[CAUT] Reading low humidity (was seasonal SB failure)

[Ron Nossaman]

> "Wood with very low EMC will absorb ambient high RH very
> quickly. It's slower to dry out, and it takes higher temps and airflow to
> speed that process (read institutional conditions <g>). I can measure RH
> easier than EMC, and RH is good at predicting what will happen in the near
> and long term future."
> 
>         I gain from this that wood reacts very quickly on the intake and 
> very slowly on the release. 

Not so. I've seen it assumed a lot of times, but have never 
been able to find documentation to that effect from even a 
minimally authoritative source. Both absorption and release of 
moisture in wood is proportional to the difference between 
wood MC and atmospheric RH%.

Even so, keeping track of RH% readings is a very good 
practical method of anticipating what the instruments' 
reactions will be with the resulting MC levels, which are 
lagging somewhat behind the RH% changes.

Ron N