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Subject: Distorted microfiche

Distorted microfiche

From: Erich Kesse <erikess>
Date: Tuesday, August 17, 1993
It is difficult to diagnose a microfilm problem without seeing the film
or knowing something of its age and storage conditions, but I'd bet you
may be seeing acetate film deterioration.

Two basic groups of film have been used for microfiche production:
acetate (including diacetate and triacetate) and polyester.  Acetate
based film has grain and is subject to curl, where as polyester films do
(or should) not and tend not to curl.  (Curl, however, may also be a
result of (de)humidification: assuming the film is silver gelatin, the
gelatin may absorb moisture or loose moisture while the film base does
not.  Silver gelatin films are glossy on one side and dull on the other.
Other film emulsion types will not suffer this effect; other types will
be glossy on both sides.  If other emulsion types do suffer this effect
the problem is almost certainly film base deterioration.
(De)humidification effects might be associated with tackiness in cases
of humidification and cracked emulsions in case of dehumidification.)

Acetate based films are not particularly stable; they tend to loose
their plasticizers and shrink, shrivel and warp.  Polyester based films
tend to be much more stable.  Assuming your have a few disposable copies
of effected microfiche, you can determine base of film by simply trying
to tear them in two with pressure applied by finger nails and fingers.
Acetate based films will tear; polyester, generally will not.  If you do
not have disposable copies, the micropublisher may be able to supply
this information.

Corrective Measures:

1. If base deterioration: the effect can not be reversed.  It can be
   slowed by monitoring environmental conditions in compliance with ANSI
   standard, probably not possible in a patron-use collection.  For
   future acquisitions, purchase polyester based films whenever
   available.  For films already damaged, repurchase may be your only
   eventual option.

2. If climate conditions are unfavorable: placing a buffer between the
   fiche and the environment in the form of fiche envelopes per ANSI
   standards may be helpful ... and, would probably be helpful even if
   conditions are favorable.  But, this option is expensive.

Erich J. Kesse
Preservation Office
University of Florida Libraries
Fax: 904-392-7251

                  Conservation DistList Instance 7:21
                  Distributed: Friday, August 20, 1993
                        Message Id: cdl-7-21-003
Received on Tuesday, 17 August, 1993

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