About Lumber "Dry" Furniture
For years, I stressed about how the old guys (before 1900, or so) dried their lumber.  I studied. I researched. I asked the right people. There were no moisture meters. There were no kilns. I got nowhere. About five years ago (spring, 2012), I was on a woodworker's tour of one of historic Colonial homes in Charleston, SC. Our guide was the furniture conservator/preservationist for the museum. As he spoke about the local furniture makers of the day using mules to sled virgin poplar and southern yellow pine out of the swamps, I happened to ask him. His response?
"Air dry. Sticker, stack, and air dry. That's all they needed because nothing was environmentally controlled. It swole and shrank with the seasons."
What an epiphany. The truth is, wood moves, and nothing can stop it. As the humidity changes with the seasons, the moisture content of wood changes with it. It swells in the summer as the humidity goes up, and it shrinks in winter as the humidity goes down.
So, What's the Issue?Woodcraft Premium Casters -- © S.C. Rogers
Where I live in the south, average annual humidity ranges from about 60% to 80%. The maps to the left show the February (typically dry) and August (more humid) ranges. This translates to an equilibrium moisture content (EMC) of wood (again, in my area) to a range of about 12% to 15%, depending on the season. That's too wet...
In contrast, modern homes are environmentally controlled. Summer A/C, winter heat, humidifiers, dehumidifiers, etc., all combine to make modern living much more consistent within the confines of our homes. Typically, today's homes range from around 30% to 50% humidity, which translates to about 6% to 9% EMC in your wood products.
Simply stated, this is where you want wood to be for building fine furniure. This is the moisture content that wood will live in within your home, and the goal is to minimize movement after construction. This is where you want the wood to be when you build with it.
So, What's the Fix?Equilibrium Moisture Content -- © U.S. Dept. of Agriculture
In fact, as a furniture maker, there are several "fixes" one can use to deal with wood movement.
- Avoid bad technique like cross grain or "trapped" construction
- Apply finish to all surfaces. It won't stop it, but it will temper the movement.
- Calculate and account for wood movement for the species you're working with.
- Start with lumber that's dried to a moisture content that matches where it will live.
The last one can't be over stated! I've heard the "let it acclimate to the shop" more times than I care to count. Good advice? Hokum? It depends on your shop. It's far better to "let it acclimate to where it will live." My shop isn't environmentally controlled, so building with "dry" wood can be a challenge.
Personally, I find air dried lumber preferable to work with over kiln dried. I think it's easier to work and it looks better. But, I won't work with it until it has been confirmed as being dry with a good moisture meter. To get it to furniture dry, I'll do the following:
- Store it inside until it comes down to 6% - 8% moisture content.
- Never mill or work it until I'm ready to use it.
- Bring it inside or wrap it in plastic wrap (or both) if I can't use it right away.
A Final Thought...
Just give working with wood that's "furniture dry" a try one time. I think you'll like it.
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