Case hardening in white oak

      Is case hardening common in white oak, and should it be accepted? July 18, 2000

Just curious if you drying experts could tell me if this is a common occurrence. I buy a lot of hardwood, especially quartersawn white oak, and 90 percent of the time the wood I get is case-hardened. This is very aggravating.

Do the kilns you buy from use steam injection during the drying process? This is necessary to prevent the outside of the lumber from drying faster than the inside. If they do not use steam injection, then find a kiln that does.

Also, white oak is a real tough wood to dry properly. I would think that air drying for 6-plus months, then a slow (assuming 4/4 lumber), steam injected, kiln dry to the final 6 to 8 percent moisture content would lessen the chance of case hardening.

Have you thought about buying the lumber green and air drying it yourself? The kilns you are buying from may not be air drying the lumber long enough before starting the kiln drying. And, to maximize their throughput, they may be using a kiln schedule that is to aggressive for white oak.

Case hardening is a defect and should not be tolerated. It can, and in most cases is, relieved in drying. Chances are your supplier has a dehumidification kiln without steam or other methods of relieving the stress.
Gene Wengert, forum moderator

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