EMC and working time for soundboard panels

[Ron Nossaman]

> Does anyone know from their own experience what the approximate working time
> is for a soundboard panel before it starts to appreciably change its EMC.  I
> realize it depends on the RH and temperature, so let me be more specific.  I
> know that I can maintain a 6.2% EMC by simply keeping my shop at 30% RH and
> between 60 and 70 degrees F.  While I have no trouble keeping my
> conditioning box at those numbers, getting my shop below 40% and stable is
> difficult--though I can keep it around 45% relatively easily.  If I pull the
> panel out of its 30% RH box into a 45% RH room, approximately how much time
> do I have to work with it before it will move above 6.5%?  

At least a couple of hours, maybe half a day. This is why I 
made my MC gage, to get direct readings instead of trying to 
judge. Maybe I need to write up that Journal article I've been 
putting off.


>At 45% RH and
> those temperatures listed above, the EMC would be more like 8.5%.  I'm just
> trying to get a sense.  Also, approximately how much time is needed back in
> the box to return it to 6.2% (assume 70o).  

That depends on the temperature in the box. The higher the 
temperature, the shorter the cycle time. MC transfer rates are 
proportional. The higher the moisture differential between the 
wood and the environment (either direction), the faster the 
transfer rate.

Ron N