For woodworkers, craftspeople and furniture makers, using programmable moisture meters are the most reliable means of determining the moisture content (MC) of any wood stock before beginning a project. Nothing is worse than spending hours and money on high quality wood just to have it warp or twist because the wood’s MC is too high. Many woodcrafters are turning to air-drying their own stock, and in doing so, are saving at least 50% over kiln-dried wood or lumber. Like any DIY expert, you should have an idea of how much effort, time, knowledge and room for stacking and storing it should take.
At Anderson-Tully Co. in Vicksburg, Mississippi, their hardwood-processing facility air dries and then kiln dries approximately 70 million board feet of hardwood, which includes about 65 species, each year. At the Vicksburg facility, they air dry the boards to a 25% MC, and then kiln dry the boards for a further reduction of 8%. When air drying boards, there are a number of considerations including the type of species you select. Some species of wood have more or less MC than other species; however, without a kiln you should try to achieve 15-20% MC in sunny and temperate conditions.
Once the wood or boards are brought inside, they’ll reach the appropriate equilibrium moisture content (EMC) as the wood will continually lose or gain moisture until the amount it contains is in balance with the relative humidity (RH) and temperature of the surrounding environment. The amount of moisture at this point of balance is the EMC of the wood.
According to the U.S. Forest Service’s Forest Products Laboratory, it takes 1” thick green boards 45-60 days to air dry to reach the recommended 15-20% MC. If you live in colder and damper climes, you can expect the air drying time to increase. Once the boards have been brought inside, expect further reductions of the EMC to continue for another three to four months. However, it’s worth it if you can start any project with a good stack that’s ready to be worked.
Interested in building your own seasoned stock? Here is a list of tips that can assist with your efforts:
- When storing boards, pick a spot that is open but avoid damp, low, boggy areas or placing the
boards under trees so that twigs and leaves won’t litter your stock.
- Paint the ends of the boards with latex paint; Wood Magazine suggests a commercial sealant such as Sealtite 60 or Mobilicer-M, or place double side-by-side stickers under them. Use soft wood or low-grade lumber for the stickers, and be sure to cut them all to the same exact size or you’ll have warped boards.
- Level the stack’s foundation, and provide a slope for drainage.
- Select defect-free, straight-grained boards no thicker than 2” and less than 12” wide.
- Continually inspect the stack for stains or mildew, which indicates that it may be drying too slowly.
- Invest in a moisture-measuring meter for accuracy, and check it every two weeks while the boards sit outdoors and after moving them inside.
Happy Drying! There are tons of experts here…so ask around! ;-)