The need to get to 7%

[Clevelander]

I specialize in live edge slabs over 36" wide. I bring them down to between 7-9% moisture content in my dehumidification kiln. I store them in a non-humidity controlled environment. Within just a few days the outer slabs are back to 15% +-. I have had zero callbacks or issues selling and using them at this percentage. If they are going to go back up to 15% is there a need, if so, what is the need to take them to 7% to begin with?

Thanks

[firefighter ontheside]

I would find it hard to believe that the MC content of the center of a 8/4 slab would go back to 15% in such a short time if it truly was down to 7% at the center.  

I think the projects that people are making with large live edge slabs are not prone to wood movement problems.  If I make a breakfast bar with a big slab, it shrinking a small amount isn't gonna be noticed.  Nobody is building a cabinet with large slabs.

I'm in the same boat with you.  Currently I'm air drying down to similar as you in MO.  I'm going to build a kiln, but I don't have a controlled enviro to store in afterward, so wood will begin to take in moisture again. I'll have to try and sell stuff soon after drying.  Maybe sell in units, but that usually means giving a discount per bf.  

I'm interested what others will have to say.

[GeneWengert-WoodDoc]

If dry wood could gain moisture that fast, it would also lose moisture that quickly, but we know it does not.  Also, to achieve 15% MC, after being at 7% MC would require exposure to humidities well over 80% RH, but the average outdoor humidity is 65% RH or 12% EMC.  Even if the wood is exposed to really high humidity, it does take many weeks or months for the core MC to change.  So, it would seem that there is some sort of moisture measurement problem.

Are you using a pin meter?  Are the needles insulated?  Does the meter read a low MC when you check some dry wood in your house within a minute of your 15% MC readings?  The house we know will be around 7% MC?  Is there perhaps some condensation on the meter that is shorting out the meter?

[YellowHammer]

Among other things, I like to dry down to past what a customer may reasonably subject any of my wood. I consider it a stress test. If a board has been to 7% with no defects then goes up higher I can reasonably assume the board can again go down and will behave. I would have seen any poor behavior, cracks and already corrected it or culled it when subjected to low moisture values.

I never want a board to go down lower for a customer than I have taken it myself.  Bad phone calls happen.

[GeneWengert-WoodDoc]

Y-H is right on target.

One reason this works is that shrinkage causes splitting or cracking, while swelling does little to the appearance.  Second, when we reverse direction, going from losing moisture to gaining moisture, there is a lag, called the hysteresis effect, which essentially says that there is about a 1% MC lag or delay when you reverse.

[scsmith42]

Among other things, I like to dry down to past what a customer may reasonably subject any of my wood. I consider it a stress test. If a board has been to 7% with no defects then goes up higher I can reasonably assume the board can again go down and will behave. I would have seen any poor behavior, cracks and already corrected it or culled it when subjected to low moisture values.

I never want a board to go down lower for a customer than I have taken it myself.  Bad phone calls happen.

I do the same.  It eliminates a lot of problems.

[moodnacreek]

Due to the demand, I keep more than 10 m of thick/wide un edged stuff on sticks. I do not have a kiln or time to do anymore expanding.  These planks are 2 1/4" thick and as wide as 22". I will not do; oak or ash and do all the cedar, soft maple, cherry, walnut and sassafras I can get. It is important that the user 'paints' the top surface first with the end grain and the bottom leaving a strip bare in the center. This will allow moisture to escape and reverse the cup that could happen. Also the 'bread board' on the ends is a no no.

[logboy]

I specialize in live edge slabs over 36" wide. I bring them down to between 7-9% moisture content in my dehumidification kiln. I store them in a non-humidity controlled environment. Within just a few days the outer slabs are back to 15% +-. I have had zero callbacks or issues selling and using them at this percentage. If they are going to go back up to 15% is there a need, if so, what is the need to take them to 7% to begin with?

Thanks

Let me guess: youre using a Mini-Ligno moisture meter, and even with the temperature correction chart its saying they're 7-9% in the kiln at 120F, but 15% at 70F?  I ask because I had the same problem many years ago before I upgraded to a proper moisture meter. Your slabs aren't gaining moisture, they're just not dry yet when you're yanking them out of the kiln. If youre using a cheap meter, junk it and spend the money on a proper one with deep probes for slabs. It will be expensive, but still cheaper than a ruined reputation and lost sales from selling wet slabs. After handling thousands of slabs, I use a two part method to check moisture. First, I lift one end. I can tell just by lifting a slab whether its close to dry or not. Dry slabs are light, wet slabs aren't. Then I use my meter to verify.