Waiting Before Milling Wood

[John Stevens]

I've always read that when you buy "fully dried" wood, you should let it sit in your workshop a few weeks before you begin face-planing, jointing and thickness-planing it. The reason I've read is that it's best to allow the moisture content of the wood to come to a new equillibrium. Makes sense generally, but aren't there situations when the moisture content won't change? For example--

Last week, I bought some rough 4/4 maple that was kept dry in a barn at a sawmill for a few weeks after being kiln dried. No air conditioning in the barn, and plenty of airflow. The barn is only 35 miles away from my house, so there's no difference in climate between the two locations. The lumber is now sitting in my house, which has no air conditioning or heating this time of year, and plenty of airflow through the open windows. Yet I'm still letting it sit for a week before I begin milling it.

How dumb is that?

[Jeff Sudmeier]

John, it's not dumb at all, if you have the time it is always best to let it acclimate.

That said, I get all timber from a guy 15 mins from my house and I start milling it the same day (about 10 mins after getting home) as I buy it.

[Byron Trantham]

I have a moisture meter and I test the "new stuff" against my existing stuff and usually they are very close so I go for it. I had one case where there was a measurable difference so I let it catch up with known material in my shop. Took about a week.

[John Miliunas]

How dumb is that?

John, I don't think "dumb" is it, but rather, "good practice". Look at it this way: It certainly won't hurt!:) Now, when presented with a similar situation, and please don't take this as gospel, what I do is: If I feel the wood is already close to equilibrium (taking a MC reading), I won't wait a couple weeks. Instead, I'll go ahead and start processing the material BUT, I do NOT complete the process. What I'll do is, for instance, face & edge joint one side each, then go ahead and plane the material, but only to within about 1/16 to 1/32" of the final thickness. Then, I put the material aside for 2 or 3 days and allow it to "rest". Often, the milling process will release certain stress of the wood, as well as get closer to where more moisture may still dwell. Once uncovered, as it were, the stabilizing of said material becomes much quicker. Be aware that additional cupping or general distortion may also rear its ugly head!!! BUT, that's why you leave yourself some "fudge factor" in not planing to final thickness.:) NOT an expert, but I've had good results using the above procedure.:) :cool:

[lou sansone]

John, I don't think "dumb" is it, but rather, "good practice". Look at it this way: It certainly won't hurt!:) Now, when presented with a similar situation, and please don't take this as gospel, what I do is: If I feel the wood is already close to equilibrium (taking a MC reading), I won't wait a couple weeks. Instead, I'll go ahead and start processing the material BUT, I do NOT complete the process. What I'll do is, for instance, face & edge joint one side each, then go ahead and plane the material, but only to within about 1/16 to 1/32" of the final thickness. Then, I put the material aside for 2 or 3 days and allow it to "rest". Often, the milling process will release certain stress of the wood, as well as get closer to where more moisture may still dwell. Once uncovered, as it were, the stabilizing of said material becomes much quicker. Be aware that additional cupping or general distortion may also rear its ugly head!!! BUT, that's why you leave yourself some "fudge factor" in not planing to final thickness.:) NOT an expert, but I've had good results using the above procedure.:) :cool:

I definitly agree with john on this one. most of my wood has been sitting in my shop for few years ( I do add new stuff once a year - and I need to sell some to make room for the next load ). I still do as john said in his post. once you start processing the wood it can seem to move. The other thing I like to do is keep the pile I am working on semi-covered, so the top board does not start to get drier than the rest of the pile ( this is in the case of resawing, which I have been doing a lot of for thin stock ).

lou

[Alan Turner]

John,
If you have the time, a resting period is a good general procedure. It can't hurt. Let it sit a bit, and then rough mill the stock, and let it sit a second time. Then go for it. If you have time, this procedure will give you a greater chance of no stock movement after final milling. Nothing is more frustrating that doing the milling to final dimension, and finding movement. 4 square stock is step one, and a necessary one, to a good piece.

[Scott Parks]

I don't think it is dumb either. However my wife does, because I'll bring home lumber and put it in the living room for a week before I use it.

I had an ooops peice of 3/4 maple laying around my garage that had been finished and sealed about 1 1/2 years ago. I ripped off about 1" recently and couldn't beleive how much it twisted after I cut it off!:eek: I can't explain that one...

[Kirk (KC) Constable]

I don't go out of my way to acclimate, because as soon as it's milled, built, and finished in the shop environment, I'm moving it into the house...where it's air conditioned. Perhaps I just don't get it...

[Tim Sproul]

I've always read that when you buy "fully dried" wood, you should let it sit in your workshop a few weeks before you begin face-planing, jointing and thickness-planing it. The reason I've read is that it's best to allow the moisture content of the wood to come to a new equillibrium.

