I would propose that kiln-dried wood (in particular steam kilning) is sometimes inferior to naturally cured wood.
Advantages of Kiln Drying
- Kiln dried lumber is more readily available
- Much faster than alternative drying methods
Disadvantages to Kiln-Drying
- Loss of Character
American Black Walnut is a great example of a wood that suffers when kiln dried. The wood looses tremendous character when it is dried in kilns. The heart-wood and sap-wood boundary is not nearly as vivid in kiln died walnut. This can be considered a benefit if the wood is used in certain commercial situations such as flooring. However in fine woodworking the loss in character is generally not desirable.
Another wood that I have noticed a difference in character between kiln dried and air dried is American Cherry, where the general depth of the color is noticeably muted in kiln dried cherry boards.
- Potential Drying Defects
Improper kiln drying can lead to some drying defects that may be difficult to see to the unaided or untrained eye. Examples include honeycombing and case-hardening. These during defects usually render the lumber unsuitable for most fine woodworking and can also pose danger when working the wood in certain situations.
Advantages of Air Drying
- Less Chance For Drying Defects
The biggest defect from air dried lumber is improper moisture content and perhaps warping due to poor stacking techniques. Problems such as case hardening and honeycombing are not found in air dried lumber.
- Better Color Retention in Certain Species
The difference in color and character between kiln dried wood and air dried wood of the same species is unmistakable for certain species as mentioned above. Walnut and cherry are the most easily distinguished, although I am sure there are others.
Disadvantages of Air Drying
Air drying is just plain slow. The general rule of thumb is 1 year + 1 year per inch in thickness.
Properly curing wood usually takes lots of good dry space. For most lumber operations this is a luxury that is tough to justify.
Overall kiln dring is hard to dismiss as a viable way to bring wood to market. Most of the wood I have used over the years was kiln dried and very little of it suffered from any of the drying defects listed above.
However it should be noted that due to the potential loss of character in certain species of wood, air drying should be considered if you are looking to work with these woods or want to highlight the natural character of woods with very dissimilar sap wood and heart wood.