Saturated salt solutions to control humidity

Oliver Tietze <oliver.tietze [at] gmx__net> writes

>A small church near Leipzig has got an altarpiece from 1520. It is
>in very bad condition due to the rapidly changing climate during the
>service. In order to prevent more damage a showcase has to be built.
>The RH in the church in winter is around 60% and the temperature
>around 2 deg. C, rising up to 15 deg. C over 12 hours, and slowly
>decreasing over 2 day after the service and up to 22 deg. C in
>Summer.
>
>Now I am looking for a buffer material for the showcase. A saturated
>solution of calcium nitrate could be it. ...

I offer these observations: Attention to the size, construction and
sealing of the showcase is as important (probably more important)
than the choice of humidity buffer. The wooden artefact itself will
provide some buffering, and there are a number of materials and
devices that can be used to augment this (appropriate silica gels,
saturated salts, active microclimate generators, etc.). The showcase
should be designed with the chosen buffering method in mind by
providing an appropriate compartment and access. The showcase will
be your first line of defence, as well as your greatest expense.

Further to this, the maintenance of the showcase and availability of
a caretaker to do this maintenance must be taken into account.
Maintenance will involve logging the environment, modifying or
replacing the humidity buffer, cleaning the showcase surfaces, and
related tasks. Should the calcium nitrate be considered too
difficult to handle by a volunteer working for the church, this
might be a reason to avoid its use.

Jerry Shiner
Keepsafe Microclimate Systems
800-683-4696


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                  Conservation DistList Instance 25:15
                Distributed: Tuesday, September 20, 2011
                       Message Id: cdl-25-15-005
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