Q.
We recently put 8/4 red oak in our dehumidification kiln stacked at the top of a load of 4/4 oak. The 4/4 dried in good condition but the 8/4 had many surface checks. I had the controls set at 85 degrees F at the start of the batch and was only removing about 1 percent moisture content (MC) per day until the lumber reached 25 percent. I then increased the temp to 100 degrees F. Any ideas on what went wrong and how we can prevent this from happening in the future?
A.
Did the one percent MC per day come from the 8/4 or 4/4? In general, 8/4 must be dried 2.5 times more slowly than 4/4.
What went wrong is that you dried the 8/4 too fast -- perhaps it was just a few hours every day that were too fast and then a few hours were too slow; the effect is damage to the lumber when drying too fast, even though the daily loss is ok.
You need to read "Drying Oak Lumber." Pub: Univ. of Wisconsin-Madison. Order from 608-262-9975. About $30.
- Gene Wengert, forum moderator
