Use of desiccant in longterm storage

Does anyone have experience using Zorb-it to control humidity in
enclosures? We are considering using it, or another desiccant, like
silica gel, inside boxes of materials for long-term off-site
storage. Some of the boxes will contain paper materials, others will
contain audio, video, or data tapes, and still others will have CDs
or microfilm.

Since we will not be able to access these boxes for many months
(great physical distance), and thus will be unable to effectively
check/change conditions inside the boxes, I am concerned about using
silica gel canisters, which simply absorb moisture and may create
too dry an environment.

The advantage of Zorb-it, according to their website, is that it
achieves an equilibrium, by absorbing moisture when humidity rises
and releasing it when conditions are drier. It also never needs to
be "recharged". Silica gel, on the other hand, because it conditions
in one direction only, eventually reaches saturation where it will
no longer absorb moisture. So, in addition to wondering if it will
dry things too much, I also wonder if it will become ineffective
before we can get to it again (likely in 12 months time) to recharge
it.

The storage facility conditions for these boxes will range over a
year's time from 40-50% RH, and from 61-71 deg. F. The boxes will be
single-walled, lined with a polyethylene gusseted bag to (hopefully)
help maintain an inexpensive microclimate effect.

Any experiences with either of these, especially Zorb-it, would be
greatly appreciated.

Scott Campbell
Director of Archives
Avataric Ruchirasala of Adidam
707-928-1111


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                  Conservation DistList Instance 20:31
                Distributed: Saturday, December 9, 2006
                       Message Id: cdl-20-31-022
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