Bill Tindall
Among some there is a notion that kiln dried (KD) lumber is inherently defective, inferior or what ever and that the cure to these ills is to use air dried lumber. The two issues that are most often raised by the advocates of air dried lumber are color and stability. The purpose of this post is to challenge these myths with facts about KD lumber.

Stability: Modern kiln drying operations have from several hundred thousand to several million bdft capacity to dry lumber which translates to several hundred thousand to several million dollars at risk in these kilns. Any company that chooses to stay in business will devote what ever resources are necessary to ensure their KD product meets the needs of their customers.

A factory turning KD lumber into wood products places no less demands on the workability of their lumber than the individual woodworker. These companies have the experience to know when lumber is not up to specification and the clout to make claims against the supplier when it is not.

It therefore logically follows that a modern KD operation runs their kilns to provide the best product they can to their customers. When it comes to stability "best" means that the rate at which moisture is removed from the green wood is precisely controlled to avoid stress. As an example, the large KD facilities in my area put lumber on sticks soon after it is sawed and then move this lumber to a controlled environment, for example a predrier, where drying conditions can be controlled. When this predrying process is complete the lumber is moved into an environment where the temperature and air flow can be regulated to uniformly remove precise amounts of water from the lumber each day. The rate of water removal is precisely controlled to avoid excessive moisture gradients in the wood that would result in stress. This last process is called kiln drying. To some, I suppose, KD may imply that the lumber is baked in an oven till its done, which sounds bad, and it would be.

An individual drying wood in their back yard has little control over the rate at which moisture is removed from a lumber stack. It is certain that the rate will not be uniform through out the pile. If the lumber drying fastest in the pile dries slower than the rate in a commercial predrier and kiln the product from the back yard can be as good as the KD product. However, if the drying rate is too small discoloration can occur.

Color: The popular example here is walnut. Air dry advocates claim that air dried walnut has colors and variations in color that are more attractive than the brown of KD walnut or the more uniform brown of steamed and KD walnut. Most commercial walnut has been steamed. (I have seen no difference in KD- not steamed and air dried walnut on a fresh planed surface)

The colors of walnut are fleeting when it is exposed to sun light. Fresh off the saw walnut can be yellow or green. It soon turns to purples, reds and browns. Eventually it turns brown and eventually light yellow-brown. Several times I have posted a picture of matching pieces of walnut air dried vs steamed and KD after a few months exposure in a sunny room. There is hardly a detectable difference between them. After a year there will be no detectable difference. I can post again if there remains a skeptic.

Commercial operations get their lumber on sticks quickly. They may even dip the lumber in antifungal chemicals. As a result lumber from these sources remains bright and stain-free.

There are lots of valid reasons to air dry lumber, access to a kiln being the most common. There is no need to rationalize one's desire or need to air dry lumber by claiming a mythical quality advantage.

That said it is certainly possible to screw up a load of lumber in a kiln, or the air drying before the kiln. In my experience these screw ups occur in tiny KD operations (small, package dehumidification kilns) with distressing frequency. They would be rare to nonexistent in the large KD facilities.