Silica gel

In response to Vera Espinola's silica gel question:  the real
question should not be about silica gel, but about the needs of the
objects in the case.  In a reasonably controlled room, a well-sealed
case will buffer changes and produce RH levels in the middle of
those in the room.  If the objects need levels either higher or
lower than what occurs naturally, then condition silica gel can be
used to produce this.  Also, if the gallery environment is not
well-controlled and the objects need a steadier RH level than is
produced by the buffering capacity of the case, then silica gel will
boost the buffering capacity of the case.  In the first situation,
the s.g will need to be reconditioned periodically; in the second,
it will probably be possible not to recondition it.  But in both
situations, the actual behavior of the environment needs to be
monitored both before the objects are installed and after.  In
either situation (as well as when s.g. is not used), the materials
and construction of any case with RH-sensitive objects inside need
to be looked at seriously.

B. Appelbaum

                                  ***
                  Conservation DistList Instance 11:71
                 Distributed: Friday, February 20, 1998
                       Message Id: cdl-11-71-003
                                  ***