OK - I responded to Clara off-list, but will accede to your
request. Toby Raphael's in-house NPS monograph _Conservation
Guidelines: Design and Fabrication of Exhibits_, Harpers Ferry
Center [1991] says (in "Technical Supplement No. 6, 'Standardized Silica
Gel Containers for Humidity Controlled Cases'"), "Estimated gel
quantity per cubic foot of case under standard conditions - 1/3
lb. of gel per cubic foot; 9 lbs. gel per cubic yard." My guess
is that "standard conditions" might means such factors as
reasonable T/RH in the surrounding environment. Additionally,
May Cassar's _Environmental Management: Guidelines for Museums
and Galleries_, London and New York: Routledge [1995] at p. 115
says in the box "Calculating the quality [sic] of silica gel
The empirically determined quantity [sic] of silica gel
required to buffer ambient RH is 20 kilograms per cubic metre
of display case volume. The effectiveness and duration of a
microclimate using a buffer material are determined by a number
of factors brought together in the formula: T=4 (M x B)/N days,
where T is the half-life of the case, M is the specific
moisture reservoir per cubic metre of case volume, and N is the
number of air changes per day."
As they used to remark about Junior Samples on the old TV
program _Hee Haw_, "If it was easy, anybody could do it."
According to Hank Burchard:
>
> If anyone responds to the request below, please do so on the list. I also
> need this information, and have not yet found a reliable source. Thanx.
>
> Hank Burchard * <[log in to unmask]> * Washington DC
>
>
> On Mon, 26 Aug 1996, Clara Margaret Deck wrote:
>
> > Subject: info request to post
> >
> >
> > Silica Gel Information requested.
> > I would like to hear from anyone who has worked with silica gel as a
> > buffering agent for sealed exhibit cases. More specifically, I would like
> > to know what ratio of silica gel-to- case volume has proven effective in
> > maintaining a reasonable RH range over time (say, three months).
> > The Canadian Conservation Institute recommends 20kg/meter cubed (a lot!).
> > I have cases with volumes ranging from 25 to 75 square feet, so I would
> > like to know if we can use less than this CCI recommendation, but still
> > buffer the RH effectively. Any ideas?
> > I am not a member of this list, (Jan Turner is our Institutonal member).
> > You are welcome to respond to me personally at
> > [log in to unmask]
> > Clara Deck,  Henry Ford Museum & Greenfield Village, Dearborn MI, 48121
>