At 10:28 AM 4/15/2005 -0400, you wrote:
><Believe the problem is caused by off-gassing of the glue that holds the
>film to the cards.>
>It can also be caused by off-gasing of the sulphuric content of the card
>itself.  Many older aperture cards were not sulpher-free or acid-free
>stock.


And another common cause is the mixing of diazo duplicate cards with silver
masters.  This typically results in a bad case of redox, which appears as
reddish-rust colored spots on the surface of the film and eats away at the
emulsion. And the only cure for this is to generate replacement images of
the affected cards and periodically review the collection to see if other
cards are affected as time goes along, and continue to replace them.

Bill is right that if these truly are "archival quality" images that have a
permanent retention period assigned to them and you want to retain them for
their historic, intrinsic or enduring value, the best bet is to make a set
of images that is stored as roll film in appropriate environmental
conditions and is supported by an independent index, and when accessed is
handled with the utmost of care and exposed to light for minimal amounts of
time, then returned to it's protected storage environment.

I've never seen a case where the adhesive has caused problems, and the
cards themselves (at least those produced and used post 1970s) were
typically not a source/cause of damage.  Most of the cases I've seen have
involved "human error", such as the mixing of diazo/silver film, use of
rubber bands to bundle bunches of film, storing cards in cardboard boxes,
use of improper materials as dividers and out cards, wrapping groups of
cards in improper paper/material for sorting, etc.

Larry

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