Activated charcoal

Ian Loughheed inquired about the use of activated charcoal.  The
definite data that I have found that answers his questions is from
the instruction sheet written by 3M for their "Silver Protector
Strips" product, which is activated charcoal on paper.  The strips
protect on a ratio of one sq. inch of paper to 30 cubic inches of
container void. For further information on the product, contact

    Layton Marketing Group Inc.
    3584 Hoffman Rd. E.
    White Bear Lake MN 55110
    651-779-8000

The length of protection time depends on the permeability of the
storage or shipping container and the pollution level of the
surrounding atmosphere (the 3M product is intended to adsorb
hydrogen sulfide in particular).  As a rough guide as to duration,
they suggest the following time periods based on nature of the
environment:

    a) loosely sealed container (chipboard box):   6 mos.

    b) Moderately tight seal (sealed poly bags):  12 mos.

    c) tightly sealed (low permeable poly):       24 mos.

I would think that this information is applicable to the use of bulk
charcoal particles as well.  The main disadvantage of using charcoal
as a pollution adsorber is that it will start to off-gas the
pollutant once the adsorbing surfaces are completely occupied.  It
cannot be regenerated.  That is why there have been recent
developments with the use of zeolites, and zeolites in combination
with charcoal, in pollution adsorbent storage materials such as
matboard and even paints. Check the Conservation Resources Ltd.
catalog and contact them for information on the tests that they have
carried out.  I would think that the conservation scientists at the
GCI could also give you some data on the use of charcoal and other
adsorbents.  Good luck in your research,

Paul S. Storch
Objects Conservator
Daniels Objects Conservation Laboratory (DOCL)
B-109.1, Minnesota History Center
345 Kellogg Blvd West
St. Paul, MN  55102-1906
651-297-5774
Fax: 651-297-2967

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                  Conservation DistList Instance 12:51
                Distributed: Tuesday, December 15, 1998
                       Message Id: cdl-12-51-005
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