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Subject: Hair bundles for hygrothermographs

Hair bundles for hygrothermographs

From: Helen McPherson <hmcpherson>
Date: Wednesday, September 25, 2002
We have a range of drum hygrothermographs ( thermohygrographs in our
part of the world), including battery and clockwork models, Nikkei,
Sato Sigma, Izuzu, Ogawa Seiki and Michromech. Depending on the
machine location, they run on 7 and 31 day cycles. The machines are
recalibrated using an electronic hygrometer, each time the charts
are changed. The hygrometer is recalibrated inhouse every 12 months.
We have a stand-alone data logger, but due to budget constraints,
are not in a position to purchase further units at the present time.
We also have a sling psychrometer, which is used on various

In the past, we have had the thermos serviced by local companies,
but some companies are discontinuing that practice. I'm seeking
information on the hair used for the humidity sensor; one of my
manuals says that it is "a bundle of specially treated human hair",
but it doesn't say what the hair is treated with. The DistList
archives has references to hair bundles, but I'm seeking more
information.  A local company said that the hair should be cleaned
weekly, by giving it a light misting with water. This struck me as
being counterproductive to what we want the machine to do, and also
somewhat hazardous in that the water would have to be localised so
that it didn't affect other parts of the machine. I'm assuming that
after any cleaning or replacement of hair bundles, the thermo would
be recalibrated.

My questions are:

    Should the hair bundles be cleaned, how frequently, and what
    implement/liquid should be used?

    How often should the hair bundles be replaced?

    Are there different hair bundles for different machines, or is
    it one-size-fits-all (i.e. cut your own to size)?

    Source of hair bundles? Cost?

    Can the hair bundles be fitted to a machine by a competent
    preservation technician, and are there any specific procedures
    to be followed to get the correct tension?

Thanks in advance for suggestions and advice,

Helen McPherson
Preservation Packaging Team Leader
Preservation and Storage Division
State Library of Victoria
328 Swanston Street
Melbourne 3000 Victoria  Australia
+61 3 8664 7372
Fax: +61 3 9639 6559

                  Conservation DistList Instance 16:23
               Distributed: Wednesday, September 25, 2002
                       Message Id: cdl-16-23-023
Received on Wednesday, 25 September, 2002

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