4/4 White oak checking

[MIsawyer]

Had some white oak take a beating while air drying.  Now I am putting it into the kiln and there is some significant surface checking.  My moisture is in between 30 and 35.  Any thoughts on drying this

[beenthere]

Thoughts:
Only that the surface dried and shrunk, while the interior of the boards didn't dry and didn't shrink. Causes surface checks.
In the kiln, the interior will dry and shrink, closing the surface checks which means the surface has taken on a set and likely interior checking (referred to as honeycomb) may happen.


Goes with the very delicate drying nature of white oak. Have to babysit it from day one of sawing.

[WmFritz]

A couple more thoughts:
Was your stack inside or outside air drying?
How thick were  your stickers?
How much air was moving through the stack?

[Den Socling]

Don't get your hopes up. White Oak is non-porous because of occlusions. Water comes out fastest at the rays. Wood shrinks next to the rays and you have surface checks. If you let the surface get too wet, it will swell and tear the checks deeper. If the shell gets too dry, it will set and you end up with the HC mentioned by bt. I don't run conventional kilns but, if I was in your shoes, I'd treat it like it was wet. Where are you getting the 35% reading? The core is probably much higher.

[scsmith42]

Did the stacks get repeatedly wet (rained on) while air drying?

[GeneWengert-WoodDoc]

The checks you see now are previous checks that are reopening.  Fast drying now can make them worse, but not create them at this low MC.  Rewetting or using a higher than suggested humidity will worsen them too.

[MIsawyer]

It did not get rained on while air drying.  I got the 30-35% from four samples that I did the oven test on.  Thanks everyone

[Den Socling]

Did you bake cross sections for the oven test or did you separate shell from core on cross section? What I'm getting at is this. If the core is actually 30-35%, you are almost in the clear. If the core is actually something like 50-55%, damage can yet be done.

[GeneWengert-WoodDoc]

When we have oak with preexisting checks (we can cut check samples when we cut the moisture samples), we need to start the kiln at an EMC equal to the average outside EMC which will also be the surface fiber MC.  If surface MC and kiln EMC are equal, then very little drying will occur at the start.  We do not want the kiln more humid than this and also not much drier.  We should start at 105 F or cooler, but getting the correct humidity is a key.  In most cases, the kiln will start at about 65% RH or 12% EMC.  We never use steam or water spray at start up.  We go to 105 F slowly, heating about 5 F per hour to get to 105 F.  Once at the correct conditions, we slowly lower the RH, but not as fast as in the standard kiln schedule.  We also raise the temperature more slowly.  This will protect the lumber from further damage, but will not cure previous damage.  Ok?

[Den Socling]

Good description, Gene.

[MIsawyer]

Thanks a lot Gene and everyone else this really helped

[Denny]

Hey guys I've found that direct sunlight will check up green WO. If I have to keep WO in the yard for a few days, we cover em with pile covers to protect the top and any lengths sticking out of the ends of the packs. Blaring hot summer sun checks up my WO in hours. I'm lucky to have a pre-dryer for my WO.

The key to drying WO is to go nice and easy with it.  Green WO takes me around 35-38 days to dry down to 6%.

[Magicman]

Hello Denny.  You have been mighty quiet for almost a year.  How about an intro thread and sharing your lumber/woodworking interest.  Also adding your location to your profile will help.   ;D

[thecfarm]

Sounds like Denny has dried some white oak a couple times.  ;)

[GeneWengert-WoodDoc]

I think we all know what is meant when we say that direct sunlight can check oak.  This concept is why a roof for an air drying pile is so important for oak...in fact, open sheds are better than typical air drying, especially thicker stock.

For the record, the sun does not check the oak, but rather the heat from the sunlight and the low humidity created by the heat, do the damage...checking is caused by drying too fast, which in turn is caused by low humidities and high air flow.  Heat weakens the wood so the "normal" stress level becomes too much for hot wood.

[Denny]

Hello Denny.  You have been mighty quiet for almost a year.  How about an intro thread and sharing your lumber/woodworking interest.  Also adding your location to your profile will help.   ;D

Magicman, thanks for the reply. Yes, I have been quietly learning from you folks for a whille now, its about time I started talkin' to you guys. I will start an intro thread ASAP. Excuse my ignorance but should I post something like that in the General Board or the Drying and Processing section where I spend 99% of the time ?

Heading to profile to update my info too.

Dr. Wengert, thanks for your reply. I should have been more clear when I said "sunlight".