[pure-silver] Re: PMK was Re: Tri X film versions and sizes
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Wed, 16 Feb 2005 17:15:04 -0800
----- Original Message -----
From: "Ryuji Suzuki" <rs@xxxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Wednesday, February 16, 2005 3:09 PM
Subject: [pure-silver] Re: PMK was Re: Tri X film versions
and sizes
> From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
> Subject: [pure-silver] Re: PMK was Re: Tri X film versions
> and sizes
> Date: Wed, 16 Feb 2005 14:51:22 -0800
>
>> In developers like Kodak D-7 the Metol appears to
>> function as a preservative for the Pyro. D-7 is an ABC
>> type
>> Pyro developer but it has much longer life.
>
> Intention and actual function may or may not be the same.
> By the time
> people came up with solid idea of what causes
> superadditivity and what
> are the favorable conditions for it to happen, no one
> cased about ABC
> and D-7 so I suspect that the description you are
> referring to is not
> necessarily up to date. (and probably won't be updated)
>
> It's a well known fact that developers containing
> hydroxybenzene alone
> have very short life but a bit of Metol decreases oxygen
> absorption.
>
> But all these are unrelated to the previous point of
> someone
> questioning superadditivity.
>
> --
> Ryuji Suzuki
> "Keep a good head and always carry a light camera."
What do you mean by "intension"? This is a developer
devised by Kodak labs and actually used for years. The
information on lifetime is not guess work. It may not be
superadditive but the presence of the Metol does make a
difference in the properties of the developer.
I was NOT suggesting that the two WERE superadditive in
D-7, only that Metol appears to have a preservative effect
on the Pyro.
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.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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