I was asked to make a jewelry box out of the wood from our land a few weeks ago. I split some oak and let it dry as much as possible in the small frame of time. Tonight, I planed and squared the boards. They are still awfully wet. I intent to make the joints on the sides with a dovetail jig. The box will sit on a decorative base cut on a band saw. And the lid will be a mortise and tenon frame with an unglued panel in a groove.
What's going to happen when I complete the project? Will it eventualy split and/or warp?
General rule for air drying lumber is approximately one year for each inch of thickness. This assumes proper stickering and air circulation over your stack of lumber.
If you can get the moisture content of your wood below 15% it should be stable enough to get your jewelry box assembled. Ho long it stays assembled is directly related to how dry you can get the lumber.
General rules, as you will easily see, are more folklore than fact. They apply to "seasoning" of wood outdoors, and presume use in a non-dehumidified environment. Air conditioning and central heating both lower the relative humidity.
If you have material to spare, and I would suppose you do, you can try drying in both a microwave and a conventional oven. Weight eh pieces on a kitchen scale and weigh them periodically while drying. When the weight stops changing, they're done. The same is true for air drying.
In a conventional oven trelatively hin pieces will dry overnight at 150 F or so. It may be best to dry overnight at the lowest setting and the next night a little higher and so on until stable.
In a microwave, use several short burst of no more than a minute or so, and allow a couple of minutes between them for the wood to equilibrate.
Both methods may warp the wood, but you may get lucky.
It may be possible to flatten warped wood using the same methods used to bend straight wood (steaming, soaking or boiling). Google "wood bending", "bent wood" etc for more information.
Red oak will stink. If you have Sassafrass, drying it in the oven has a deoderizing effect. One of managers at work (or his wife) accidentally left roast in their oven baking all day. By the time he got home it was coked out and the next day he said his whole house smelled terrible. So I wnet home at lunchtime and brought back a small Sassaffrass log, gave it to him and told him to bake it at 150 F overnight. He looked at me like I was crazy, but he tried it and was amazed at how effective it was.
I bought a moisture meter (Lignomat Moisture Meter Mini-Ligno E/D)--works great. I test each plank in three spots and write the highest reading on the wood with the date. If the reading is above
10%, I put it back on a stickered stack for 2 months. A reading above
15% will take several months to air dry. Don't waste your time building furniture with anything above 10%.
Anybody ever tried vacuum drying? I have some small pieces that will fit in a 30" cube vacuum chamber that a friend found for me at a surplus sale. The unit will pump down below the usual level for AC systems, about 150 microns or so. Might make for some low temp stress free drying.
It has been done (basically one has to consider the chamber to have
100% relative humidity and the pressure in the chamber is the variable), just as kiln drying (with mild heat). The usual problem is control of the drying rate (you might want to do one day in the chamber,
6 days out, for several cycles). Some vacuum pumps don't do well with water vapor (oil turns to sludge).
If it dries too fast, checking and excessive warp/twist is expected. The USDA wood handbook hints that 2" oak needs about 50 days to kiln dry, and the temperature of the kiln would be circa 120 to 180 Fahrenheit.
It has been done (basically one has to consider the chamber to have
100% relative humidity and the pressure in the chamber is the variable), just as kiln drying (with mild heat). The usual problem is control of the drying rate (you might want to do one day in the chamber,
6 days out, for several cycles). Some vacuum pumps don't do well with water vapor (oil turns to sludge).
If it dries too fast, checking and excessive warp/twist is expected. The USDA wood handbook hints that 2" oak needs about 50 days to kiln dry, and the temperature of the kiln would be circa 120 to 180 Fahrenheit.
Vacuum kilns are available commercially for small lots. Of course 100% humidity would never dry, so you have the same problem as the standard kiln operator who excites his molecules with heat rather than providing less pressure - getting the humidity down.
Can't exhaust it as produced as he can, so you have to set your cycles to get rid of the stuff through air traps or times of no vacuum.
As Lobashevsky said, "let no one's work evade your eyes" and check out the schedules and mechanisms the big guys use. Reinvention would be tougher.
The vacuum pump on my system has a 'gas ballast' pump, commonly used in laboratories, which admits a bit of clean air in the last bit of the pump rotation to sweep out trapped gases. This keeps the pump oil useable for some time in my experience. Maybe the limiting factor will be the transpiration rate of the moisture through the wood. Logically, then one could pull the pressure down in steps over a period of hours (?) or whatever, and let the system finally equilibrate at full vacuum, then allow the pressure to reach ambient. Might try that and report back in a few weeks. Thanks for comments.
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