Moisture Content of Firewood? Good Information

[Burnin Since 1991]

My goal is to take firewood from my outdoor stack and split it and check the moisture content to see if it's good to burn.


I split 4 pieces of oak at 2:05pm. The original splits were between 4 and 6 inches and 16 inches long.

The temp outside was 53 degrees and humidity 51% and cloudy all day. Low temp this morning was 35 and 65% humidity. Since I was making kindling, I made little ones out of big ones. Brought them inside and the air temp was 68 and humidity was 43% inside the house. .

I tested the kindling and the IR showed 60.2 degrees for all the splits and MC shows a range of 11.6 and 16.8.

Funny that the IR is showing 60.2 degrees as it's no where near that warm nor has it been any where near that warm in the last 4-5 days. The wood is palleted and stacked two rows deep, 6 feet high and about 18 feet long. It has been only top covered with a brown tarp for the last 3-4 days. All of the original splits were taken from the top, just under the tarp. I didn't choose them that way, it's just what was easiest for me. I can IR the wood pile again to see what the numbers of other random pieces in the stack are temperature wise. Also planning to to do this same exercise but with the original splits only split once.

The next step is to let the kindling come up to temp in the house and see what the moisture content does.

On the thermometer, the top two are outside temps, The third one down is a utility room and the bottom one is inside the room.

Stay tuned, More to come!

 

[Dieselhead]

If your sig didn’t give it away I would of guessed you were retired 🤣

 

[Burnin Since 1991]

If your sig didn’t give it away I would of guessed you were retired 🤣

good call

 

[bigealta]

So test on fresh splits, that means split it and stick the pins in right away. No waiting around.
It's unclear if you did the test right away or after they sat around?

 

[stoveliker]

I suspect the wood was frozen if you didn't bring it up to temp before splitting (and then right away measuring).
IR thermometers assume certain materials (emissivity), and rough wood surfaces are not likely correct for that.

If the wood was indeed frozen, your wood is likely too wet...

 

[Burnin Since 1991]

I split the wood outside, brought it in the house and waited some for the wood to warm up. I have some warm wood right now and I will split them later today and see what they measure. That initial test was two months ago. I've watched the wood burn with very minimal water boil now and again. Stove and flu temps are normal and no buildup in the cap, though I will be doing a chimney brush during the next reasonable warm up.

My goal, and I failed to follow up with; was how much difference in MC would there be with a just up to temp piece of fire wood from outside fresh split and a piece of wood that had been indoor for 3 days (in the rack, 18 inches away from the woodstove). Same species same size wood. The next step would be to keep those fresh splits and check the MC and 2 days and then a week.

I will start my experiment over today and post the results.

Would I need to fresh split them each time?

 

[brenndatomu]

Yeah, an ir gun needs a smooth flat black surface to be totally accurate

 

[stoveliker]

I split the wood outside, brought it in the house and waited some for the wood to warm up. I have some warm wood right now and I will split them later today and see what they measure. That initial test was two months ago. I've watched the wood burn with very minimal water boil now and again. Stove and flu temps are normal and no buildup in the cap, though I will be doing a chimney brush during the next reasonable warm up.

My goal, and I failed to follow up with; was how much difference in MC would there be with a just up to temp piece of fire wood from outside fresh split and a piece of wood that had been indoor for 3 days (in the rack, 18 inches away from the woodstove). Same species same size wood. The next step would be to keep those fresh splits and check the MC and 2 days and then a week.

I will start my experiment over today and post the results.

Would I need to fresh split them each time?

Yes, if you split, let it warm up and then measure, the surface has already dried out more, leading to a lower reading than reality.

 

[Burnin Since 1991]

So finally found my round tuit. It was right here the whole time.

I split an 8" x 16" x 2.5" piece of red oak into 4 splits at 1pm Eastern.

Just for fun, I tested the MC of the exposed split and it measured 11% on all sides.

It was overcast, 21 degrees F outside and the wind chill/ feels like was 15.

The wood was split cold into 4 pieces all approximately 1-2.5" (square-ish) x 16". Again, just for fun, I tested all the surfaces. The first split measured 13% and the 2nd split was also 13% on one side and 16% on the other. The results on the other two splits were the same. (so 11% on the outside, 2 inches in it was 13% and more or less the center was 16%)

I brought all inside and after 2 hours inside, the splits were all at room temps.

Split 1 was 11% on the outside and 12% on the inside. Split #2 was 18% on both sides. Split 3 was 18% and 13% and split 4 was 12% on the inside and 12% on the outside

I tagged each piece with a numbered push pin and I will check them again tomorrow.

 

[bigealta]

So i wanted to know the same thing. How much different the moisture content would be from a split that was warm for maybe just a day, to one that was close to the woodstove for about 3 days.

Surprisingly i found that moisture content had almost no change on fresh splits from both groups.
(Both groups measured the same = no change)

That does not mean that drying splits out by the woodstove does not help, it does help for sure. (It helps dry the Exterior only)
It just doesn't "Season" your splits very much at all.
If i recall these were most likely red oak splits, and i think they measured around 20-21% range tested immediately on fresh splits.

