Wood Moisture and Acclimation (Midwest)
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8 September 2014 at 12:33 am #66987
Me again. I’m rather new to woodworking and I’m curious about wood moisture. Do I need some kind of moisture meter? Is most rough-sawn green or not green (recently cut)? Assuming it’s not, how long should I expect to let it sit in an unheated, uninsulated, unvented garage before it has “acclimated”? I live in the Midwest in an area with very humid summers (80-95%) and no dry season (lowest humidity is probably 35-40%).
8 September 2014 at 12:51 am #67001A moisture meter is not a bad thing to have, I would think. Having said that, I don’t own one and don’t plan to buy one any time soon.
Any green wood will take 3-4 months or so for 4/4 (1″) thick boards to air dry outside, assuming they are stacked and stickered (spaced with small cross pieces for air circulation) to 20 % moisture or so. If using for furniture in an indoors heated building, this is still not dry enough, as 6-8 % is usually recommended, with 8% often cited as an acceptable avg. in our part of the country (the Midwest U.S.) Depending on where in the midwest you live, the basic avg. equilibrium moisture contend for air-dried wood stored outside is around 12-13%, which is probably close enough for most things.
Ideally, you want to acclimate lumber in the same conditions the finished piece will “live” in when possible. When people talk about acclimating lumber, they usually mean storing already dried lumber in their shop for a couple of weeks to let it come to an equilibrium with the shop conditions.
The fact that lumber is rough sawn really has nothing to do with whether or not it is dry; the two things are really not related at all.
8 September 2014 at 10:34 am #67948Hi Ben,
As already mentioned, a moisture meter is handy. They’re not, however, essential and you can get by with a set of bathroom scales.
Bring the wood into your shop and weigh it straight away. Then weigh it every week until you get a few almost identical readings. At that point, you know the wood is in equilibrium with your shop environment.
Weighing the wood is arguably more reliable than a moisture meter as the moisture meter pins only go 1/8″ or so into the wood. The scales will take the whole board into account.
Again… rough sawn and moisture content are independent. Rough sawn timber can be kiln dried or air dried. I recently picked up a huge slab of yew that the seller had had sitting in his timber shed for around 25 years, and the tree had been felled some time before he acquired it, so it’s pretty well dried despite being rough sawn.
I’m afraid I can’t help with the huge swings in humidity. We don’t get anything like that here in the UK!
George.
8 September 2014 at 1:00 pm #68085That makes some sense.
I’m afraid my “shop” is probably 70-80% right now and at best is probably 35% in March.
So, I’m afraid anything I make that’s for indoors will move quite a bit after being made and living indoors for a few weeks.
I almost wonder if I’ll need a dehumidifier in the garage or something. But those only get the environment down to 40% I think and won’t work in our long winters in an unheated garage.
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