From Professor Gene Wengert, forum technical advisor:
The first step in drying oak lumber is to determine what wood you have. The four different oak drying groups are red upland, white upland, red lowland and white lowland. As a general rule, lowland means that the rings are spaced more than 1/4” apart.
Next, determine the quality of the wood. Look for signs that the wood has been previously dried, perhaps air dried. If someone else started the drying process, they may have surface checked the wood. You cannot heal these checks and may actually make them worse even with normal drying.
Also, look at the lumber to make sure there is no shake (a separation parallel to the rings rather than across the rings; potentially a foul odor as well). Virtually all shake indicates a bacterial infection in the wood and such wood is difficult or impossible to dry without checks, honeycomb, and so on.
Check the wood for excessive fuzzing from sawmilling. Fuzz indicates tension wood. Tension wood is very weak and also results in fuzzing when machining.
Check the grain pattern for any quartersawn grain. Quartersawn lumber requires about 15% longer drying time.
Check the grade, as lower grade lumber has more knots and grain deviations, which mean more warp and checking around the knots.
Be aware that circle sawn lumber has as much as 10 times more likelihood of checking compared to band sawn lumber.
Check the thickness. Non-uniform thickness can mean that thinner pieces will be able to cup more easily. Thicker lumber takes longer to dry; 10% thicker takes maybe 15% longer to dry.
End coating, which should be done when the lumber is first sawn for the best benefit, will prevent virtually all drying end checks. End checks can turn into honeycomb that can travel down the piece of lumber. A commercial end coating, properly applied, costs about $3 per MBF but the benefit is often over $30 per MBF.
Forum Responses
(Sawing and Drying Forum)
From contributor J:
Dipping is seldom done in the northern climates as the wood is cool enough that fungi are not exceptionally active. Southern oak may be dipped, but there is also an enzymatic grey stain (non-fungal) that gets into the sapwood if drying is not done immediately, so dipping is not a cure-all. Dipping can give one a false sense of security, so they delay stacking the lumber and some quality loss is therefore likely.
Step 1, Assessing the Raw Material
Step 2, Stacking
Step 3A, Measuring Moisture Content
Step 3B, Sample Boards
