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

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