[pure-silver] Re: Here's one for the head scratchers
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sun, 16 Jan 2005 17:16:37 -0800
----- Original Message -----
From: "Ryuji Suzuki" <rs@xxxxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Sunday, January 16, 2005 3:21 PM
Subject: [pure-silver] Re: Here's one for the head
scratchers
> From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
> Subject: [pure-silver] Re: Here's one for the head
> scratchers
> Date: Sun, 16 Jan 2005 14:01:52 -0800
>
>> Modern emulsions contain additives for the purpose of
>> reducing or eliminating pressure effects.
>
> What kinds of compounds are you talking about?
>
> I add nothing to my emulsions for this purpose but I don't
> get
> pressure effects. Of course I handle my materials
> carefully, but even
> if I give some pressure with fingers and nails, the worst
> that happend
> to me is blotting of processing solution to the paper base
> with some
> paper stock, appearing darker while wet, or damage to the
> emulsion
> before getting any developed area due to pressure.
>
> A retired Kodak emulsion expert told me that some old
> products using
> halide conversion were so highly pressure sensitive and
> the technology
> was abandoned. This type of technology is also described
> in Keller,
> but the sentence is written in past tense, though it
> doesn't say it
> was abandoned. Some of my formulae use that technology,
> and they work
> very well in my hand. I don't know why. The chloride paper
> print on
> the pure-silver weblog (photolog) is made that way with
> 20% bromide in
> the shell after precipitating 100% chloride core.
>
> --
> Ryuji Suzuki
> "Keep a good head and always carry a light camera."
I don't remember anymore where I read this but it must
have been one of the standard references. pressure effects
are well known so there must be a fairly large body of
papers written about them or mentioning them. You have a
much better access to this stuff than I do and would also
probably understand a lot of the more advanced research
which is beyond me except in a very general way.
Since the understanding of latent image formation has
changed over the years its likely that the understanding of
pressure effects has also. I know this has been a problem
for certain printing papers in the past and some special
purpose emulsions. It is possible that some anti-foggants
may be effective. One reason for the inclusion of Potassium
Iodide in some X-Ray developers is to reduce the effects of
fogging from mechanical causes such as surface abrasion.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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