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Subject: Liquid-gate printing

Liquid-gate printing

From: Barbara Brown <bbrown>
Date: Thursday, May 30, 1991
This is in response to Bob Kosovsky's query re. the possibility of
printing glass plate negatives using the liquid-gate technique. That
is a process primarily used with motion picture film. I'm not sure about
using it with still film, particularly with glass plate negatives. If
there is any instability, or damage, existing in the emulsion layer
(whether gelatin or collodion, a point I'll get back to in a moment)
then there is the possibility that further separation from the glass
support could occur.  


Re. the emulsion layer. Some confusion about collodion and nitrate was
indicated in Bob's letter. While both are nitrated cellulose esters, the
degree of nitration is somewhat different (Doug Nishimura could explain
all of this really well. We were discussing it over the phone the other
day.) Another point is that the collodion is the EMULSION layer on the
wet-plate negatives.  It is very, very thin, particularly in comparison
to the cellulose nitrate layer which serves as the SUPPORT/BASE layer to
what are known as nitrate (nitrate base) negatives. So the reference to
'glass plate negatives, some nitrate, is a bit misleading.  Nitrate
negatives are those on a cellulose nitrate base. Glass plate negatives,
as the name implies, are on a glass support or base.  The emulsion can
be gelatin(e), often referred to as gelatin dry-plate or dry-plate
negative (since this process enabled the photographer to work with a
dry, ready-made plate to produce a negative), as opposed to the
wet-plate collodion negatives, in which the photographer had to coat the
glass plate with th emulsion, expose it and develop it within minutes --
while the emulsion was still wet -- in order to produce a negative.
(This is rambling. I probably need an editor).  To try to sum up a bit,
here: while collodion and cellulose nitrate are very similar on the
chemical, molecular level, their function and physical characteristics
in these two types of photographic materials are somewhat different.
Wet-plate collodion negatives don't have quite the same deterioration
and preservation problems that nitrate-base negatives do.  This probably
isn't the sort of response that Bob was looking for, but I hope that
some of this will be helpful.

Check with Doug (@IPI) for further clarification on the chemistry.  Some
names of people that Bob might want to contact re. copying and
duplicating glass plate negatives are listed below (sorry that they
aren't on a computer network, or if so, I don't have an email address):

    Steve Puglia
    Nat'l. Archives in D.C.
    (202) 501-5370

    Michael Hager
    Rochester, NY
    (716) 442-7343

    Connie McCabe
    Washington, DC
    (202) 546-8631

    Doug Munson
    Chicago Albumen Works
    Housatonic, MA
    (413) 274-6901

Hope this will be helpful -   Best regards,

Barbara   (bbrown@utxvm)

                   Conservation DistList Instance 5:3
                  Distributed: Saturday, July 1, 1991
                        Message Id: cdl-5-3-003
Received on Thursday, 30 May, 1991

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