Hygrometer

[Ron Nossaman]

>Doesn't anyone use a good hygrometer? Do y'all just stick a board in the 
>oven until it is light brown and slightly crisp? Or can you make it pop up 
>at the proper time? Maybe one of those little pop-up buttons like on a 
>Butterball?
>
>Terry Farrell

How "good" is "good", and how critical is absolute accuracy to your purpose 
and process? No two pieces of wood are going to react quite the same to 
humidity changes, so your chosen material is every bit as much a detriment 
to "accuracy" as a cheap hygrometer. You can buy a decent sling 
psychrometer for something in the $80-$100 range and use it as a cross 
check and calibration device for your cheapie, for your own information and 
peace of mind. You can also use various saturated salts to calibrate. Try 
http://www.natmus.dk/cons/tp/satslt/satsalt.htm .

As I said, the most effective way around the need for absolute accuracy is 
to build soundboard assemblies that are more tolerant of minor 
irregularities. I dry panels down with a little space heater using the 
piano as my hot box. The panel lays on top of the rim, the heater goes 
underneath, and moving pads go over the top. My little +-2% hygrometer sits 
on top of the panel, under the pads. A couple of days later (depending on 
the season), when it's showing 30%RH, the panel's ready to work. The 
piano's probably a little smaller too, but that doesn't seem to be a 
problem. If I was running a high volume operation, I'd have more floor 
space and build a dedicated box, but I don't expect the basic system would 
be much more sophisticated than what I'm using now except for controlling 
the heat source with a humidistat - and not shrinking the piano too, of 
course. I'd prefer this, since the panel could "soak" a while longer than a 
couple of days and more nearly stabilize, but I haven't noted any problems 
from the rather crude and inelegant way I do it now.

But if you must have absolute accuracy, and that costs $40K, then $40K is 
what you need to spend.

Ron N