Preventing Drying Damage to Oak
Advice on controlling the drying conditions for Oak. December 6, 2009
Does anyone have trouble with degrade on oak when drying with a dehumidifier kiln? I air dry first but I seem to have better results from green. It's that last drying from 16%-10% that seems to create problems. Has anyone tried adding water in the kiln at the end of drying to get good results?
From Professor Gene Wengert, forum technical advisor:
Except for cup, all other degrade is the result of improper drying at much higher MCs... above 45% MC for oak. Because the wood is so strong at 16% MC, it is virtually impossible to initiate new checking or honeycomb degrade. Further, staining is also a high MC event. Because air drying is uncontrolled (drying rates can be too fast or too slow, and rewetting can occur from rain), air drying can cause a lot of degrade. That is why shed drying is often preferred for oak.
Adding water to partially dried lumber can create a tremendous amount of interior checking as well as some surface stain.
From the original questioner:
I have just loaded the kiln with oak at 20%, air dried boards, initial kiln temp of 38 degrees c, but wet bulb of 29 degrees. I am worried that I cannot control humidity for a safe drying rate. Any suggestions?
From contributor T:
As Dr. Wengert said, I also tell people that once the wood is below 25% MC, you generally cannot do any drying damage. If anything, I would raise the temperatures up some if possible, to speed the drying. Oak and other species that require more controlled drying are best put into a kiln green, where you have the ability to control the conditions.
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KnowledgeBase: Knowledge Base
KnowledgeBase: Primary Processing
KnowledgeBase: Primary Processing: Air Drying Lumber
KnowledgeBase: Primary Processing: Kiln Operation
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