Drying green lumber
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You make it sound so easy.Obviously with me being in the soggy south, this process is going to take a while. 3-6 months sound about right.
It's pretty damn soggy up here, too right now. I do the smell test.....when they don't smell 'pitchy' anymore, I let them dry for about another month if possible. You can speed the process by putting a box fan at one end if you want.
I just did this with a bunch of Elm. Depends on how fast you want to dry it.
I needed to dry it very rapidly as the wood was starting to mold, and we were getting buckets of rain, so leaving it outside was no longer an option.
The fastest way is to make a kiln. For a kiln to be effective, you need a way of removing moisture from the air. I simply used a empty room I had, stickered the wood up (the more spacing you have the better), and put a dehumidifier in the room. Couple of fans to keep the air moving through the wood.
Using a dehumidifier is very quick, but not very cheap. Plus the moisture is very acidic, and corrosive to the dehumidifier. If you're just doing it once, you shouldn't damage anything, but drying wood repeatedly could be a problem. There's been plenty of kilns that had their dehumidifier short out and catch on fire....obviously not a good thing when they're sitting next to a perfectly stacked bonfire!
The more traditional way (if slower) is to basically build a room, heat it up to get the wood to release moisture, then vent that moisture laden air to the outside. Doesn't work very well if it's raining a lot, and can be pretty slow. You have to watch how much air you're moving very carefully as well, if you move too much then it's not effective. Too little, and your wood will just mold.
One of the better ones I've seen is basically a greenhouse with some solar panels powering fans to move the air through the stack of wood. With some small vents in it to exchange air, the sun naturally heats up the interior and will draw moisture out. At night the cool air will allow the wood to reabsorb some of the moisture back in which helps with checking, splitting, and warping. This method is slow (I've read that it can take as long as 6 to 9 months!), but cost free after the initial investment and tends to produce good batches of wood.
What type of wood are you looking to dry and how quickly do you want to dry it? Some types of wood doesn't handle being dried quickly very well. The Elm that I dried had no problems with being dried in just 3 weeks, but Elm is extremely tough wood. Lots of other wood would split or check, not much good if you throw away a quarter of your wood because you have to cut the ends off due to splits.
I needed to dry it very rapidly as the wood was starting to mold, and we were getting buckets of rain, so leaving it outside was no longer an option.
The fastest way is to make a kiln. For a kiln to be effective, you need a way of removing moisture from the air. I simply used a empty room I had, stickered the wood up (the more spacing you have the better), and put a dehumidifier in the room. Couple of fans to keep the air moving through the wood.
Using a dehumidifier is very quick, but not very cheap. Plus the moisture is very acidic, and corrosive to the dehumidifier. If you're just doing it once, you shouldn't damage anything, but drying wood repeatedly could be a problem. There's been plenty of kilns that had their dehumidifier short out and catch on fire....obviously not a good thing when they're sitting next to a perfectly stacked bonfire!
The more traditional way (if slower) is to basically build a room, heat it up to get the wood to release moisture, then vent that moisture laden air to the outside. Doesn't work very well if it's raining a lot, and can be pretty slow. You have to watch how much air you're moving very carefully as well, if you move too much then it's not effective. Too little, and your wood will just mold.
One of the better ones I've seen is basically a greenhouse with some solar panels powering fans to move the air through the stack of wood. With some small vents in it to exchange air, the sun naturally heats up the interior and will draw moisture out. At night the cool air will allow the wood to reabsorb some of the moisture back in which helps with checking, splitting, and warping. This method is slow (I've read that it can take as long as 6 to 9 months!), but cost free after the initial investment and tends to produce good batches of wood.
What type of wood are you looking to dry and how quickly do you want to dry it? Some types of wood doesn't handle being dried quickly very well. The Elm that I dried had no problems with being dried in just 3 weeks, but Elm is extremely tough wood. Lots of other wood would split or check, not much good if you throw away a quarter of your wood because you have to cut the ends off due to splits.
I usually let our woods air dry for over a year, 1.25-1.50 inches thick. MIke
You might want to pick up a moister meter to see how well it has dried out before you use it.
That's actually not the best way to do it.
The ideal way is to take a board from the middle of the stack. Cut two 1" long strips from the middle of it. Bake one of those strips, you can use the microwave (do it in short 1 or 2 minute bursts to prevent overheating the wood) or an oven for several hours at around 150* or so. Keep drying it until when you weigh the wood the weight doesn't drop anymore.
Compare that weight to your 1" strip you didn't dry. The difference is how much moisture content is in the wood.
You can do it with a board from the top of the stack and cut off an end piece, but it's not as accurate (since the top and ends will dry faster than a board in the middle, and the middle of the board).
A MC meter will have trouble accurately measuring the MC in the wood once you get down to the lower percentages.
Also, you can over dry the wood. After you've baked the moisture out of it, let it sit for at least a week (longer is better) in the environment where it will be used. That way it can reabsorb some of the ambient moisture and will be less likely to warp once it's installed. If a piece of wood is very dry (say single digits MC) and installed where the wood has a higher level of MC (such as outside), then the wood will change as it reabsorbs moisture.
I airdried a whole bunch of green ash a few years back. The loca portable swamill guy cut it into 1" + slabs. I stacked it behind the shop, stickered with lath and covered with a lid of plywood, for about 18 months. The rule of thumb up here seems to be one year per inch thickness.
Now its stacked in the shop waiting for my kitchen project.
Now its stacked in the shop waiting for my kitchen project.