Acclimating Wood

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[attachment=38465]I have purchased a number of boards to finish a few projects.  Some of the boards have been in my shop on hand for a long time and are fully acclimated.  The others arrived on Wednesday.  Putting 9 and 10 foot boards on stickers takes up a huge chunk of my shop and makes it hard to get around so I would like to get these milled and the project built ASAP.  The project will be a workbench done butcher block style.

I have a moisture meter, I purchased for sailboat hull inspections with woodworking as a secondary use.  I am getting readings between 7 and 11 percents.  The similar species hard maple and walnut all run within 1-2% of each other from the acclimated boards and newer boards.  Walnut is around 7% and Mape around 11 percent. plus or minus.  If boards are that close can I go ahead and mill it and glue it up?

[fredhargis]

I would, if they've set in the shop since Wednesday I consider them good to go.

[jteneyck]

What's the moisture content of wood that's been in your shop for several months?  I don't use wood until it's within +-2% of wood that's been in my shop.  I definitely would not use woods with a 4% difference in MC in the same project.  

I once bought some wood that turned out to be 12% MC.  I left in my shop for 4 or 5 days then resawed it.  It cupped so badly it was unusable.  That was probably the worst thing I could have done because the surface had dried to 8 or 9% (the same as my shop) but the center was still 12% or more.  If you can't wait for wood to reach equilibrium with your shop it's best to use it immediately while the MC is relatively consistent, plane equal amounts off both sides, and don't lay it flat on your bench between sessions, rather, stand it on edge so air can circulate uniformly around it.  

John

[tablesawtom]

I bought 58 BD FT. of ash at the local saw mill Oct 4th. I really do not see any reason to let it acclimate. It was exposed to the atmosphere there and it will be the same atmosphere in my shop . I started cutting as soon as I got it in my shop. I am building a bench top for a Moravian Work Bench

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I straight lined riped a straight edge using a sled and then I moved it over 4 3/8ths inch and ripped it again using the sled. Usually I rough cut my pieces a little oversize in both length and width. And them hang the wood on a close line after writing the detail number on it. Moisture only effects size. And if a builder allows for it in the build then it does not come into effect. 

 Covering My Bases here, because I am going against the thinking that came from tradition.  And some will jump on this as all wrong,  because they know all about it. But use your head and actually think about what I am writing and just try it once for your self.    If you have a basement shop, the humidity level will be more humid there than the upper levels in the house. So in theory the wood should be acclimated in the room that the piece is going to be in. Good luck with that with the misses.  Which, here in Iowa, will be different in summer verses winter and all places in-between. 

I think that the different stresses effect wood a lot more than moisture ever could. There growing stress from it trying to get sun light,  where it grew, The effects of wind, snow, as well stress imparted to it when it hits the ground after feeling the tree. Then there is sawing stress and drying both air and kiln drying. Not to mention that wood toward the top of the stack during the drying process tends to move around more than the bottom of the pile because of weight. 

My question now is: What difference will it make if you rough cut it mow or after it acclimated ?  The time and work are the same. It took more than one Saturday afternoon to do the work and I got a large part of the mess cleaned up while rough cutting. 

I started to hang my wood on my close line but it didn't take a rocket scientists to figure out the line wasn't going to hang the wood. Luckily I had a copper air nine suspended from the ceiling a little bit so I used it.

By hanging it you allow it to acclimate on all four sides of a piece close to size. If the board is 11 inches wide and you  cut 2 4 3/8ths pieces you still have a piece left over over 2 inches wide ( don't forget what was lost during the straight line rip.

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If a board closed up on itself during a cut it is not moisture that causes it ( moisture effects size ) it is internal stress. Or case hardening during the drying process. Boards move because of internal stresses and by hanging it you allow it to self stress relieve itself.  Out of the 11boards I had 3 boards, that were un-usable for their intended task, but can be used other places so not a complete lose of anything. 

I let it hang for a week before I started working with it. And a lot of times I will then rough mill it to size and then let it set a day or two more. 

I hope some of you forget the wives tail about worrying about moisture.

Tom

[jteneyck]

You may think otherwise, Tom, but wood does move if you cut it when it has a non-uniform MC, especially when you resaw it.  It's not just internal stress that can cause movement such as cupping and bending.  Guys like Bruce Hoadley at the Forest Products Lab spent decades studying this stuff.  Read his book sometime.  

The natural RH in my basement is higher in the Summer than upstairs, and lower in the Winter.  So I run a dehumidifier in the Summer and a humidifier in the Winter to keep them in line.  But that's completely irrelevant if I bring in wood and start using it before it's acclimated to my shop.  The method you described is an effective way to deal with wood that's not at equilibrium with your shop, and similar to how I handle wood that I have to work right away.  

John

[rwe2156]

In my view, acclimation is a relative term, where as moisture content is an absolute.

