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Hi, folks. There's a general rule that's been floated around here(and elsewhere) that basically states, "X number of months per inch of thickness" when drying/seasoning boards for luthiery use. Anyone remember this? Can you tell me what it is, please? Thanks.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Pretty sure it's 1 year per inch of thickness. Make sure you seal the ends of the boards to avoid checking.

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I've heard also 1 year per inch of thickness, after resawing. What a forest engineer once told me is the best way to dry wood, whit a minimum of warping, twisting, bowing, etc, is to go ''step by step''.

You have a tree, you want necks.

Cut 36'' logs (or whathever lenght you need), seal the ends, let it dry like this few months, inside, or outside, covered to protect from rain (+ snow and ice, here). After few months, resaw quarters of 16/4 beams, stick it and let it dry few months, resaw it smaller later. Finally, you get out our necks are 7/8'', 11/16 if the wood is pretty stable, and let if dry again a bit before planning it down to 3/4 and begin to work it.

This way, wood release its stress at each step, slowly but surely. If you take a huge 16/4 beam and resaw it immediatly to 7/8'' neck... you'll release a lot of stress at once, and you'll get more warping problems, and the center of the beam will be less dry, for sure.

That's how I do.. maybe i'm too maniac but... If you can save 1/16'' or 1/8'' at each step, it can result in 1 more neck, 1 more top, 1 more back from your billet.... Suck out the max of the beam!

My 2 cents
Francis

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Francis Richer, Montréal
Les Guitares F&M Guitars

Depends on the wood and conditions. In some Cedars the heartwood is close to EMC before they are cut down and some tropical hard wood can take multiple years/inch. Best thing to do is weigh a small scrap cut from the center of a board in the center of the stack with a postage scale or other precise scale; bake it in an oven at 200 until its weight stabilizes at a low point (oven dry weight).
MC% = (initial weight - oven dry weight) x 100
(divided by) oven dry weight

Thanks guys. One year per inch it is.
Ti-Roux, you are a maniac. lol! But I agree, suck out all the board feet you can. And get the most out of everything else you're using as well.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

What I've been told differs a bit from Ti-Roux's instructions, but it's worked well for me.

Basically, you want to get the moisture out of the wood as quickly as possible (to avoid rot, mildew, and so on) without damaging it through excessive shrinkage. The big problem with shrinkage is the different rates of radial and tangential movement: the diameter of the log doesn't decrease in proportion to the circumference, usually, and that's what gives you checking. I've got some small pieces of dogwood that were quartered at 90 degrees on the bandsaw, and the included angle is now more like 85 degrees.

One outcome of this difference in rate of shrinkage is that if there is curvature to the annual ring lines on the end of a board, they will tend to straighten out as it dries, and this causes cupping and warping. So, one way to minimize drying degrade is to cut wedges along the radius that are thin enough on the wide (bark) side that there is not a lot of curvature to the rings on the end. The included angle on the wedge will end up a little smaller than when it began, but with any luck you won't get checking.

Another thing that seems to help is to equalize the rate of moisture loss through all the surfaces. Bark is waterproof, so removing it while the log is green helps. Most woods lose moisture most quickly through the end grain, so you need to seal that to some degree. I've found (with spruce and maple) that a couple of coats of latex paint on the ends does the job.

When a buddy and I got a spruce tree we split it into billets about 2" thick on the wide side. These we square stacked: alternate layers at 90 degrees to each other, on pallets in a shady place. We covered the tops of the stacks with overhanging plywood and tarps to keep off the rain, but allowed circulation around the sides of the stacks. We turned the stacks after a month, to get wood from the bottom to the top, and inside out, and did the same a couple of months later. By then the wood was dry enough to move indoors. I got a lot of good brace stock and fiddle tops from that tree, after waiting a year or two for it to season a bit more. I'd wait longer with hardwood.