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Old 25th December 2003, 06:28 PM   #1
eStatic is offline eStatic  United States
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Default Purchasing wood and water.

I don't mean to belabor this, but I do sometimes see things here that concern me regarding the use of real wood.

In my area the target for wood moisture content is 7.5% if the wood is to be used in a typical home. In the desert southwest, 4.0% is considered desirable. Just so you know how important this is, an organ builder, a little north of here, added extra dehumidifiers to his already humidity-controlled shop so he could be confident of delivering and instrument to that area that would last under those conditions. He saws and kiln dries his own lumber so obtaining wood at 4.0% was not the problem. The problem was just keeping it there during manufacture.

In general you cannot trust your supplier to provide wood that is within an acceptable range. My experience with places like Lowes has been that less than 20% of their stock, advertised as kiln dried, is even close to 7.5%. Much is 12% (equilibrium moisture content, EMC, for this area) and not infrequently I find > 20%. I always take my moisture meter when purchasing wood and go over most of the stacks. I do this at Lowes, I think, just to be appalled. In this area you can be fairly confident that soft woods dried to EMC, at the least, will develop serious cracks during their first winter of indoor use.

BTW If you have access to a reasonably accurate scale and an oven you can determine the moisture content without a meter. But, uh, it's a bit awkward to do before you buy.

eStatic.
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Old 25th December 2003, 06:37 PM   #2
eStatic is offline eStatic  United States
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Need to clarify: 7.5% is typical indoor EMC here, 12.5% is typical exterior EMC.

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Old 26th December 2003, 02:33 AM   #3
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I have been woodworking for many years and have never purchased a single splinter of wood without knowing it's moisture content. For serious woodworkers, a moisture meter is a must. I purchase all my stock in the rough and once I know it's moisture content I seal the ends with woodworkers wax to prevent splitting if the moisture content drops too low. I also do not purchase hardwoods from Lowes for Home Depot because they simply do not have the quality of stock that a hardwood supplier can offer and I prefer to surface my own stock because I do not trust S4S to be flat parallel and square. These are some of the caveats woodworkers have to live by. Wood is porus and that is a fact of life we must live with.

My web site: www.woodworkersweb.com
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Old 26th December 2003, 02:59 AM   #4
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eStatic or kWski,

Could you post a photo of a mosture meter for wood? How much would something like that cost?

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Old 26th December 2003, 03:02 AM   #5
hacknet is offline hacknet  Singapore
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is high humidity good?

over here in singapore we are looking at 90% humidity...
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Old 26th December 2003, 04:01 AM   #6
eStatic is offline eStatic  United States
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The ball park range in cost is $60.00 to $300. There are two different types. Probe and R.F. I prefer the R.F. because my suppliers are often a bit reluctant to let me at the more expensive woods with a probe type. Neither is perfect and both have advantages and disadvantages. I check the calibration of mine with a scale every few years.

I'll look for some pictures. Their appearance can vary considerably from brand to brand.

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Old 26th December 2003, 04:06 AM   #7
eStatic is offline eStatic  United States
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Quote:
Originally posted by hacknet
is high humidity good?

over here in singapore we are looking at 90% humidity...

The problem of high humidity is in wood selection. Teak is favored under those conditions for longevity. I doubt that's a real concern for speakers. Other than rot in high humidity it is the variation of humidity, not its absolute value that is the problem for real wood. So, I doubt you have any more problem then those of use in the southeast US, possibly less.

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Old 26th December 2003, 04:21 AM   #8
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In the case of most DIY'ers wouldn't the prudent act be to bring the wood into the house for some length of time so it could acclimate? Once so, sealing it would be enough, right?
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Old 26th December 2003, 09:44 AM   #9
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Rodd,

I have the Delmhorst J2000 which is the digital version of the meter pictured. It reads from 6% to 30% using the probes mounted on the top left hand side of the unit. You can insert the probes up to 5/16ths deep and the unit can test stock to 6/4 (1.5") in thickness. They also make an external probe that connects to the connector on the upper right hand side that will help you probe very hard woods (never had to use it yet). They are available for a couple hundred bucks and are worth their weight in gold to any woodworker.

Click the image to open in full size.
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Old 26th December 2003, 09:56 AM   #10
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Tim,

Absolutely! The reason for this is shrinkage. Wood expands and contracts with moisture content which can be drawn from the humidity in it's environment. You want to work with the material after it has acclimated to the humidity of the environment to which it has been introduced. On my woodworking website I have a shrinkage calculator called the Shrinkulator at http://www.woodworkersweb.com/woodcalc.htm which will calculate shrinkage or expansion for a specific change in moisture content.

PS for a Shameless Plug: Pictures of my woodshop can be found by clicking on "Michele and Guy's Woodshop" in the main menu.
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