[pure-silver] Re: Here's one for the head scratchers
- From: "Dave Valvo" <dvalvo@xxxxxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sun, 16 Jan 2005 23:29:30 -0800
Some folklore for you.
In the early T grain days the T-grain emulsion systems, being large and
flat, were very pressure sensitive. So polymers were added to the emulsion
system to provide cushions for the T-grains. But the polymers absorbed
light and slowed the emulsion down so the T-grains were made bigger which
made them more pressure sensitive so more polymer was added which..........
----- Original Message -----
From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Sunday, January 16, 2005 5:16 PM
Subject: [pure-silver] Re: Here's one for the head scratchers
>
> ----- 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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