Humidity Control

[Bob Anderson]

In reply to Bill Maxim's posting about RH:  You're right, Bill, that
raising the temperature of a volume of air will reduce the RH. But the
other way to reduce the RH is to remove water from that volume of air.
Air conditioning systems(not evaporative coolers) remove water from the
air. To that extent they lower the RH. But the first thing that happens
when air is brought inside from outside and cooled is a rise in RH.
 Here in Tucson we experience quite a difference between air
conditioning systems and evaporative coolers. The AC systems keep the RH
a lot lower if the RH outside is high enough. So you might conclude that
the AC system lowers the RH. But it is important to remember that
lowering the temperature of a volume of air will raise the RH.

As to what's going on outside our homes in the atmosphere, the weather
systems in the Summer can hold more water(absolutely) than the Winter
weather systems. In the Winter we have drier air, bring it inside, heat
it up, lover the RH. The opposite holds in the Summer. The air has a
higher water content, we bring it inside, cool it, and raise the RH.

To piggyback another issue - Jon Piesik's question as to whether a
Dampp-Chaser system will help the failing pinblock in a grand piano: NO,
it will not. The grand system is limited to the soundboard. In a
vertical piano it is possible for the DChaser to help out the pinblock.

I would issue a warning, though. The DChaser system is a preventive
measure. It should not be thought of as a way of reparing damage to a
piano. I have had some success with DChasers making vertical piano
tuning pins tighter and even(in one case, in a grand piano) adding
enough extra crown to the soundboard to move the bass strings far enough
away from the plate near the bridge to stop buzzing against it when they
were played. But don't ever count on results like this. Use the DChaser
before the piano develops problems.

Bob Anderson
Tucson, AZ