---------- Forwarded message ----------
Date: Tue, 04 Feb 1997 17:29:50 -0500 (EST)
From: Jane Hedberg <jhedberg@WELLESLEY.EDU>
Subject: Microfilm

I am not an expert on microfilm and I strongly recommend that anyone with
questions about the nature of microfilm contact the Preservation Office at
UMI, 1-800-521-0600.  They are knowledgeable and helpful.  Having said
that, the simple, quick answer to the silver/vesicular question is:

Silver has the best image quality; what photographers call "snap".  It
should always be used for preservation master microfilming and any film
which requires a precise image.  However, it does scratch during use in
microform reader/printers, which can, over time, damage the quality of the
image.

Vesicular has an adequate image, although it appears less distinct next to
silver.  Scratches seem less obvious and damaging to image quality.   That,
coupled with the lower price, has led some people to prefer it for
commercially purchased "use" copies.  In my experience here at Wellesley
College, vesicular is fine for UMI-supplied microforms of periodicals and
holds up pretty well to our students' handling.

One last point, you should not mix silver and vesicular in closed storage.
If you are comtemplating switching from silver to vesicular, please contact
the UMI Preservation Office for their best advice with how to store your
microforms.

Hope that helps.  Jane

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              Jane Hedberg              jhedberg@wellesley.edu
              Serials Librarian and Preservation Administrator
                        Wellesley College Library
                        106 Central St.
                        Wellesley, MA 02181-8275
                     617-283-2103; fax 617-283-3690
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