Your humidity is higher than 70-75%, based on how you describe the feel
of things. Items in the room probably are getting cool at night, and
then, the even more humid night air (cooler air holds less water)
condenses as water on the cooler surfaces. This liquid water creates
even higher humidity as it evaporates back into the air, as water vapor,
as the dew point increases. Your air may have been as measured, 70-75%
RH, at some point midday, but if you feel wetness at that humidity, this
is telling you a different story.
You can live with 70-75% RH for a good long time.
Fabrics that feel damp in 70-75% air, are far wetter than fabric at
equilibrium with that moisture content should feel. They are probably
wetter, and are evaporating off that "gained" moisture as the "dew
point" of their local room air allows. Use a recording hygrothermograph
if you can find one, you can even use old charts if you can use a
different color of ink; the digital version would be ideal. These will
tell you the real story at night, in the morning and midday.
The most unstable materials are those that have already had contact with
mold in the past. [Big help, right?] Spores are dormant for a long
time waiting for the right pH, RH and lack-of-air-movement conditions.
Any of the materials you mentioned could be the first to go, based on
the degree of mold present in/on them. Closed books are slow to follow
moisture changes, even on the way back down again.
The solution is to put "devices" in "the room" that will condense water
from the air before it can condense on cool surfaces. When water
condenses on a surface, it is depositing moisture in the room more
permanently, rather than just being in the air, which can be transient.
These "devices" are dehumidifiers or window air conditioners. Install
as many as you an manage, with the windows closed. OK, if you're in the
area of the floods then you have problems. The next less effective
solution is to keep the air moving, with the windows open. If you are
getting condensation, then keep the air "moving" all night as well.
This means you will need active guards watching everything.
No good answers, sorry. You have a difficult situation, at a difficult
time. Its best to be vigilant, you'll smell mold before you can see it.
Tim Vitale
Paper, Photographs &
Electronic Media Conservator
Film Migration to Digital Format
Digital Imaging & Facsimiles
Preservation & Imaging Consulting
Preservation Associates
1500 Park Avenue
Suite 132
Emeryville, CA 94608
510-594-8277
510-594-8799 fax
=========================================================
Important Subscriber Information:
The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed information about the listserv commands by sending a one line e-mail message to [log in to unmask] . The body of the message should read "help" (without the quotes).
If you decide to leave Museum-L, please send a one line e-mail message to [log in to unmask] . The body of the message should read "Signoff Museum-L" (without the quotes).
|