I just bought, what appeared, pretty good walnut and oak – 1 inch boards. The MC was about 13% when measured in the lumberyard. Bare in mind that the working MC in Ireland is about 10/11%. I got the yard to re-saw the boards to half inch with the intention of getting them to the shop immediately, stickered, clamped and allowed to stabilize for a while before working with them. As soon as it was cut it began to warp and cup like crazy. I got it home and the oak was splitting before my eyes. I took a moisture reading on the cut face and it came in at 3 to 4%. Is this possible? Has the lumber yard left it too long in a kiln? With even the slightest pressure the boards cracked. I’ve begun to wet the cut face down and some flexibility is returning. What’s the correct approach in this instance? All thoughts would be appreciated.
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The only way the inside of the lumber could be that dry is for the kiln to have driven it that low. Then the outer shell must have equilibrated with the atmosphere, gaining moisture. And it must have done that in a pretty uniform way, with both sides absorbing moisture at the same rate, as I assume the boards were flat when you bought them. A reverse case hardened situation.
Because they were flat, they should return to that condition, or very close to it when they re-establish Equilibrium Moisture Content across the thickness of the re-sawn boards. Keep them weighted and allow air circulation to both sides of the boards. It's going to be several months before they settle down.
Rich
Thank you very much for that Rich. I think your diagnosis regarding the kiln drying is spot on. It must be criminal for a yard to do that.I'm going to take this as a little science project. After I dampened (liberally) the cut side of the board yesterday the MC read (naturally) about 30-35%. I had no stickers ready so I clamped cardboard between them to soak the excess moisture and arranged the boards alternately to cancel out the warping/cupping etc.I went back today with my stickers and the cut face/dry faces read 19% MC and no difference to the opposing face - 13%ish. The walnut has regained its flat shape completely. The white oak is putting up a bit of a fight though.I accept it will take a number of months for them to be usable - I've already begun sourcing more wood from a different yard - but I know I'll have them out again in a week or so to see what they are like. They are indoors (in the living room) as we speak. I'm sure that boredom and curiosity will conspire against me and I'll have them opened up again on St Stephen's Day...
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