[pure-silver] Re: PMK was Re: Tri X film versions and sizes
- From: "Koch, Gerald" <gkoch02@xxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Thu, 17 Feb 2005 12:41:04 -0500
I have read a lot of the early literature (ca 1900 ->) and there is
mention of the addition of Metol to improve shadow detail. I do not
remember any mention of improved storage capability of working
solutions. However, this may be because pyro developers of the time
were discarded after use and people were not interested in preservation.
Jerry
-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx
[mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Richard Knoppow
Sent: Wednesday, February 16, 2005 5:51 PM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: PMK was Re: Tri X film versions and sizes
----- Original Message -----=20
From: "Ryuji Suzuki" <rs@xxxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Wednesday, February 16, 2005 2:20 PM
Subject: [pure-silver] Re: PMK was Re: Tri X film versions=20
and sizes
> From: "Koch, Gerald" <gkoch02@xxxxxxxxxx>
> Subject: [pure-silver] Re: PMK was Re: Tri X film versions
> and sizes
> Date: Wed, 16 Feb 2005 15:52:26 -0500
>
>> Even so the superadditivity ratio of Metol to
>> hydroquinone is around 1:3 or 1:4 and I would suspect
>> that it would be
>> in the same range for pyro.
>
> What's your definition of superadditive and "superadditive
> ratio?"
>
>> In PMK the ratio is 1:20 which does not appear to be
>> optimum.
>
> Does that make it non-superadditive?
>
>> Metol has traditionally been added in small amounts to
>> pyro
>> developers to improve shadow detail and gradation. Any=20
>> synergy
>> between Metol and pyro in PMK is a lagniappe.
>
> Does that make metol-pyrogallol non-superadditive?
>
> --
> Ryuji Suzuki
> "Keep a good head and always carry a light camera."
>
In developers like Kodak D-7 the Metol appears to=20
function as a preservative for the Pyro. D-7 is an ABC type=20
Pyro developer but it has much longer life. Kodak states=20
that in deep tanks it will last several weeks where ABC Pyro=20
like Kodak D-1 last only a few hours. From the limited=20
information given the two appear to be similar in activity=20
(development time). I think one would have to make=20
sensitometric tests to see if the Metol had any effect on=20
curve shape. The formulas are a bit long to copy them here=20
and are readily available.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx=20
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