Acclimation is simply homeostasis with the environmental humidity. The question is "acclimatized to where?" Building a table in Denver is a lot different than south Florida.

7% is perfect, 11% is probably fine, too. Just keep in mind the possibilities of movement after it is in your house.

Mill it in stages, don't get in a hurry. Part of acclimatization is allowing the wood to de-stress, which saves you from a lot of dis-tress :-D

In reference to Tom's post, I think the weight of stacking is a benefit to keep a board from getting to freaky when it acclimates. IOW, I've always thought it a good idea to "hold" lumber while it dries/acclimates. Then again, maybe he's onto something with his "clothes line" ANTIFA method - let the wood freak out and do whatever it wants.

[photobug]

What I find interesting is the boards on sight for a long while in the shop are at 10-12 percent and the new boards are closer to 8% MC.  The corporate office from where I get my wood is in SLC Ut so it is even drier there so it is possible the wood is even drier than normal.

This wood is to be built up to a butcher block for a Ruobo style bench.  If I could mill it flat then cut them to width and mll up the butcher blocks in a day, would the butcher blocks be safe, meaning not likely to split?

[jteneyck]

What I find interesting is the boards on sight for a long while in the shop are at 10-12 percent and the new boards are closer to 8% MC.  The corporate office from where I get my wood is in SLC Ut so it is even drier there so it is possible the wood is even drier than normal.

This wood is to be built up to a butcher block for a Ruobo style bench.  If I could mill it flat then cut them to width and mll up the butcher blocks in a day, would the butcher blocks be safe, meaning not likely to split?

OK, that means the RH in your shop is around 55 - 65%; probably no different than for a lot of folks during many months of the year.  But when you say it's 10 -12% MC are you using pin meter, non contact meter, or weighing and drying a sample?  If you are using a pin meter you are just measuring near the outer surface.  Cut a board in half and measure the end from surface to center.  The average of those values will be the average MC.  The better way is to cut a full width sample at least a foot from the end of a board, weight it, dry it at 220F until the weight is constant, and then calculate the MC.  

The best options are to either let the wood fully acclimate to your shop or use it as soon as you get it home, as Tom described.  Using wood with large gradients in MC almost always turns out badly.  

John

[tablesawtom]

, but wood does move if you cut it when it has a non-uniform MC, especially when you resaw it. Are we talking air dried or Kiln dried. And construction grade is only fast dried to around 15%. And it is a different animal, under different grading scales. Also wood tends to cup with the growth rings The growth rings want to go Straight.  That is why the inside of a drawer side  has to be the outside of the tree so if it cups the corners remain tight. So there is more going on than just moisture content. And if it isn't dry in the middle by the time you get it letting it set for six months isn't going to make a lot of difference. If you re-saw it and let it set for a while and let nature move it where it wants to go, then one can  proceed.

I have been dealing with the sawmill pictures for years and he is not a fly by night operation. Dried the wood to 6 to 8 percent. That means he whole board is that percentage. If it were wetter on the inside than the outside can't get to the required percentage.

I believe I wrote rough cut to size. Cutting growth rings stops the board from wanting to cup as much. Hang it allows it to go to its free state with out outside factors influencing it. Stacking boards on top only slow the process. If a board is going to bow it will do it when you unstack it. Let it move and then finish milling it. 

Tom

[jteneyck]

, but wood does move if you cut it when it has a non-uniform MC, especially when you resaw it. Are we talking air dried or Kiln dried. And construction grade is only fast dried to around 15%. And it is a different animal, under different grading scales. Also wood tends to cup with the growth rings The growth rings want to go Straight.  That is why the inside of a drawer side  has to be the outside of the tree so if it cups the corners remain tight. So there is more going on than just moisture content. And if it isn't dry in the middle by the time you get it letting it set for six months isn't going to make a lot of difference. If you re-saw it and let it set for a while and let nature move it where it wants to go, then one can  proceed.

I have been dealing with the sawmill pictures for years and he is not a fly by night operation. Dried the wood to 6 to 8 percent. That means he whole board is that percentage. If it were wetter on the inside than the outside can't get to the required percentage.

I believe I wrote rough cut to size. Cutting growth rings stops the board from wanting to cup as much. Hang it allows it to go to its free state with out outside factors influencing it. Stacking boards on top only slow the process. If a board is going to bow it will do it when you unstack it. Let it move and then finish milling it. 

Tom

When you dry wood there always is a gradient.  Otherwise, moisture won't move to the surface to be removed.  When wood comes out of a kiln at an average of 6 - 8%, yes, the whole board is 6 - 8%, but the outside will be lower, the inside higher.  If the wood is dense stacked after it's pulled from the kiln the MC will tend to equilibrate within the wood over time except for those on the outside of the stack.  Wrapping the bundle in plastic will allow all boards to come to equilibrium.  

John