Q. We seem to be having more troubles with cypress lumber. Problems include cupping and brittleness. We are in Colorado where conditions are dry, so we like to get fairly dry lumber when we order. What can we do better?
A. Cypress, often called baldcypress, is a magnificent tree here in the South. The lumber has a pleasing grain, so it often desired for paneling.
Drying is difficult, compared to the pines. As a result, the kiln operator needs to know the unique characteristics of this wood in order to dry it correctly.
Here are three issues with drying.
1. The lumber has a tendency to develop surface checks and end checks.
2. The wood is also known to develop water pockets -- small wet regions within a piece of lumber (perhaps 20 percent MC) while the rest of the piece is 10 percent MC. To avoid wet pockets, often the lumber id over-dried.
3. From a machining standpoint, the lumber is best if between 10 to 12 percent MC. The lumber becomes brittle if dried below this MC. (You cannot store over-dried lumber in a humid location in an attempt to repair the brittleness.)
With this background info, I suspect your lumber is over-dried, perhaps by mistake or perhaps because you have asked for very dry lumber. Certainly, if you ask for 10 to 12 percent MC lumber, it will dry to 6 percent MC in Colorado, which also means around 1 percent shrinkage in width.
You need to make sure that you machine the lumber at a higher MC. You can then let it dry further in Colorado, or have a design or product that can accommodate 1 percent shrinkage as the wood dries to match your low humidity conditions.
Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 35 years. He is extension specialist emeritus at the University of Wisconsin-Madison.
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