Buck the Establishment: Wood Acclimation

wood acclimation

As most of you know by now, I enjoy tilting at windmills , think back to my “Don’t Use Push Sticks or Pads” blog. (I hesitate to link to that post, but I stand by that post , and I love comments that call me a moron.) Established “rules” drive me nuts. And they find ways to, or give excuses for, slowing work. I’m up on a soapbox today about wood acclimation, that is, giving the lumber time to acclimate to your shop before you put it to use.

According to the rules, if you don’t allow your lumber time to get use to its new surroundings, you’ll experience warp and twist to an extreme magnitude. Bull.

Here’s my story. Last Friday we picked up lumber from a woodworker in Lebanon, Ohio, a town just north of the Popular Woodworking Magazine (PWM) shop by about 20 miles. I needed some 4/4 walnut.

We brought some walnut back to the shop and dropped off a portion. The remaining lumber was left covered from the elements in the back of my truck then moved another 20 miles east to my driveway where it sat overnight.

The next morning I drove to my shop (a modest three-mile trek), pulled the wood from the bed of the truck, milled and assembled enough material for two side panels of the chest then went about other chores while the glue dried. Out of the clamps, the panels lay flat. I worked on the bottom-to-sides dovetails. No movement. Before I completed the joinery work on the second panel, I stopped and milled the boards for the case bottom, of which the front edge was the newly purchased walnut mated to fully acclimated poplar. (I live life on the edge.)

The panels remained in the shop for the balance of the weekend while I worked on router-based inlay patterns for the upcoming class. There was no movement. Believe it or not, I was hoping that the panels would warp so I could show the class that all is not lost if this happens to your boards. But there was nothing.

Was I lucky? I think not. What I do think is this: First, the lumber was properly dried to begin with. If hardwood comes into your shop at 22 percent moisture, it’s going to take months before you’re able to use it. Don’t buy it. One of my biggest pet peeves is woodworkers who try to save money by using cheapo lumber on a project that they are willing to spend weeks (if not months) building , projects that will be around for generations to see and enjoy. Why cut corners with the wood? Buy quality and buy from a respected dealer. Second, if lumber is moved from a close proximity to where it will be worked, there is no severe change in the elements. Therefore, there is no need for acclimation. No excuses. Get to work.

Also, use proper milling procedures. As you peel off layers of the boards to bring the wood to square and flat, make sure you take equal amounts , as equal as you can get , off both faces. Mill everything off one face to expose areas of differing moisture content and you’re sure to bend the board. Technique is key.

There are certain instances where this so-called rule stands. Construction lumber purchased from a home store is pulled from the kiln with the moisture content anywhere from 20 – 25 percent. As you know, there have been many benches built in the PWM shop using construction lumber. Take construction lumber from rough to panel in a quick day and you’re asking for trouble. This lumber should be purchased well in advance of when you’ll cut into it and allowed to acclimate. In fact, if you can break down the rough stock into pieces that are oversized in length and width, the reduction in moisture is quicker.

The bottom line is to understand your lumber and how you intend to use it, and follow proper techniques. Sorry about this , you’ll have to think for yourself. Don’t follow some ill-conceived woodworking axiom that begins with the word “always” , as in “always let your wood acclimate to your shop.”

Did I touch a nerve? Let me hear your thoughts. Leave me a comment.

– Glen D. Huey

  • Read “Why Wood Warps” from the Summer 2009 Woodworking Magazine, available here.
  • Click here for information about Chester County Furniture at the Chester County Museum.

 

15 thoughts on “Buck the Establishment: Wood Acclimation

  1. Glen

    Julie,

    It’s now been more than a week and the panels are still flat. In fact, tomorrow I’ll install them into a Chester county chest which I’m building as I teach the class at Acanthus workshop, in Pennsylvania. Ten hours from home and the panels remain flat. Properly dried lumber is well worth the investment.

  2. Julie

    So, because YOUR wood didn’t warp in all of 3 or 4 days, you figure it won’t, so you didn’t need to worry?

    I won’t call you a moron, because I don’t want to make your day.

  3. Jim Stack

    Chris B.,
    There is a difference in the way air-dried and kiln-dried lumber work under your tools, but they will both work together and enjoy each other. If you build musical instruments like I do, you want air-dried lumber. It has better acoustical properties. Some folks have disagreed with me, but my ears tell me I’m right.

    And Jim W.,
    I agree that Glen is a moron, but he’s our special moron.

