Hygrometer

[Greg Newell]

Ron,
         If one were to strive for and "for the sake of discussion" achieve 
that absolute accuracy how long could the board be expected to stay that 
way after it is removed from the "hot box" for working? If I took the board 
out and got a little side tracked and didn't get to gluing my perfectly 
formed ribs on until say an hour or two later ... am I too late? do i need 
to start the process of drying it down all over again?

Greg Newell


At 09:48 AM 8/30/2002, you wrote:

>>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

Greg Newell
mailto:gnewell@ameritech.net