From: Judy Seigel (jseigel@panix.com)
Date: 05/23/01-09:01:23 PM Z
First, let's please put to rest this thing about hooves. The
occasional hoof might have "slipped" (no pun) into a gelatin batch,
but animal hooves are not a source for gelatin and are made of an
entirely different protein than the collagen protein needed for
gelatin.
In the early years, some of the uniqueness/usefulness of gelatin did
indeed derive from the sensitizing effects of very low levels of
certain unknown impurities (e.g., now known to be metal ions, nucleic
acids and sulfur compounds). However those "impurities found in Mr.
Eastman's gelatin" that Arni refers to were actually just Kodak's
wild-a** guess made at the time of a gelatin quality control disaster
that nearly destroyed the Kodak Company. While the story typically
alleges that the problematic batch of gelatin was derived from a herd
of cattle feeding on mustard plants, such a conclusion--if ever
made--was necessarily a pure (and improbable) speculation, since no
one could have any way of knowing the diet of the animals involved in
any batch. The necessary chemical analysis capabilities at that time
did not exist; also Kodak did not make its own gelatin then, nor
would any gelatin manufacturer ever likely to have knowledge about
the diet of the animals that provide his raw material (bones/hides).
All that is actually known is that Kodak was the victim of an
unusually "active" batch of gelatin that caused severe problems with
emulsion sensitivity. That issue alerted George Eastman to the need
for tight control of his raw materials, and eventually it led Kodak
into the business of making its own gelatin. For many decades Kodak
only used gelatin of its own making (in Rochester and Peabody,
Mass.). All that's changed since the 1980s.
Since those very early years, the photographic gelatin used in modern Ag
halide emulsions has become a relatively well-refined, carefully analyzed
and controlled material that relies on precise addition of known chemical
sensitizing compounds to produce the needed photographic responses (rather
than relying on impurities).
Arni is quite correct that the hardening issue is certainly not a
trivial problem nowadays, given our awareness of health hazards
involved with many protein crosslinking agents (e.g., formaldehyde
and others).
Phil
(retired from Kodak, but evidently not from gelatin)
--Phil Rose Rochester, NY mailto:pjrose@frontiernet.net - Turn off HTML mail features. Keep quoted material short. Use accurate subject lines. http://www.leben.com/lists for list instructions.
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