J. Gibson McIlvain is a timber importer which sources lumber from all around the world. Each geographical area and individual lumber mills have their own distinct methods of operation when it comes to pre-drying their wood. While most imported timbers are dried to a moisture level of 12-15 percent (the European norm), domestic wood can be air dried to a moisture content of 10 to 25 percent (see Part 1).
While different handling procedures are used depending on the dryness level in which the lumber is received, the same basic process may be followed for almost any board. The overall period from the moment the lumber arrives in our yard to the time it’s ready to be sold and sent to a jobsite will vary greatly and be dependent on the wood type and its level of dryness.
Air-Dried Wood
The back corners of our Maryland lumber yard are dedicated to the air-drying process. Almost every piece of lumber we get is stacked and stickered in those back corners. Stickers are essentially spacers that allow air to circulate over the entire board, allowing for even, thorough moisture release. As you may assume, the more moisture the wood contains, the longer it will take to dry naturally. We usually paint or wax the ends of the boards to prevent checking and cracking by slowing down the release of moisture. Air drying is a safe approach to get rid of the bulk of excess moisture, because it is gentle on the wood.
Because air drying does not allow the lignin to “set,” air-dried wood will not be as stable as kiln-dried wood. (In exchange, air-dried wood will be softer and typically simpler to deal with.) When wood is air dried, it reaches a state of equilibrium with the surrounding climate; this process can take weeks or nearly a year. If kiln drying is planned, air drying will help the wood to be prepared for the next step.
Kiln-Dried Wood
After the wood has acclimatized to North American humidity levels, it can safely begin the kiln-drying process to help it reach a moisture content of 6-8 percent. Because the boilers are heated by offcuts and dust created by our own mill, the kilns we utilize at J. Gibson McIlvain are quite environmentally friendly. Kiln drying time and temperature are determined by the species and density of the material. Denser wood may take up to a month to dry, while some species may just take two to three weeks inside the kiln. To avoid hardening or other types of damage, we make certain to heat up and cool down the kilns slowly.
Improper drying frequently causes harm that isn’t noticeable until you’re over halfway through your project. We take our time and properly dry all of our timber, so that our customers don’t have to deal with the delays and additional costs that occur when their lumber fails.
