[pure-silver] Re: JandC Pro 100 and 620 film
- From: Ryuji Suzuki <rs@xxxxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Wed, 25 May 2005 17:40:16 -0400 (EDT)
From: Jim Brick <jim@xxxxxxxxx>
Subject: [pure-silver] Re: JandC Pro 100 and 620 film
Date: Wed, 25 May 2005 14:13:09 -0700
> Since Kodak owns a goodly sized chunk of Lucky Film (the largest
> Chinese film manufacturer,) there is a really good chance that this
> film that you speak of, IS Verichrome Pan.
Some of compounds that were very commonly used in early days of
Verichrome Pan are made obsolete during 1980s. 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.
Even if the film in question is following a certain generation of VP
formula, a factor such as change in the size and shape of vessel used
to mix the solutions can significantly change the photographic
characteristics of the emulsion. Manufacturers face this problem when
they take a formula from research to pilot to production plant. Then
they face the same problem again when the market demand changes or the
plant moves for some other reasons. So the actual emulsion formula may
be changing more frequently. (The effect of vessel size itself is
obvious in my hands when I make 100ml emulsion or 500ml
emulsion. Unless I do something, 500ml emulsion has bigger
grain. Based on my reading, modern emulsion plants make a few hundred
liters at a time.)
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 although they may not have accumulated know-hows of their
manufacturing and quality control yet. This is strikingly different
from eastern European factories, whose products largely depend on the
old German (or whoever's) technology.
The incentives to use more modern technology are numerous. Modern ones
give better photographic properties and cost less.
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