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post #1 of 15 Old 02-12-2013, 08:46 AM Thread Starter
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Acclimating wood moisture question

I keep reading that after I kiln dry my wood that I should let it acclimate in my shop. Right now my shop is half of my garage and the other half is where I park my truck. On snowy days it can sometimes get kind of damp and after leaving the wood exposed for a few days it went from 6 % to some was up to 18%. Does this seem normal? The wood is 2 inch maple.
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post #2 of 15 Old 02-12-2013, 09:40 AM
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Here's a case where shop wisdom is propagated in these one-sentence chunks with no background. The wise practice of letting wood acclimate in the shop sort of assumes that the shop environment would be similar to the environment where the final piece would live.

For just a little more, you can do it yourself.
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post #3 of 15 Old 02-12-2013, 09:52 AM Thread Starter
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I understand that you want it to acclimate to its final destination. My shop however is my garage which is for the most part fairly dry but right now we are having rainy snowy weather and its sort of damp right now. I guess my question is what do other guys do with shops out of their garages in these cases?
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post #4 of 15 Old 02-12-2013, 10:56 AM
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I guess what I would consider doing if my shop had much damper conditions than where the piece was going would be to store the raw materials in the drier location for a few weeks, and if building were a long term effort, try to bring it into the conditioned space when possible.

Moisture transfer is a pretty slow process, so exposure to the damper conditions for a few hours or maybe even a few days might not be a big problem.

For just a little more, you can do it yourself.

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post #5 of 15 Old 02-12-2013, 12:14 PM
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I have never paid much attention to that. Typically in my shop which is not conditioned if I am not there, moisture levels in lumber can go up to 12%, while in most conditioned houses it can go as low as 6%.

When I build, I allow for that, rule of thumb is 1/4" for 12" width., or 1/8" shrinkage and 1/8" expansion.

Irrespective of the above, if you build a piece and move to the Gulf coast in Florida and then again move to Arizona, the piece has to survive, without cracking.
The finish won't help you, it may slow things down a bit, but not enough.

Pure mathematics is, in it's way, the poetry of logical ideas. - Albert Einstein.

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post #6 of 15 Old 02-12-2013, 12:19 PM Thread Starter
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Ok well this is a mirror that I am making. How do i compensate on shrinkage on something like this?

Acclimating wood moisture question-image-2236757473.jpg
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post #7 of 15 Old 02-12-2013, 12:39 PM
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Quote:
Originally Posted by tdoucette67 View Post
Ok well this is a mirror that I am making. How do i compensate on shrinkage on something like this?

Attachment 62616
The miters don't really look wide enough to cause any issues. Expansion is across the grain, not in the length of the grain. Worst that could happen is that your miters open up ever so slightly.

How are you planning to fix the mirror to the frame?

Pure mathematics is, in it's way, the poetry of logical ideas. - Albert Einstein.
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post #8 of 15 Old 02-12-2013, 01:35 PM Thread Starter
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Before I glue it together I'm going to make a groove on the back for the mirror to slide in.
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post #9 of 15 Old 02-12-2013, 01:42 PM Thread Starter
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Before I glue it together I'm going to groove out the back for the mirror to slide in.
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post #10 of 15 Old 02-12-2013, 02:09 PM
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If you alow a little room between the mirror edges and frame, and reinforce the miters, I think you'll be OK.

For just a little more, you can do it yourself.
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post #11 of 15 Old 02-12-2013, 08:41 PM Thread Starter
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So I ended up checking a piece of scrap that I cut off before I started. The piece hadn't been planed down yet and the MC was still below 10%. It turns out the damp garage wasn't the problem. I'm thinking that the wood that I'm using wasn't all the way dry on the inside. My meter said it goes down 2 inches but I'm not sure if it does. After I planed the board down a little the MC was at 20% toward the middle. Could this mean the wood is case hardened?
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post #12 of 15 Old 02-12-2013, 09:25 PM
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Quote:
Originally Posted by tdoucette67 View Post
So I ended up checking a piece of scrap that I cut off before I started. The piece hadn't been planed down yet and the MC was still below 10%. It turns out the damp garage wasn't the problem. I'm thinking that the wood that I'm using wasn't all the way dry on the inside. My meter said it goes down 2 inches but I'm not sure if it does. After I planed the board down a little the MC was at 20% toward the middle. Could this mean the wood is case hardened?
Theoretically maybe but 20% is about at moist a board can get and not have free water(be wet). Your meter is off or the wood is nowhere near "dry".
Air dried wood or wood equilibrated to about 70% humidity will be near 12%. You want to at least get to this level with rare exceptions like some parts of chair constructions.
If you had to work in and outdoor environment, you would need to pick your projects, plans carefully.
Lap joints in frames would be wiser than wide mitered joints etc. You can/must, as mentioned, plan for later changes and allow for them.
The expected movement can be predicted and calculated for.
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post #13 of 15 Old 02-12-2013, 09:34 PM Thread Starter
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Yeah I think my meter is fine. The wood is definitely not "dry" enough yet so I put it all back in the kiln. I really can't use a lap joint either because I'm trying to leave a live edge all around the frame.
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post #14 of 15 Old 02-12-2013, 10:16 PM
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What is the wood you are using?
Softwood coefficients are smaller than hardwoods. The opening of a miter is dependant on the width of the boards, the change in moisture content and the amount the type of wood used moves for a given change. Softwoods like juniper move much less than a hardwood like red oak.
Most of the openings in frame mitres is not noticed at the distances from which they are commonly viewed. It will probably look fine. "live edges" tend to be more "rustic".
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post #15 of 15 Old 02-13-2013, 06:46 AM Thread Starter
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The wood I'm using is maple and the widths are around 5 inches.
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