drying 8/4 walnut

[Downhill Cutter]

G'Morning, Forestry Forum.  Happy Christmas to all of Y'all.

I have a Nyle L 53 kiln I've been learning about for a year or so.  Word got out locally, and a man brought me ~200bdf of green 8/4  walnut  (8-10" x ~ 10') to dry for a kitchen island.  (side question . . . would any experienced operator take on that job?  If so, how in the world do you charge for that?)

The material was green,~~32-33%  at 1/4 AND 3/4" depth.  I was waiting on an electrician to do a couple of repairs for me, so I stacked the material on stickers in the kiln,  turned on a shop-ventilation fan to move the air around and let it sit for about a week. 

Electrical problems resolved, I followed the manual re: settings, and let her buck.  Initially I got a couple of quarts of water out, then nothing.  When I finally called Stan @ Nyle, he was able to tell me that I was not the first guy to try to reduce the wet-bulb setting to get a bit of moisture out of the load.  :-\

I let the kiln operate for a few days.   One of the first things to happen is that the wet-bulb sensor shot up to equal the dry-bulb.  I'd tried to use too short a piece of wick in my water tank, and the wick was dry over the sensor.   After resolving that BGO (Blinding Glimpse of the Obvious)  wet bulb still failed  to consistently rise to and maintain settings, compressor functioned only sporadically, then not at all.  Moisture meter showed 14-17% at 1/4", and 32% at 3/4.  and one of the boards had some RIGHTEOUS splits 12-18" in from both ends like I've never seen.  Finally, an couple of days ago, I shut down the kiln computer to let the material rest and maybe equalize a bit.    I kept one of the kiln fans on , just to keep air moving,  and that's the current state of play. 

I'm considering dumping some water on the floor of the kiln and running a "conditioning" cycle, to un-case-harden the material . . .

I'd appreciate any suggestions.  

Thanks in advance.

DownHill Cutter  

[boonesyard]

I wouldn't dry green walnut in the kiln until it had air dried to 20% or less. Walnut can be as tricky and stubborn as oak.

[Southside]

I think you are about to the point of having to sacrifice a few chickens and perform a Santeria ritual with the blood on the kiln door.  However, just in case there are any other options left @YellowHammer might could chime in.  

[YellowHammer]

Drying 8/4 walnut from green is a very challenging cycle, and if there is only 200 bdft of green in the kiln, it will be even more so, because it causes an underload condition in the kiln, and walnut is cranky anyway.

I always air dry green walnut for at least 6 weeks or longer to get the moisture down to 20% or so, before I put it into the kiln.  I realize this isn't always possible, but its a good idea.

Generally, when the wick is dry, it means the WB is so low that it dries out the wick before the wood.  This makes your WB and DB match, and is a sure signal something is going wrong inside the kiln.  It can also mean the wick is crusty, so the first thing I'd do is cut it back a few inches and get some fresh wick on the sensor.  Typically, it means the air in the kiln is very, very dry, "too" dry.

The splits are caused by too much case and core differential, which means and the problem is that you still have 32% moisture in the wood, which is still way too high to suck moisture out at an aggressive DB setting, and without still cause drying defects. Generally the wood isn't in the safe zone until maybe 15% to 20% core.  So you can still make the cracks worse.

The wood is showing that it doesn't matter how dry the kiln is, it will only dry so fast.

So now the question is how much time do you have?  It going to take at least 3 weeks, maybe 4 to finish this load in the kiln, assuming it's not bacterially locked up, which would take longer.

