[pure-silver] Re: JandC Pro 100 and 620 film
- From: Ray Rogers <earthsoda@xxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Thu, 26 May 2005 02:42:26 -0700 (PDT)
--- Ryuji Suzuki <rs@xxxxxxxxxxxxxxx> wrote:
> Some of compounds that were very commonly used in
> early days of Verichrome Pan are made obsolete
during 1980s.
Could you be more specific?
Which compounds are you referring to?
What were they replaced with?
How do you know that they were actually incorporated
in VP?
--------
It is certainly true that kettle shape and all sorts
of incidentals make a difference... I have described
elsewhere the great importance of Quality Control in
emulsion making. That actually is a major part of the
formula... the specs which are to be maintained.
Formulas are constantly adjusted to maintain the
desired characteristics, when the results from the
standard materials and processes change.
As I understand it, The same product made from two
different sites, do not necessarily have the identical
formula. Each site adjusts their formulas according to
their need... and that might even relate to local
customer preference for all I know.
So while what you wrote...
So the exact formulation of film emulsions of the same
name inevitably had to change over time. In that sense
Verichrome Pan immediately before its discontinuation
is different from the original VP.
MIGHT be true, I wonder if you really know that they
WERE different?
Without definite (that is, someone's first hand)
knowledge, it is just speculation.
Please be clear when you speculate.
<(The effect of vessel size itself is
> obvious in my hands when I make 100ml emulsion or
> 500ml emulsion.
That is because 2 or more very important parameters is
thereby altered! Those emulsions are therefore
different, and unless those parameters are readjusted
to give you the results you were obtaining previously,
well, the results will be different.
< Unless I do something, 500ml emulsion has bigger
grain.
Yes probably, but are you speculating again or are you
actually measuring grain size?
Based on my reading, modern emulsion plants
> make a few hundred
> liters at a time.)
Even more.
Some Kodak Kettles stand elbow high and are about 1.5
meters in diameter... that should easily give 1000
liters, maybe more.
In 1987, Oriental began using 1400 Litre capacity
kettles.
> On the other hand, judging from the publications by
> Chinese emulsion
> scientists and engineers, their level of
> understanding of the art is
> far more than the days of Verichrome Pan.
They are
> capable of modern
> emulsions
They certainly are.
I think Chinese know how is often under
rated. While they may not be producing what they are
capable of, they are quite skill-full with the tools
they have.
> The incentives to use more modern technology are
> numerous. Modern ones give better photographic
properties and cost less.
Cost less? Yes but better photographic properties?
What Properties are you thinking about?
---------------
Ray
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