Moisture measurement

[woodchuck357]

I just finished running a new batch of tests on the moisture levels in some wood samples. Wanted to come up with some sort of simple guide for using a inexpensive meter to get an accurate reading.
The testing process is not completely accurate and is time consuming but it is as good as I can do with the limited lab I have.
The process starts by splitting the center out of a sample and cutting the ends off to remove surface wood. The samples are weighed with a very accurate balance scale. Then they are oven dried with weighings about every half hour. When two consecutive weighings have shown no change in weight the dried weight is subtracted from the original weight to give the weight of the water removed.
The water weight is devided by the dry weight then multiplied by 100 to come up with the percentage of moisture in the sample before it was dried.

 

[Marine5068]

lol

 

[Whitespider]

Wow‼ You need to simplify the calculation. And don't split it or cut the ends off... you're lookin' for the "relative" moisture content.
mc = (ww-wd)/ww
So if you start with a 18 lb 7 oz chunk of wood that dries down to 11 lb 13 oz just convert to ounces and run the calculation...
(295-189)/189=.56084 (or... 56.1%)

were you thinkin'??

Oooops... had to repair the calculation (damn beer).
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[chucker]

??W. T. H..........!?????????????????????????? LOL

 

[chucker]

that's like asking how many microns are in a cubic foot of firewood, would that be able to burn through a 6" flue?????????????? lol

 

[zogger]

So how close is your meter then?

 

[woodchuck357]

Having problems with meter consistency. Just gathering data. Since it only reads a high of 30 percent even when the actual percentage may be over 100. Generally, it reads low on higher and high on lower.
I don't see how the figuring could be simpler.
The amount of moisture is close to the same throughout a piece once the outside half inch is removed from the sides and 2 inches from the ends.
To keep drying times shorter samples are about one by one and a half inches by ten inches long.

 

[fixit1960]

Having problems with meter consistency. Just gathering data. Since it only reads a high of 30 percent even when the actual percentage may be over 100. Generally, it reads low on higher and high on lower.
I don't see how the figuring could be simpler.
The amount of moisture is close to the same throughout a piece once the outside half inch is removed from the sides and 2 inches from the ends.
To keep drying times shorter samples are about one by one and a half inches by ten inches long.

Wow, you must not have a job or a lot of time on your hands. I cut it and if standing and green it goes on next years pile. I use an OWB that will take a 52 inch long piece of wood. If it needs split I cut to 24 inch long so it will fit on the splitter and I only split it up small enough so I can pick it up and chuck it in the door. If the bark is off and it's laid for a year or more it goes on the pile to go into the OWB this season. That's a lot of thought and time and a lot of splitting for wood to burn. I like to keep it simple.....I figure the less handling and processing the more time to be in the shop turning out work. I have to figure my time worth something, but to each his own...

 

[Jerryv88]

Having problems with meter consistency. Just gathering data. Since it only reads a high of 30 percent even when the actual percentage may be over 100. Generally, it reads low on higher and high on lower.
I don't see how the figuring could be simpler.
The amount of moisture is close to the same throughout a piece once the outside half inch is removed from the sides and 2 inches from the ends.
To keep drying times shorter samples are about one by one and a half inches by ten inches long.

How can the percentage be over 100???? Is that like "giving it 110% effort"?

Jerry

 

[woodchuck357]

How can the percentage be over 100???? Is that like "giving it 110% effort"?

Jerry

Some wood can hold more water than the wood weighs dry. I have looked at some charts that show green red oak as having 80 percent water, but my tests show fresh cut red oak to be around 96 percent. Sycamore is one of the hardwoods that are well over 100 percent. Pines are often near 200 percent.

 

[woodchuck357]

Wow, you must not have a job or a lot of time on your hands. I cut it and if standing and green it goes on next years pile. I use an OWB that will take a 52 inch long piece of wood. If it needs split I cut to 24 inch long so it will fit on the splitter and I only split it up small enough so I can pick it up and chuck it in the door. If the bark is off and it's laid for a year or more it goes on the pile to go into the OWB this season. That's a lot of thought and time and a lot of splitting for wood to burn. I like to keep it simple.....I figure the less handling and processing the more time to be in the shop turning out work. I have to figure my time worth something, but to each his own...

Mostly retired, take down a couple of trees a week, haven't found any thing worth watching on TV in years, and I like knowing things, not guessing.

 

[4x4American]

Makes sense to me. That's proberly how I would go about it if I were to go about it.

 

[4x4American]

Did you know, that the proper spelling of "devided" is divided? Look that up in your Funk and Wagnall!

 

[woodchuck357]

Did you know, that the proper spelling of "devided" is divided? Look that up in your Funk and Wagnall!

Sorry if my misspelling hindered your comprehension, I'll try to do better in future posts.

 

[Whitespider]

How can the percentage be over 100???? Is that like "giving it 110% effort"?

The moisture content of wood is not expressed as an absolute value, rather a relative value by weight (or more correctly, mass)... weight of moisture relative to the weight of dry wood.
For example; green, fresh-cut Cottonwood has about 150% moisture content. Meaning a 100 lb green, fresh-cut Cottonwood log is 40 lbs of dry wood and 60 lbs of moisture 40×1.50=60.
The only way to know the true moisture content is to first weigh a piece of wood and record the value (say it's 38 lbs), oven dry the piece until it stops losing weight and record that value (say it's 16 lbs), then run this calculation...

MC = (wet mass-dry mass)/dry mass(100%)
MC = (38-16)/16(100%)
MC = 22/16(100%)
MC = 1.375(100%)
MC = 137½%

Hope that helps
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[Hddnis]

Do you have a calculation to compensate for the type of bar oil you used?

That could throw your measurements waaaaaay off.



Mr. HE

 

[woodchuck357]

Do you have a calculation to compensate for the type of bar oil you used?
That could throw your measurements waaaaaay off.
Mr. HE

Only if I had used the distillation method to remove and collect the moisture.

 

[Hddnis]

Ah, I see, you trying to stay legal by not using a still and all that.


Mr. HE

 

[Whitespider]

You don't have a still??
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[woodchuck357]

Not one for wood.