Catherine,

One of the best resouces out there is the CD that has been produced by
the conservation staff at the NPS's Harper's Ferry Center on
Conservation Exhibition Guidelines. Here is the URL for that:

http://www.nps.gov/hfc/products/cons/ex-con.htm

The amount of silica gel required can vary depending on the case and
tray design and how air tight the case is. You also need to be
conscious that although archaeological metals benefit from the lowest
humidity possible if the cases contain mixed media then you will have
to compromise and set your target RH to the most sensitive and
reactive material in the case (e.g. wood, leather, ivory, etc.)

Also be aware that you are after an equilibrium and not an absolute
number. The silica gel will reach a point where it stabilizes with all
of the other materials in the case and environment (wood and textiles
and paper materials all have their ambient moisture content and can
wick moisture in from the outside just as well as the gradual
infiltration of air).

In Thompson's, "The Museum Environment" (1986, Butterworh-Heinemann,
Ltd.) pps. 232 -236, he discusses controlling RH in closed exhibition
cases and has a formula for doing so. His general recommendation for
well-built cases is 20 kg. silica gel per cubic meter of case volume.
There have been many improvements in both case construction and silica
gel products since Thompson's work, so there are more choices these
days.

I would recommend that you contact Emily Williams, the archaeological
conservator at Colonial Williamsburg. Emily has years of experience in
monitoring and maintaining the silica bag dessicant system at the
Winthrop Rockefeller Archaeological Museum at Carter's Grove. You can
call the general Colonial Williamsburg phone (757-229-1000) and ask
for her extention. Just tell her I referred you.

You also might want to talk to my old friend and colleague, Bly
Straube, curator of the APVA Jamestown Re-Discovery Project at
Jamestown Island. I know that they have been planning, in association
with the NPS -Colonial National Historic Park, for a joint exhibit of
artifacts for the 2007 anniversary extravaganza - so this topic may
have already come up in relation to that. (Tell Bly I said Hi!)

It is also a huge benefit to pack metal archeological finds with
dessicants as they come out of the field, since they can experience
very aggressive corrosion once removed from their more stable burial
environment. There is an excellent publication, "A Conservation Field
Guide for Archaeologists" by Catherine Sease, UCLA Press, that goes
over several ways of preserving artifacts before they can be
professionally treated by conservators.

Warmest Wishes for the New Year,
Dave

David Harvey
Conservator
Los Angeles, California  USA


On 1/3/06, Catherine Dean <[log in to unmask]> wrote:
>
> Can any of the conservators out there give me a rough estimate of how much
> silica gel is recommended per cubic foot for museum cases containing
> archaeological metal artifacts?
>
> Many Thanks,
> Catherine Dean
>
> Catherine E. Dean
> Curator of Collections
> APVA--Preservation Virginia
> 204 West Franklin Street
> Richmond, VA 23220-5012
> 804-648-1889
> [log in to unmask]
> =========================================================
> Important Subscriber Information:
>
> The Museum-L FAQ file is located at
> http://www.finalchapter.com/museum-l-faq/ . You may obtain
> detailed information about the listserv commands by sending a one line
> e-mail message to [log in to unmask] . The body of the message
> should read "help" (without the quotes).
>
> If you decide to leave Museum-L, please send a one line e-mail message to
> [log in to unmask] . The body of the message should read "Signoff
> Museum-L" (without the quotes).
>
>

=========================================================
Important Subscriber Information:

The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed information about the listserv commands by sending a one line e-mail message to [log in to unmask] . The body of the message should read "help" (without the quotes).

If you decide to leave Museum-L, please send a one line e-mail message to [log in to unmask] . The body of the message should read "Signoff Museum-L" (without the quotes).