# What's The Mc?



## Mike Jones (Jan 20, 2014)

For most of us here on WoodBarter forums, the moisture content of wood offered up for sale or for trade is an important consideration. Sometime it is VERY important or even critical, yet this important information is seldom provided. Perhaps worse, it is guessed at, or expressed as “how long it has been in the barn” or “what year the tree was cut down”....expressions that are usually meaningless ways of describing this important element.

A moisture meter might be an expenditure that seems excessive for the level of trading that we intend, or the relative value of the wood might not warrant buying one. However, the moisture content of wood can be determined easily, quickly, and inexpensively.

The Moisture Content (MC) is expressed as a percentage of the water weight to dry weight of a piece of wood and we can find that easily with an inexpensive postal scale and some sort of drying oven. The oven can be the oven/range in your kitchen, a microwave oven, crock pot, or even a shop made oven using incandescent bulbs for the heating element. Whatever your choice, there will be advantages and disadvantages to consider, and there are too many variables to go into depth here, but the essence of the devices are all the same: heat the wood sample until no more water will come out. 220 degrees is the target heat for conventional ovens.

Your wood sample can be any shape or size (even shavings could work) because all we need to know is the difference between the weight before the oven and the weight again after the oven.(If you need to know the MC per given measured cubic foot or board foot, there would be a simple mathematical calculation to follow, and you would need to be able to measure and cut your sample piece first to do this.)

Here is what you do. Weigh your sample piece, write down the weight, put the sample in the oven, weigh and write down the weight at intervals, like every hour or so (handle with tongs or oven gloves!) and when the weight does not change give it one more interval to be sure. Subtract the dry weight from the wet weight and divide by the dry weight then multiply by 100. That is the Moisture Content


Wet Weight - Dry Weight x 100 = %MC
Dry Weight

For the microwave, the intervals will be shorter, and you must watch carefully that your wood temperature does not get over 350 degrees lest you start a fire in there. Shorts bursts of a minute or so at a time, and opening the door to let moisture out, should keep you out of trouble. With this method, the 220 degree target would be difficult to measure (and not important) but continual weighing until the weight remains constant will yield the same result.

How long it will take will vary dramatically depending on the MC to start, the species, the size of the sample, and the method/device you use. For the same reasons, how much electricity would be used and the costs will also vary. The microwave method would be the least costly, convection oven next and range/oven the most. Very roughly computed, you should be able to run a test for a buck or two and a batch of samples will cost little more than a single piece. Most postal scales only weigh to a tenth ounce, so we cannot expect laboratory level accuracy, but typically, we don’t need know the MC to anything like three decimal places, and this method will get you close enough for our purposes.

Please use your head, set timers, pay attention, be safe, and........start posting moisture content!

Reactions: Like 4 | Informative 2


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## Molokai (Jan 21, 2014)

Thanks Mike! I learned something new today.


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## rbhandcrafted (Jan 21, 2014)

thank you for the reminder to use the MM


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## jmurray (Jan 21, 2014)

Out of curiosity I'm gonna ask you this.

If I buy kiln dried wood , how much can the mc fluctuate due to season? Is it enough to make a difference?

Kinda on topic?


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## ButchC (Jan 21, 2014)

Has anyone else tried a non probe MC meter like this one? 



 
(sorry. Cant figure out how to rotate phone pics). Mine seems to work pretty well and the cost was only about $35-$40.

Butch


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## barry richardson (Jan 21, 2014)

Hey, shouldn't this go in the daily rant section? Just kidding, I'm totally on board with you...

Reactions: Like 1


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## Mike1950 (Jan 21, 2014)

jmurray said:


> Out of curiosity I'm gonna ask you this.
> 
> If I buy kiln dried wood , how much can the mc fluctuate due to season? Is it enough to make a difference?
> 
> Kinda on topic?




The guitar blanks I buy have been KD'd to 6%- then if they are rejected by buyers- they end up stored on pallet and depending where on coast they are can end back up at 13%.

My shop- wood heat this time of year wood is dry-very dry 6-7%- summer-it is cool in there compared to outside and moisture is higher. they can get up to 10%
the boxes I have in there any other things I have made seem to stay quite stable with the yearly cycle. Sure do not want to bring green wood in there now-cracks fast.


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## Mike Jones (Jan 21, 2014)

jmurray said:


> Out of curiosity I'm gonna ask you this.
> 
> If I buy kiln dried wood , how much can the mc fluctuate due to season? Is it enough to make a difference?
> 
> Kinda on topic?



Kiln-dried will typically measure 6% to 8% MC and it will begin to gain moisture from the minute it comes out of the kiln. How much fluctuation will depend on many factors...species and where it's stored may be the biggest...but once the wood hits Equilibrium Moisture Content, it wont fluctuate much just from season to season unless you live in a climate that has extremes in relative humidity.

Butch...I use a Wagner non-prong meter like yours (cost a bit more though)


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## Treecycle Hardwoods (Jan 21, 2014)

jmurray said:


> Out of curiosity I'm gonna ask you this.
> 
> If I buy kiln dried wood , how much can the mc fluctuate due to season? Is it enough to make a difference?
> 
> Kinda on topic?


To answer your question yes it can make a difference. I tell my customers that even though the tree is dead the wood is very much alive. Depending on your climate your MC may go as high as 13%+ this variation is known as EMC. My EMC range in Wisconsin is 8-13% for me to keep my wood in the 6-8% range I need a climate controlled environment. 

