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Lumber moisture measurement?

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Forum topic by wiwildcat posted 12-09-2013 03:03 PM 1132 views 0 times favorited 20 replies Add to Favorites Watch
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wiwildcat

58 posts in 1429 days


12-09-2013 03:03 PM

Topic tags/keywords: lumber moisture wood moisture

I have read that lumber should have a low moisture content (6-8%) before milling. This is to minimize wood movement once the project is completed. How does one measure the moisture content without an electronic moisture meter? How did woodworkers do this over a hundred years ago? I would guess that our woodworker ancesters would split and rough mill lumber while green, but did they dry it after that step when using the wood for furniture? I would rather not purchase a meter without investigating other means to accomplish this.

-- Wisconsin Wildcat


20 replies so far

View HerbC's profile

HerbC

1592 posts in 2326 days


#1 posted 12-09-2013 05:58 PM

You can use the Oven-Drying method to calculate moisture content. Oregon State University has a good document available that describes the method.

Good Luck!

Be Careful!

Herb

-- Herb, Florida - Here's why I close most messages with "Be Careful!" http://lumberjocks.com/HerbC/blog/17090

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pintodeluxe

4859 posts in 2280 days


#2 posted 12-09-2013 07:28 PM

A hundred years ago predates forced air heating systems. There was no concern for M.C. except that lumber be air dried or “seasoned” to approximately 15%.

In a climate controlled environment the 6-8% M.C. becomes important.

Even if you don’t have a kiln, you can air dry lumber stacked and stickered outdoors. Once it has equalized (14-15% in the Pacific NW) you can bring it inside to dry the rest of the way. If there is evidence of insects, make sure to kiln dry.

You can get a cheap moisture meter for $20.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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dbray45

3187 posts in 2244 days


#3 posted 12-09-2013 07:28 PM

Much to the work done over a hundred years ago was green lumber. For pieces that required dry lumber, they air dry it outside for a year or two (white oak takes longer) and then put it in the attic for a summer – not insulated.

Keep in mind that kiln dried lumber is harder and more brittle compared to green, which is easy to work. The skill sets for working green lumber are hard to find anymore and takes the trade to a different level than many people want to go – almost a lost art.

-- David in Damascus, MD

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GOOD LUCK TO ALL

418 posts in 1195 days


#4 posted 12-09-2013 07:40 PM

If you don’t want to get a moisture meter, just get your tongue good and wet and stick it against the wood. Pull it away and count how long it takes the wet spot to evaporate. The dryer the wood the quicker it evaporates. Should be in the two to three minute range. Sometimes you need to do it 3 or 4 times to get an accurate reading. You can download a chart for the species and thickness of wood for better accuracy.

OR, you can get a cheap moisture meter, probably a better idea if you really need to know. :)

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pintodeluxe

4859 posts in 2280 days


#5 posted 12-09-2013 08:05 PM

^ Wow. Now I have truly heard it all.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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Mainiac Matt

5999 posts in 1795 days


#6 posted 12-09-2013 08:19 PM

Weigh boards when fresh cut… mark weight on each board… sticker and let air dry…

Come back at a future date and weigh the boards again. The difference is freed moisture.

Repeat over time. eventually, the weight will stop going down. Then your at equilibrium with the storage environment.

-- Pine is fine, but Oak's no joke!

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Dutchy

2022 posts in 1635 days


#7 posted 12-09-2013 08:24 PM

Hello Wiwildcat,

You can do it also with two multimeters
Look at the site of Matthias Wandel called Woodgears.

Maybe this will help you.

-- My englisch is bad but how is your dutch?

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Post_Oakie

84 posts in 1620 days


#8 posted 12-09-2013 08:29 PM

And I thought the tongue test was only good for checking the temperature of very cold metal gates!

The old rule of thumb is 1 year of air drying per inch thickness, but there is a lot of variation in climate and species. There are actually just a few simple things to take into consideration; wood moves more in width and thickness (as much as 8%) than in length (typically about 0.1%). Doors and cabinet frames were built so that the panels could “float” inside a frame as moisture content changed. Trestle tables had wedges that could be tapped in to tighten joints as necessary. For wide surfaces, alternating the face (wood tends to cup in a way that straightens out the growth rings) keeps the entire surface from cupping and cracking. We still use a lot of these designs (even with particleboard), but few people know why.

The concern about insects is valid, especially the powder post beetle, which loves hickory, pecan, and ash. You don’t want those little buggers in the house, and if you sell the furniture, you don’t want to be responsible for an infestation of your customer’s home.