And the splits tested were pretty large, starting at maybe 3"-5" thick ranges and 18" long.

 

[stoveliker]

That does not mean that drying splits out by the woodstove does not help, it does help for sure. (It helps dry the Exterior only)
It just doesn't "Season" your splits very much at all.

That still helps as it makes the splits take off faster, rather than lay there smoking, and starting to burn dries out the rest of the split faster, leading to a decent fuel content of the firebox sooner.

Yet, best to have them properly dry

 

[Burnin Since 1991]

Checked the red oak splits again today at 0845 Eastern. The splits have been in the house for 36 hours.
Split 1 10/12% Split 2 14/14% Split 3 14/8% and Split 4 was 7/6. It's 69 degrees in here, probably the wood is at about 80 degrees. Humidity even with a wick evap humidifier running in the room is only about 30%.

I have another red oak split here that is 8" x 3" x 16" that has been in the house for a week. As soon as I can get outside, I am going to split it and see what it looks like.
The sapwood is pretty punky so I won't bother with testing it though I will skin some of it off and see what it measures.

 

[bigealta]

Split it in 1/2 so u have 2 4"x3"x16" splits.
Test parallel to the grain in the middle and a few other spots.
(you are trying to find the wettest part of the wood.)

 

[Burnin Since 1991]

Split it in 1/2 so u have 2 4"x3"x16" splits.
Test parallel to the grain in the middle and a few other spots.
(you are trying to find the wettest part of the wood.)

I have been checking them in two or three spots. I am seeing minor deviations near the edges and ends but nothing too drastic. What I'm trying to find out is how much of a difference is there between a cold split, a warm split and then 36-48 hours and comparing that to a full size split that has been next to my stove in a rack for a week.

It seems many folks don't think it makes a difference to how their wood burns and I'm trying to see what the numbers indicate.

 

[bigealta]

I have been checking them in two or three spots. I am seeing minor deviations near the edges and ends but nothing too drastic. What I'm trying to find out is how much of a difference is there between a cold split, a warm split and then 36-48 hours and comparing that to a full size split that has been next to my stove in a rack for a week.

It seems many folks don't think it makes a difference to how their wood burns and I'm trying to see what the numbers indicate.

yes i am too.
i researched the difference and it seems like you generally need to add around 2 or 3 percent for measuring near 32F to 70F.
so 18% at 32F would most likely be around a 20 or 21% true read.
(The meters are generally set to read at 70F.)

 

[Burnin Since 1991]

yes i am too.
i researched the difference and it seems like you generally need to add around 2 or 3 percent for measuring near 32F to 70F.
so 18% at 32F would most likely be around a 20 or 21% true read.
(The meters are generally set to read at 70F.)

I have delayed the latest split testing. It's now snowing on top of the freezing rain from the last 12 hours. Maybe tomorrow

 

[bigealta]

I just tested 2 pieces of locust yesterday
Temp 50f-55f
14" split Outside surfaces tested 12%,,,, Inside fresh split tested 20%
18" split Outside surfaces tested 16%,,,, Inside fresh split tested 26%

And i did bend 1 of the pins on the meter a bit as i sunk them in as deep as i could. (Locust is Hard)
You can really see the readings go up as you get the pins in deeper and deeper.
From now on i'll probably not press as hard and just ADD about 2% to my readings.

 

[Burnin Since 1991]

My last meter had non-replaceable pins. Bought one with the replaceable ones. Already starting to bend one of them.

 

[brenndatomu]

I had some hickory, or something real hard, don't recall for sure anymore, but the pins wouldn't go in very far, so I marked the wood with the pins, then stabbed holes with a sharp awl, and hammer, then immediately tested in those holes...used my palm to really seat the pins in the holes...worked well.

 

[all night moe]

I had some hickory, or something real hard, don't recall for sure anymore, but the pins wouldn't go in very far, so I marked the wood with the pins, then stabbed holes with a sharp awl, and hammer, then immediately tested in those holes...used my palm to really seat the pins in the holes...worked well.

That's a great idea.

 

[Dieselhead]

If you bring a split up to room temp, split it and immediately check the mc I don’t see the need to insert pins fully. You are basically reading the area the fully inserted pins would be.

 

[brenndatomu]

If you bring a split up to room temp, split it and immediately check the mc I don’t see the need to insert pins fully. You are basically reading the area the fully inserted pins would be.

That's true...but for some reason the reading seems to change a bit with depth...contact surface area maybe?

 

[stoveliker]

If you bring a split up to room temp, split it and immediately check the mc I don’t see the need to insert pins fully. You are basically reading the area the fully inserted pins would be.

It's not the depth of the MC that is the issue, it's The contact resistance that's the issue. It's a two-point measurement and the contact resistance is in series with the load you want to measure.
Having tips not in deep increases the contact resistance leading to lower mc readings.

 

[bigealta]

Here is why you Do need to sink deeply, or add a few percent to a non deep reading.

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[bigealta]

My last meter had non-replaceable pins. Bought one with the replaceable ones. Already starting to bend one of them.

You can bend the tips of the bent pins back to straight with plyers if you are careful.