Q. We final are “biting the bullet” and getting kilns to dry our own lumber. We figure it is lower cost and will be higher in quality. Any advice?
A: I believe, from your question, you already have some equipment purchased. Hopefully, you did not purchase the cheapest unit, but spent enough money to get quality equipment. Almost everyone air dries or shed dries prior to kiln drying, but casual air drying can lead to many drying defects.
Here are three key principles of lumber drying: First, 99 percent of all drying defects develop between the day the lumber was first sawn and the loss of the first one-third of the moisture. It is these high MC levels that require attention if you want quality drying. A second key point for you to understand is that the rate of drying (percent MC loss per day) with this high MC lumber must be carefully controlled to assure the highest quality. For this reason, many people will use a roof over their air drying lumber, sometimes called shed drying. The final key item is that over drying lumber creates cupping, poor machining and poor gluing. Usually, under 10 percent MC is too dry for softwoods (needle trees) and 6.5 to 7.5 percent MC is perfect for hardwoods (leaf trees).
Discussion about the actual techniques for drying would take an entire book to answer. In fact, I wrote a book "DRYING HARDWOOD LUMBER" that is now out of print, but you can download a PDF file for free from the Internet. In fact, the local copy stores will download it for you, copy it and bind it. I also have a document on white and red pine drying…contact me for details.
Next step, after studying this book, is to get training for your drying supervisor and for employees involved in the drying operation. Classes are offered annually in New York, Wisconsin, Kentucky and North Carolina here in the east. (Announcements are given on WoodWeb.com as well as here in this magazine.) You should also join a lumber drying association. These groups meet once or twice a year for training and tours of present operations. There is a lot learned when visiting your competitors' operations.
Lastly, and somewhat self-serving, hire the best drying consultant you can find to provide one-on-one training and also to analyze your processing. Have him visit your operation when first starting up and then maybe six months later. Avoid consultants that are selling equipment, as they may have a different agenda than why you require.
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