I would try to get the case to core more equal by moderating the WB/DB differential settings and raising the temperature, up to 125 and 130, and giving time for the moisture to move to the case and out into the kiln chamber.  If you get to 133F you will trip the freon high pressure switch, so go to these higher temps carefully with the compressor off.  Personally, I wouldn't pour water in the kiln, as there is still enough moisture in the wood to provide all the water you need, however you may need to do it later.  So at the point, turn the compressor off, raise the temperature to 130, and wait for the case and core to get closer together, a couple days or so, then drop the temperature and resume a 120/98, setting, and wait for things to lock up again, (it will) then shut the kiln off, go back up to 130, wait for the moisture to move again (you'll feel the moisture in the kiln chamber go up or use a hygrometer and restart the 120/98 step.  At some point, at go to a 125/95 setting, which is higher than Stan recommends, but the extra 5 degrees can help make difference.  Check the moisture drop every day and at some point the wood may release and you can go back to normal drying, if not, you'll have to walk it down doing this process severe times.  This could be a very aggravating load to dry, but it can be done, it just takes some juggling.  Track your moisture content daily, because its important to see what is working and what is not, and focus on what seems to make the moisture move out of the wood.  Sometimes the best way is to simply kick up the temps to 140F, crack the vents a very little, and let the moisture leave the kiln in the air, slowly, using the vents only.

Place a bucket under the condensate tube exiting the kiln to help give an idea of the moisture being removed.  If water is dripping out, keep the compressor running, because the wood is drying.  If no water is dripping out, then running the kiln isn't doing anything anyway, shut it off, jack up the temp to release some moisture, wait a few days, and hit it again.

Chickens are always a good idea, I'd probably stack up at Zaxby's because it will take awhile to finish this load, and you'll want something to snack on.

[K-Guy]

Check your wet bulb setup also. if you have the sensor to far away from the bottle it will dry out also.

KilnTech Episode 6: Wet bulb/ Dry bulb placement - YouTube

[customsawyer]

I have seen some walnut with enough stress in it that it will cause the splits like you are experiencing. Your aggressive drying isn't helping it but it could be the way it was sawed or the log itself. 

[GeneWengert-WoodDoc]

Green walnut is around 79% MC or so.  Your reading of 30% is incorrect or somehow the wood was air dried prior to entering the kiln.  Recall that all defects, except cupping, are initiated above. 45% MC for thick walnut, so that high MC is also where you will be able to control defects, not under 30% MC.

The suggestion is to always double end coat 8/4 and thicker  walnut.  End splitting is a high risk without end coating.  The coating needs to be applied at 70% MC.  The coating needs to be the best you can afford...Anchorseal or similar.

A wet-bulb should be about 2" from the water and the wick must be clean and new so it transfers water to the wick and to the bulb.  The critical part of the bulb is the tip and about 1" back from the tip.  The wick needs to be changed perhaps every two weeks.  Use distilled water.  If the wick goes dry (reads the same as the dry-bulb) change it then after you figure out what is going wrong.  Make sure you have enough air flow across the wick.

Remember that you have a two speed fan, so if things are not right, use the "off" speed.

[Downhill Cutter]

WOW . . . . Thanks to all of you for your considered counsel.

I'll keep you posted . . . but THANKS in the interim! ;D

Happy Christmas to all of you  

Oh . . . Dr W was correct.  The walnut was not completely green: it had been in a barn, but not on sticks, for a short period of time before getting to me, so the m/c had a chance to drop a bit, just not enough.

[Stephen1]

always worth following along when someone is trying to dry thick walnut. Good luck!

[Downhill Cutter]

 . . . Stephen1, I hope you're just not gloating, since you have the iDry and all . . .

;D

Happy Canadian Christmas, :new_year:

[Stephen1]

. . . Stephen1, I hope you're just not gloating, since you have the iDry and all . . .

;D

Happy Canadian Christmas, :new_year:

Not at all, I have been backed up trying to dry big old walnut. 
I foolishly promised some oak to a lawyer for their construction project, fireplace mantle and some other decorative wood. Well he didn't get his wood in time. It is going in today. 
He started insinuating all these delays were going to cost money.
I replied " Wood is Wood and I can only do what the wood wants. I am doing my best! " 
Calmed him down a bit 
Happy American Christmas!