Techinically speaking, it isn't a problem for wood to be at a different moisture content than what the shop humidity dictates is the EMC. The problem arises when a single board has an asymmetric gradient in moisture. I will put forth that in real world situations, no stick of lumber is at a uniform, constant moisture content throughout the entire stick. The problem arises mainly when one face has higher moisture than the other....such as when one lays a board on a flat surface and the humidity switches from 40% to 70% overnight. You'll likely find that board/panel cupped with the crown up.

IME, acclimation is most critical when resawing thicker boards because this tends to lead to assymetric moisture gradients in the resawn boards. Almost always, a board will have more or less moisture in the middle compared to the surfaces. Resaw it in half and the bookmatched faces will then have more or less moisture than their opposite faces...leading to warp.

The symmetric moisture gradient in a board is the reason why you should remove approximately the same amount of material from either face when thickness planing...and also why boards move a bit when you rip a 6 inch board into 2 inch boards.

So, if you don't plan on ripping the lumber beyond the minimum needed to get to 4 square and you won't resaw, use lumber as you get it. If you need to do either of those, I'd suggest you acclimate your lumber as long as you can.

As far as moisture changes once a piece is completed....that isn't such a problem. The design/engineering and joinery keep mild amounts of warp in check until the lumber has a chance to equalize moisture content.

[Jim Becker]

I go so far as to use thin (1/4") stickers between "dry" stock in my shop to help insure that there is some air circulation all the time. It's not "necessary", but I find it to be yet another good hedge. I also agree with John that letting a bit of acclimation to occur is a good thing. In fact, it's not a horrible idea to allow a board to set overnight after milling it "most of the way, but not all the way" so that the moisture differential between the newly exposed surfaces and the middle of the board has a chance to get happy. I do acclimate boards from a supplier no matter how dry they happen to be and check with a moisture meter to hopefully choose stock for a project that is close to the same MC in addition to being of appropriately matched grain and color.

[Tom Andersen]

Last week, I bought some rough 4/4 maple that was kept dry in a barn at a sawmill for a few weeks after being kiln dried. No air conditioning in the barn, and plenty of airflow.

That confuses me a little. When you kiln dry wood, you typically get the MC down to 6-8%. If you then move it to an unheated barn, depending on the climate, I would assume that the MC goes up to 12-14%. Shouldn't kiln dried wood be taken to a heated room or, at least, be wrapped in sealed plastic foil?

[Ian Abraham]

That confuses me a little. When you kiln dry wood, you typically get the MC down to 6-8%. If you then move it to an unheated barn, depending on the climate, I would assume that the MC goes up to 12-14%. Shouldn't kiln dried wood be taken to a heated room or, at least, be wrapped in sealed plastic foil?

In an ideal world.. yes

Back in the real world it doesn't happen, hence the advice of letting your wood acclimatise. You are talking about small variations +/- 2% like occurs natually with the seasons. But if you get wood dried to 8% and take it to a 12% shed, let is sit for a couple of days, then rip in in 1/2. It's going to move a little. If you let it sit for a couple of weeks then it will be even thoughout and less of a problem. Then once it's made into furniture hopefuly you have accounted for a little seasonal movement in the design and all is well.

Anyway, many evils can be avoided by letting a board sit for a few weeks ;)

Cheers

Ian

[Michael Gabbay]

I'm pretty AR about letting my wood acclimate. I usually store my bulk stuff in the garage and the materials for a project in my basement shop. The basement is cliamate controled and has a dehumidifier. I let it sit stickered for at least 2 weeks in the shop. When I start milling I do my rough sizing and jointing and let it sit stickered for a 3 - 5 days and then plane it. I have found that when I do it like this I rarely have any movement/warpage after my final milling.

I have a walnut table project that has been milled and sitting stickered for the past 9 months. All of the pieces are still the way they were when I first milled them. Now when I go home tonight and check it they will all be warped! :eek: :D

Since I'm a hobbiest I can stand to wait a few extra days to let the wood settle.

Mike

[John Stevens]

I don't think it is dumb either. However my wife does, because I'll bring home lumber and put it in the living room for a week before I use it.

Heh heh, my wife suffers from a similar problem, because I store the lumber in the dining room. However, she doesn't mind...maybe because we're also storing a tandem and single bicycle there, so the room already looks like a barn.

Thanks to John M., Lou, Alan, Jim and Michael for endorsing the idea of rough planing, then letting the wood sit a little longer. I'd thought about that, but figured I was being a little too "compulsive" because I couldn't remember seeing it in a WW book. But if you guys are doing it....

Thanks also to Tim for the in-depth explanation of symmetrical vs asymmetrical moisture gradient in lumber. That will definitely help me make practical decisions in the future.