[pure-silver] Re: PMK was Re: Tri X film versions and sizes
- From: Ryuji Suzuki <rs@xxxxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Wed, 16 Feb 2005 20:29:04 -0500 (EST)
From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
Subject: [pure-silver] Re: PMK was Re: Tri X film versions and sizes
Date: Wed, 16 Feb 2005 17:15:04 -0800
> What do you mean by "intension"?
I meant intention.
> I was NOT suggesting that the two WERE superadditive in
> D-7, only that Metol appears to have a preservative effect
> on the Pyro.
But that's not the point of the previous post to which you responded.
> I am not sure when the idea of superadditivity was
> developed but it must have been pretty early on, maybe the
> late 1920's. It seems to be a very old idea. The effect
> might have been known and used well before a good
> explanation of it existed just as the pH rise of D-76 was
> known shortly after it was designed. Carlton and Crabtree
> did not know what caused it but were able to deal with it. I
> think you short change the knowledge of the past.
The early observation of superadditivity goes back to c. 1890. But
there was no agreement as to what was the mechanism of superadditivity
until late 1940s. More definite answer had to wait for 1970s.
Using empirical knowledge for engineering problems is different from
scientific understanding of what is going on in the actual development
process. The previous post to which you responded was concerned about
the latter.
Also, note the inconsistency between your statement about D-76 being
superadditive here, and your post a few days ago saying hydroquinone
in D-76 has no contribution.
--
Ryuji Suzuki
"Keep a good head and always carry a light camera."
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