long lived partly because it is slow and
perhaps also because it contains something to stop the
ripening process from contining.
For some reason developers like Dektol/D-72 cause a
slightly olive color on some papers including Azo.
Benzotriazole tends toward a blue image. Amidol is quite
neutral.
The amount of Kbr given in most developer formulas is
the minimum for fog suppression and often considerably more
can be added.
The advantage of Benzotriazole over Kbr is that it
tends to reduce speed less for a given amount of fog
suppression although any anti-fogging agent is going to
reduce speed.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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