Great questions and answers!
First, about the board. It was bought a month ago, prior to which it had been stored in a shed, then upstairs in my shop.
I excavated the seat and it immediately cupped, the excavated side of the board going concave. I tried the sunlight trick, without any permanent effect. I then made a fork test (correct term?) on a scrap and the forks bent in and have stayed that way for a week now.
After I posted my first query here, I found this article: http://www.woodweb.com/knowledge_base/Conditioning_Relieving_those_stresses.html
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P>I screwed battans to the seat, figuring that if I wet only one side of the seat I would simply cup the board, without permanently effecting the tension-set. After heating my kiln up as high as it would go (140F), I put a soaking wet blanket against the convex side of the seat and left it in the kiln overnight.
Left it out of the kiln two days and just took the battans off a half hour ago. Seems to have worked. Need to do it again to one end where the screws popped loose, but assuming it doesn't move, I think it is a success.
Question: What effect does the heat have on the process? I know heat plasticizes lignin, but does that help with these cross-grain issues?
A somewhat unrelated question: Are there any sources for info on what happens to wood in a kiln that could make it seem brash and hard to work with hand tools?
Thanks for your help!
Elia