-- Good judgement comes from experience. Experience comes from bad judgement.

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GOOD LUCK TO ALL

418 posts in 1195 days


#9 posted 12-09-2013 08:43 PM

And I thought the tongue test was only good for checking the temperature of very cold metal gates!

LOL,
If nothing else you will know what your wood tastes like…
hehehe

View wiwildcat's profile

wiwildcat

58 posts in 1429 days


#10 posted 12-10-2013 12:01 AM

Thanks for responding, fellow lumberjocks. All the information is good in helping me understand wood drying. I think I will try the miltimeter test. My beef with moisture testers is knowing the accuracy of the unit and I would assume that you get what you pay for.
I have some cherry and walnut drying in my garage for a couple years now. When I bought it, I was told it was about 10-12 % moisture content. My garage is only heated to 50 deg unoccupied and 65 deg occupied. I think it is dry enough but wanted to be sure.
Anybody want to recommend a moisture meter that has served them well and that has been tested, calabrated.

-- Wisconsin Wildcat

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wiwildcat

58 posts in 1429 days


#11 posted 12-10-2013 12:11 AM

..

-- Wisconsin Wildcat

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WDHLT15

1572 posts in 1943 days


#12 posted 12-10-2013 03:21 AM

Your wood in the garage is still probably about 10 – 12%. It will not get any drier than that unless you bring it into a climate controlled space (heated and cooled) or you put it in a kiln because of the humidity in the garage. Bring what you need for your project inside and stack it with stickers (spacers) in an out of the way place (like maybe behind the couch), and in a month, your wood will have equalized with the inside environment and be good to use.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT40HD35 Sawmill. Nyle L53 Dehumidification Kiln. hamsleyhardwood.com

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Post_Oakie

84 posts in 1620 days


#13 posted 12-10-2013 04:39 PM

I can just see my wife’s reaction to a stack of wood behind the couch! It would probably come close to when I replaced the oil pump in my Husqvarna on the kitchen table (in my defense, I DID put newspapers down first). Too blasted cold to do it in the shop. She puts up with a lot, especially since I got serious about making sawdust. I suppose it’s just as well that my portable sawmill isn’t portable enough to bring indoors!

Is the wood stickered in the garage? How is the air flow around it? What do you plan to make with it? WDHLT15 is right about the moisture content.

It would be interesting to put a hygrometer & thermometer in the garage and keep track of the relative humidity—that’s what impacts moisture content (not temperature, though warm air has more capacity to hold water vapor, so as air warms up, the RH goes down). If stickered, wood will reach an equilibrium moisture content based on the average RH & temp. Here’s a link to a calculator: “EMC calculator”: http://www.csgnetwork.com/emctablecalc.html

In general, pin-type moisture meters are cheaper and accurate. I use the oven dry method, myself, but you do not have to sacrifice a piece of wood every time. You can weigh as many pieces as you want to use for samples, then cut and oven dry a piece from the middle of one of the pieces. Then use the ratio of the weights. If the sample starts out at 1.12 kg and dries to 1.00, kg, it had 12% moisture content when you started. Its weight at 1.08 kg would have been 8% moisture content. Any sample will be at 8% when it reaches (1.08/1.12)= 96% of its original weight at 12%. You could also use this to calibrate your moisture meter for a given species.

-- Good judgement comes from experience. Experience comes from bad judgement.

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Thuzmund

142 posts in 1096 days


#14 posted 12-10-2013 05:19 PM

The great Roy Underhill, during his first season of the Woodwright’s Shop, advised viewers to place their bare lips against the wood to gauge it’s moisture content. If it feels extra cold, that’s because there’s still a lot of moisture in there. If it’s about room temperature, this means it is about the same level of moisture as the room.

Check out his series online or at your local library :) The early seasons are the best!

-- Here to learn

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wiwildcat

58 posts in 1429 days


#15 posted 12-11-2013 02:01 AM

Post_Oakie….. The wood is stickered with air flow. I think the MC would be about the same as when bought. Being in a garage that is used 1st for cars, 2nd wood, I like the hygrometer idea. I think i will now try the oven test on a couple samples, i have read up on it and would be accurate. Thanks for your input.
I am still not convinced about the cheap-o’ moisture meters and don’t want to sink the money right now into a meter with inputs for wood species, and wood temp, like a delmhorst model. I will just have to put that one on a future to buy list. After I do the oven test, information the wood will be moved indoors for a couple months and then repeat the test.

Thanks everyone, good information here.

-- Wisconsin Wildcat

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