Passive environmental control

Lynn Campbell <lynn.campbell [at] ccc__govt__nz> writes

>Can anyone suggest any passive systems that could help a heritage
>building that does not have power.  The building is close to the sea
>and has a large garden surrounding it. The displays are in glass
>cases and they are considering the use of silica gel as one method
>but would be interested in any other procedures that could help to
>protect their collections of archaeological and social history

With your NZ weather changing 4 times a day it might be hard for a
passive system to cope with that, as most of them depend on slow
physical actions. As your house is unpowered you need to put in the
power by yourselves, e.g. a lot of work in measuring, controlling
and reacting which is all in all quite an effort and goes along with
changes in your habits for all employees.

Silica gels and such can only compensate moisture levels at slow
rates and only if you keep the air changes per hour at a minimum. I
don't know your objects and displays, how airtight they are and
their setup regarding the silica gels deployment in the display, so
there are a lot of variables to take in account. Basically the
silica gels work fine as long as the room itself is kept quite
stable regarding temperature (also taking the lighting in the
displays into account) and relative humidity. Without power this
task is up to your personnel, if you are not up to change your
building in its structure as in making it a "passive house".

A thing I just recently learnt from Marcus Herdin (Preventive
Conservator at the Bavarian National Museum in Munich, Germany) is,
regardless what you do, you need to measure in your displays, as any
passive system can, in combination with other materials like a huge
mass of wood or paper, have a totally different effect than you wish
for. Some effects are so complex we cannot explain them yet, so
measuring and controlling are the only instruments we have.

Sorry for not giving you any good hints or alternatives as I don't
know any. You might want to talk to an engineer who has specialized
in climate control and is experienced in dealing with museums or you
need to take your time and run long term tests with different setups
of displays.

Alex Grillparzer
Student at Chair in Restoration, Technology of Arts and Science of
Conservation (Prof. Emmerling)
Technical University Munich
Germany


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                  Conservation DistList Instance 25:8
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