    Jim Stack

  4. jim welch

    Glen your a moron, (just wanted to make your day also)

    I have a property maintenace company. Two rules never say always, and I have seen everything.

    Thanks for the advice, Jim Welch

  5. Kent

    Although in general I agree with your comments and work in this manner, I have over the last 30 years had a couple of spectacular disasters that can only be attributed to not letting things settle down.

  6. Chris Baer

    Glen, you’re a moron. 😉 (Just wanted to make your day!)

    Kidding aside, do you feel the same about air-dried as kiln-dried lumber? (You didn’t mention in your post ‘how’ the walnut was dried, just that it was done properly) Is there an easy way to tell if lumber has been dried ‘properly’?

    Thanks!

    Chris

  7. matt stern

    Glen, thanks for posting this. I agree, it’s what’s "behind" the rule that counts.

    I’m glad you also explained about taking equal amounts off both sides to minimize warp due to uneven release of stress.

    Keep up the great work!

  8. aaron

    maybe you should rename your post "always let your wood acclimate, but know what that means."

    seems to me your wood didn’t shift because it was properly dried and didn’t experience any significant climate change as the locations the wood was moved from were all in close proximity. if you had subjected the wood to major climate shifts, it would have changed shape, that’s what wood does obviously.

    i agree with your final paragraph about understanding your lumber before you use it, buying properly dried wood (even if price goes up a bit), and not delaying work with needless rules-of-thumb… i just don’t see anything in your post that says "not to acclimate your wood", only that it may be ready to use sooner than you think.

  9. Glen

    Geoff & Bruce,
    As I wrote in the post, construction lumber is different. Air-dried lumber should become stable at the 10% to 12% area, but being that construction lumber comes in at the 20% to 25% area when pulled from the kilns, I would give the stash time to adjust – not so much time to acclimate as it would be to dry and stabilize. But I’m no master when bench building is the topic.

  10. Bruce Jackson

    Geoff,

    You sound like you’re down in Florda, not far from my garage shop, which will some day be A/C’d, if I could figure out how to set up some kind of secondary garage door to let in natual light. But one can dream …

    Anyway, a Nicholson-like workbench made of SYP from Lowe’s is in the cards for me as a fall project, as soon as the garage looks more like the animal it should be and lots less like the attic many of my (our?) neighbors have turned them into. It seems to me that your choice of construction-grade lumber should be fine for our heat and humidity, especially humidity. Who knows, I just may wind up with something lots simpler … surplus P-51 props shanghaied into fan duty.

    Let’s see what the master says …

  11. Eric R

    You are right on the money abut making sure to try & take an equal amount off opposing faces.
    And if your material isn’t coming from some far off climate,you’ll be fine.
    Thanks Glen.

  12. Geoff

    I don’t really let lumber acclimate to my shop that much. My shop is in my garage which isn’t air conditioned so the longer I let it sit there, the more moisture it’ll take on from our humid environment.

    My question is…I plan to build a new bench with contruction lumber as Chris S. has done many times. Since my shop isn’t conditioned do I have to let the construction lumber acclimate?

  13. Steve

    I’m a big proponent of letting the wood "talk to me" regarding how much I should wait for it to settle down. I recently rough-milled up a large quantity of cherry for some chairs. The main planks were 8/4 thick and 18-20" wide, but as I cut it, I didn’t notice much in the way of built-in stresses in the wood, certainly on the low side for planks that wide and thick. Some other planks were 6/4 thick and very curly. When I resawed pieces for bookmatching from that plank, they cupped noticeably towards the cut.

    My (educated) guess was that the pieces from the 8/4 planks would hardly move at all, and that the pieces from the 6/4 planks would likely relax a bit more. As it turns out, I wasn’t able to get back to the project for a couple of weeks, and when I did, I found just what I had expected: I could have used the pieces from the 8/4 plank directly, without even a finishing pass on the jointer, but some of the pieces from the 6/4 plank had moved quite a bit and definitely needed to be rejointed and planed.

  14. Rob Millard

    Glen,

    I couldn’t agree more. The key is proper drying at the mill. I have successfully used lumber that has sat around my garage for years, right along side pieces literally taken off the truck and milled within an hour. In addition to that, my shop and most others are hardly stable as far as climatic conditions go, making acclimation a moving target. Right now it is somewhat like a jungle out in the shop, but in a few weeks or even days, the humidity could be much lower (I doubt it could go higher!).
    Rob Millard

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