The wood world is full of anecdotal claims from wood suppliers and woodworkers about the process of drying lumber, and which process yields a better, more stable product. Although some of the claims can be chalked up as folklore, the discussion is one of the most important in the lumber industry. This issue of moisture content weighs heavily on the minds of everyone involved with wood.

Before kilns, all wood was air dried and, because it is the 'old' way, this process is usually highly respected. Although it sounds simple, air drying lumber properly is a long arduous process involving sticker stacking, waxing, moving, constant checking and restacking. The invention of kilns and the ability to dry lumber more quickly was of great benefit to the wood world, but there is a question about what the process of kiln treating does to the lumber and how stable the resulting product is. The drier the wood, the stronger but also the more brittle it is. Although some believe that it does not matter how the lumber got that way, air or kiln, there is research to suggest that air drying can result in a stronger and more elastic product. The Encyclopedia of Wood cites a 40% greater modulus of rupture (strength/hardness) without heat and or moisture from kiln treating and up to 15% greater modulus of elasticity (can expand and contract with changing equilibrium moisture content conditions without splitting or cracking at glue joints). This doesn’t mean that kiln drying should be avoided, but it is a reminder that kiln operators must be careful, constantly managing the load and monitoring the temperature and humidity. In order to yield the best product, the kiln operator needs to be experienced with the species of lumber and ratio of heat and time needed to reach the desired moisture content, without forcing it to conform to their latest delivery schedule.

At CSWoods, because of our dry climate, we can air dry lumber to around 7%. This process takes years and attentiveness, tying up capital and inventory. On site, we use a solar kiln and a dehumidification kiln, and we will soon be installing our own vacuum kiln to speed up the process. This will allow us to carefully dry wood for clients in a week, ensuring that they are getting the most stable product possible. We are constantly working to educate ourselves, our suppliers and our clients about drying lumber, and the right moisture content for their region.