<HTML>In a message dated 8/30/2002 4:38:21 PM Pacific Daylight Time, gnewell@ameritech.net writes: <BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">Subj:Re: Hygrometer Date:8/30/2002 4:38:21 PM Pacific Daylight Time From:<A HREF="mailto:gnewell@ameritech.net">gnewell@ameritech.net</A> Reply-to:<A HREF="mailto:pianotech@ptg.org">pianotech@ptg.org</A> To:<A HREF="mailto:pianotech@ptg.org">pianotech@ptg.org</A> Sent from the Internet              Greg </BLOCKQUOTE>                     I know this question wasn't directed at me but let me share an answer with you.                In my setup I have a hot box I can store a few panels in. On the door is a window and behind it is the radio shack temp and R.H gauge. In side is a series of damp chasers and a small fan on the floor. On the outside of the door I have a chart the tracks E.M.C. in relationship to R.H. ie   90 degrees f. nets  5% emc in spruce. This is a chart out of I believe the governments wood book    Any way if I want to be sure the board is suffienctly dry in modestly humid weather I let it cook for three  days unless its been sitting in the shop at 30% or less anyway. The fan circulating helps of course to enenly dry all areas of the panel.      The same result will happen under a blanket with a space heater too. Nothing wrong with the way Ron does it and his other point about the rib set being the most critical factor should be pondered as much as this current question on emc.      If your shop is humid without controls you'll want to rib the panel in hour or so and don't answer the phone. If Rh is lower in the shop that's different. My feeling is it takes a couple hours for the spruce to take on insuffiecnt moisture to significantly change the outcome of your rib crowned project.      Remember the conditions which many soundboard were pressed up in the Piano factories on the East coast were archaic at best. The zero EMC in the winter and 80% with high temps in the summer. In your worst day in your shop you'll all do better than that.    It sounds like there is a search for parameters in this discussion which is important and when found will keep us from having undue  anxiety in the board making process.    Best____Dale Erwin <BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px"> Ron,         If I correctly understand what you are doing with your sophisticated :-) setup, you are looking for a change not necessarily a specific number from your meter. Correct? Do you feel that you can adequately state the moisture content of the wood from an instrument designed to measure the air simply because it is against the wood and trapped under a blanket? What would happen to the measurements if you introduced , say, a 6" air pocket around the hygrometer instead of having the blanket on top of the meter? Do you think that the readings would be different? the environment you create with the space heater under the piano is not necessarily the same environment above the board . Would you agree? If you measured the MC under and over the board they would surely be different, right? Could it be possible that some degree of instability is possible because of this? I know the board is relatively thin but without air circulating around the top could there be potential problems with uneven rates of contraction of wood fibers? Would this cause future problems with cracks or is this all semantics and nothing to worry about. Thanks for your indulgence of my random thoughts! Greg </BLOCKQUOTE> </HTML>