Improper Drying

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Forum topic by onglueme posted 01-22-2019 03:04 AM 702 views 0 times favorited 5 replies Add to Favorites Watch
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21 posts in 833 days

01-22-2019 03:04 AM

Topic tags/keywords: drying kiln walnut slab slabs moisture checking

I have imported Peruvian walnut slabs from Honduras. They are 3 inches thick and kiln dried aggressively for 3 weeks. A very short time, I know. I am new to the industry and I had, unwisely, relied on local expertise. Upon completion, the slabs registered 6% MC. Once shipped and delivered and after checking a small sample, the MC inside was much higher and checking was visible. What are my options? Is there any comeback? Should I just leave them out to continue drying or should I find a kiln that can properly finish the job or is it now firewood?

In the future, I think I will just leave the slab in a shed in Honduras to naturally dry but my only concern is that the country is quite humid many times of the year. The shed would be inland and hours away from anybody if water. Any advice would be greatly appreciated.

I am new and trying to break into the industry. Also working with FSC to acquire certification.

Thanks in an advance.


5 replies so far

View Firewood's profile


1346 posts in 2556 days

#1 posted 01-22-2019 03:30 AM

From your description, and photos that the lumber is suffering from case hardening. Here is a description from Wikipedia:

Case hardening describes lumber or timber that has been dried too rapidly. Wood initially dries from the shell (surface), shrinking the shell and putting the core under compression. When this shell is at a low moisture content it will ‘set’ and resist shrinkage. The core of the wood is still at a higher moisture content. This core will then begin to dry and shrink. However, any shrinkage is resisted by the already ‘set’ shell. This leads to reversed stresses; compression stresses on the shell and tension stresses in the core. This results in unrelieved stress called case hardening. Case-hardened [wood] may warp considerably and dangerously when the stress is released by sawing.

At this point, I don’t know if the lumber can be salvaged. Perhaps someone a lot smarter than me can provide some advice.

-- Mike - Waukesha, WI

View onglueme's profile


21 posts in 833 days

#2 posted 01-22-2019 03:37 AM

Thanks Mike,

I did read about case hardening which this certainly is. I just need to know if I should spend the time and money to move it from storage to some open space, stacked with some weights for a year or two and the likelihood of the wood being usable in the future.


View AZWoody's profile


1478 posts in 2146 days

#3 posted 01-22-2019 04:33 AM

See if anyone in your area has a kiln that can add steam. That is used as a way to help relax the wood while drying to help keep case hardening from happening. I don’t know if it can help fix it after the fact but worth a shot.

Also, might be good to ask at the forestry forum also. That’s full of people who do these kind of things for a living.

Loads of info there.

View Aj2's profile


3507 posts in 2720 days

#4 posted 01-22-2019 05:41 AM

There’s no fixing honeycomb drying defects.
Firewood for sure

-- Aj

View Wildwood's profile


2911 posts in 3056 days

#5 posted 01-22-2019 11:31 AM

This chapter will give you pretty good overview.

Don’t know any kiln operators in the U.S. that would recommend or like to attempt to dry slabs three inches thick without warning you about defects.

Might be able to salvage some of that wood!

-- Bill

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