There are a couple common situations where MC isn't critical.
1) general turning. In fact I sell to many wood spinners who prefer fresh sawn wood to dry wood. 
2) bending. Ww who bend wood almost always shun kiln dried wood. 

A couple of situations where MC is critical
1) luthiers need to know what the MC is because building quality instruments require good stable wood almost always qsawn for stability during seasonal changes.
2) fine furniture builders need to know what the MC is to assure joints won't loosen and table tops remain flat. 


Another important note on MC is that often you will get different readings from the same board. While MC is an important piece of info to know when selling/buying wood I think an air dried/kiln dried or recently sawn is more important. MC as part of a wood description becomes critical only when a specific project dictates a MC within a certain tolerance. Ie instruments and fine furniture. 

If a seller has a request for the MC of a board the post opening this thread is great to help you determine the MC without a meter. I think @ButchC mentioned (with pix) an affordable model that will deliver reasonable results for the non professional. If you want to go a step further you can get a hand held pin meter for about 100-120. The best meters are 200-400+ and require driving longer pins into the interior of the board. I have never used one of the high end models regularly because they are a PITA to get out once you drive them into the wood. 

As a professional and hobbiest I have gotten satisfactory results with hand held meters. 

To sum it up....
If you are a seller of wood know who you are selling to and why they need the wood. If they need to know MC make sure that you include it in your description or at a minimum be able to get I quickly upon request. 

If you are a buyer you need to know if it is critical to your project. If MC is important for your use don't feel bad for asking the seller what it is. A reputable seller will not shy away from that question.

Reactions: Like 1 | Informative 1


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## HomeBody (Jan 22, 2014)

Don't buy the moisture meter at Lowe's with the remote probe on a wire. The wire is super fragile and mine only lasted a week. Whaaaaaa! Gary

Reactions: Like 1


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## Mike Jones (Jan 22, 2014)

There are a couple common situations where MC isn't critical.
1) general turning. In fact I sell to many wood spinners who prefer fresh sawn wood to dry wood.
2) bending. Ww who bend wood almost always shun kiln dried wood.

*I'm not sure what you mean by "general turning", but I, and others here make: lidded boxes, lidded urns, hollow forms with lids and finials, travel mugs, bangles, turkey pot calls (and strikers) tea pots, models, and pens...and we really need to create these at or near EMC because these forms will fail if the wood moves too much from losing or gaining moisture. I can't speak for others here, but my creations demand every bit as much critical attention as those of the luthiers and furniture makers.

There are many instances where I prefer green for a turning over dry. Some of those instances are because the wood doesn't cut as cleanly when dry as green and others because of difficult dust management.*

As a professional and hobbiest I have gotten satisfactory results with hand held meters.

To sum it up....
If you are a seller of wood know who you are selling to and why they need the wood. If they need to know MC make sure that you include it in your description or at a minimum be able to get I quickly upon request.

If you are a buyer you need to know if it is critical to your project. If MC is important for your use don't feel bad for asking the seller what it is. A reputable seller will not shy away from that question.[/quote]

Reactions: Like 1


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## Mike1950 (Jan 22, 2014)

"2) bending. Ww who bend wood almost always shun kiln dried wood." I will add to this Greg- I think steam benders prefer air dry to KD. As a bent lamination guy I really cannot tell the difference.
As a Flat worker only I really shy away from wet (Green) wood But occasionally get some. I make sure to ask when I am a buyer- solves misunderstandings down the road.


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## Treecycle Hardwoods (Jan 22, 2014)

@Mike Jones General turnings IMO is something that doesn't have fitted parts. So no lids, no pens or other kit items, no table legs, etc... I rarely have hollow form or bowl blanks dry at the mill because the vast majority of my customers buy their turning stock green and rough turn it then come back and turn the rest later. I even have guys do this when they intend to fit a lid down the road.

I agree with you that MC is important to consider. I also believe that a description that doesn't include a MC but does have referecne to where the wood has been is acceptable Ie kiln dried, air dried in barn 10 years, sawn green and sealed, fresh sawn last month, etc... Using those descriptions will tell you if the boarda are at EMC or if there is no snowballs chance it is dry. If and exact range is needed the seller should be able to easily and quickly be able to share that info with a customer. For example: A customer in the southwest may be ordering lumber from the midwest (2 very different EMC's) A good seller will bring up the EMC difference and a knowledgeable buyer will ask. WI to AZ is a 8-10% difference in EMC and could very easily cause problems once the wood is shipped. To back up my argument i surffed the web for a bit looking at some well known online sellers and the vast majority of what I saw was a simple kiln dried or not kiln dried.

The point I was trying to make in my first post and now is selling wood within your region the MC is almost a moot point if is has been kiln dried and air dried for a substancial period of time. BUYER/SELLER BEWARE of shipping lumber from one region to another MC IS A BIG DEAL ESPECIALLY IF YOU ARE SHIPPING INTO THE SOUTHWEST!!!


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## cabomhn (Jan 22, 2014)

If anyone is interested I can post how to make a standard multimeter turn into a moisture percentage reader. It's not super straight forward but most people have multimeters and I definitely don't want to shell out $50 for a moisture meter.


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## Fret440 (Jan 22, 2014)

Matt, I'd be interested in that! Being as I don't want to be microwaving or cooking in our kitchen (wife wouldn't be keen on the smell), and I already own a multimeter to use when I'm doing wiring.

Jacob


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