On Wed, 14 Feb 1996, Jack Thompson wrote:

> In the course of 20 years of visiting museums and observing their
> conservation efforts I have been to one (!) where a hygrothermograph was
> actually being callibrated.

When I worked at Boston National Historical Park (about 10 years ago), it
was part of my job to maintain and callibrate the recording
hygrothermographs. We used an aspirated psychrometer (a small fan draws
air over the bulbs) to overcome the limitations of a sling psychrometer.
It was not my impression that this was an unusual procedure for an
historic national park site. By the way, I usually did the callibration on
days we were closed or before we opened to the public. Just because you
haven't seen anyone callibrating those ubiquitous recording
hygrothermographs doesn't mean it isn't being done.  (I do agree that it
can be tricky to learn to use a sling psychrometer accurately.)

Susan Wageman
Grants Manager                    [log in to unmask]
The Tech Museum of Innovation     (408) 279-7178
145 West San Carlos Street        fax (408) 279-7149
San Jose, CA  95113  USA          http://www.thetech.org