I know the "rule of thumb" is one year per inch to air dry lumber. But, all lumber dries at different rates. How long does white pine take to air dry? Thanks
P 156 of Hoadley's "Understanding Wood" in Table 8.2 gives a range of 60-200 days for green 4/4 eastern white pine to air dry to 20% MC. Footnote reads "Minimum days given refer to lumber dried during good drying weather, generally spring and summer. Lumber stacked too late in the period of good drying weather or during the fall and winter usually will not reach 20% MC until the following spring. This accounts for the maximum days given."
It's possible the conditions under which it is exposed will significantly impact the drying time (inside or out, covered, off ground, sticker spacing, et cetera).
The two keys are air flow and humidity. You cannot control humidity, but you can do something about airflow. Be sure that the stack is open to the air on all sides by at least 5 or 6 feet preferably. 4 feet is better than 2 and 6 feet is better than 4 for example. You could also use a small box type fan to keep the air moving across the lumber to set up the drying force. Some species can be dried faster than others. Oak has to dry slow, so using a fan to increase airflow could cause checking and case hardening. For pine, that is not an issue and a supplemental fan to increase airflow will decrease the overall drying time to the lower end of the Hoadley range. You could run the fan during the day and turn it off at night to let the lumber go through a conditioning phase where the core comes back into equilibrium with the shell like occurs in a solar kiln. The one sure thing is that too little air flow will lead to stain and mold of the lumber. Don't ask me how I know this!
I am thinking about building a solar kiln, and I have been doing some research on solar drying. There are a lot of advantages.
I am not going to contradict Bruce H and the scientific camp but.. He leave one MAJOR factor out in his book. When the log is felled. Winter cut or other. If the log was felled when the sap was down(winter-Jan) the drying time is shorter and the timber in better. In the olde days in New England, most of the big timbers were cut in the winter to help with movement. Easier to sled than cart with wheels. At the same time, the wood was drier at the moment it fell.
In my experience, oak and pine cut in the winter has been superior to the summer lots. I make a point of harvesting my wood in the cold months and it has been the biggest factor in successful wood supplies.
Sometimes you don't have a choice and you go with the flow.
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