Results of drying experiment

In late Spring I did an experiment drying wood. Nothing really surprising, but it does put things in perspective. I had two fresh chunk of red oak right off the splitter. I tested the moisture and weighed the two pieces. I then just stuck them in the garage and weighed them yesterday, re-split and tested the moisture again.

I have always been of the opinion that wood dries faster in open air exposed to the sun. This wood was under my workbench out of the sun.

The Results:
April 13,

Piece #1: weighed 8.5 #'s Moisture was at 25%
Piece #2: weighed 7 5/8ths #'s, moisture was at 25%

November 15,

Piece #1 weighed 6#'s, moisture was at 19%
Piece #2 weighed 5#'s, moisture was at 16.5-17%

 

Standing dead? Pretty dry to begin with, but also some decent moisture loss in 7 months for red oak. Thanks for sharing

 

No these were culls off a logging operation. Wood was very large and cut last December. I hauled home and split in April.

 

How much room you got under your bench? Seems like a good spot for drying

 

Well I don't know about a drying spot, the spiders seem to really like it.

 

Your weight observations and MM readings do not come close to correlating with each other. Either one of them is grossly inaccurate or the spots that you checked the moisture readings weren't indicative of the true moisture content of the wood. My guess is the wood moisture was way beyond the range of your meter last April and measured inaccurately. There is no way that you lost over 25% of your actual weight but only dropped 5 to 8 pct points of moisture.

Remember that % moisture is expressed as the weight of water compared to the weight of wood if it is bone dry with no moisture at all. Think of it as you always have 100 parts of wood and the % moisture is the parts of water. So at 20% you have 100 parts wood and 20 parts water. At 19% you will have the same 100 parts wood but only 19 parts water. So you can take the weight of your wood, divide it by 100+ the pct water to figure out what one part weight and then divide its weight at any other observation by what one part weighs to figure out its pct. It will be 100 minus that number. You can also determine a piece of woods weight at any moisture content by multiplying what one part weighs by (100+the target moisture content)

So with your first piece starting at 8.5 pounds and 25%. 8.5/125= .068. One part of your wood/water piece weighs .068 of a pound. If I drop the moisture to 19 percent you will have 119 total parts, so your piece will need to weigh 119*.068=8.09 pounds

Let's do this with your current readings and figure of what it had to start at. At 19% and 6 pounds now and starting at 8.5 the beginning moisture would have needed to read about 68.6%. The math works like this. 6/119=.0504 so one part weighs in at .0504 pounds. Take the starting weight and multiply it by that. 8.5/.0504=168.58. Subtract off 100 for the hundred parts of wood and you have 68.58 parts of water or 68.6%.

Figure it out if you had the pice bone dry coming from 6 pounds and 19%. 6/119=.0504. .0504*100=5.04 pounds. The 100 in that equation is the parts of wood that you have, which is always 100.

If your weights are correct and your current reading is accurate means your wood started at 68%. We know that 68% is way above the range that a moisture meter will work and that plausibly explains your readings. If my assumptions in that are correct you should note that you achieved a lot more drying than you credited yourself with.

bogydave, that's the math that you asked me to explain. Ask if you need more clarification. If you are conceptually able to think of it in parts of the total instead of percent I think it becomes pretty easy to understand. Just remember if you divide the weight of your split by what one part weighs it can never be less than 100 because you always have 100 parts of wood. If the moisture % is 100 or over your number will be 200 or more. Because if it's 100% that means you have equal parts of water and dry wood, each at 100.

 

Well Mr. Bunion we have a severe difference of fact and how to calculate percentages.

First off, I am quite adept at reading a kitchen scale when an object is placed on it. I am confident that I can read a kitchen scale better than 51.87694% of other individuals tasked with reading said kitchen scale. As far as reading the number off the moisture meter, since it is digital I feel all who read a number will get the same results.

Now for percentages. Here is a calculator for the less math oriented.

http://percentcalculator.com/?gclid=CNnozI-KgsICFc1_MgodQ3oAxw

In example #1.

8.5 # to 6# is a 29.411 % decrease which is a loss of 2.5 #s of total weight

8.5 times 29.411 % equals 2.5 #'s.

Well I'll be, that is exactly correct. Feel free to check the math. Let's move on two example #2:

Example #2.

We start with 7.625 (7 & 5/8ths) and it drops to 5 #'s even. That is a drop of -34.426 % which is 1.625 #s

7.625 times 34.426 equals 1.72 #s, So we have an error of 1.72- 1.625 of .1 #s or 1.6 oz.

Let's move on to the percentages:

Example #1:

25% to 19% is a -24% decrease

Comparing weight to moisture meters leaves an error 18.40% ( 29.411 to 24%)

Example #2:

25% to 17% is a 34% decrease

Comparing observed weight to moisture meter leaves an error of .426% (34.426 to 34%)

So you are critiquing my method for an error of .426%?????????

Please feel free to point out the errors in my math.



I made this post because I thought it was interesting and simply just that.

 

I never said your post was uninteresting, in fact I find it quite informative. And your math above is correct but your conclusion is wrong. You are confusing absolute weight loss with your percent moisture content. They do not correlate 1:1.

Remember that moisture content is express as the weight of water within a piece of wood compared to the weight of the wood if it was bone dry, no water at all.

At 25% that would mean that for every pound oven dry, moisture less wood there is 1/4 pound of water.

So with your 8.5 pound piece of wood measured at 25%, it will break down to 1.7 pounds of water and 6.8 pound of dry wood. 1.7/6.8=.25 or 25% moisture and 1.7+6.8=8.5 or 8.5 pounds in total combined dry wood and water. So your 8.5 pound piece of wood, using the April readings, contained 6.8 pounds of wood and 1.7 pounds of water. You checked it again in November. It weighed in at 6 pounds. That is impossible if your original readings were correct, it is less than the weight of the wood as originally observed. You would need to have lost all of the water and a chunk of the wood. Something is wrong. I showed above that your piece as measured in November would have been at 68% or thereabouts in April. That is way beyond the working range of a moisture meter. Like I said above, my gut feeling is you got faulty moisture readings in April and your wood was a lot wetter than your meter was capable of measuring. (And you achieved a lot more drying than you observed via the moisture meter.)

 

This is all way over my head. CSS 18 months and burn baby burn.

 

+1
I got a test going. Not sure what it tells me as far as what it's MC is..
The wood when CSS was wet & heavy. It's lighter weight now.
Still have now idea what the MC is now, but still wet IMO.
I have no idea how much the wood would weigh with 0% MC.
I know after 3 years, (1 in a seasoning row & 2 in the shed) it burns great.

So what's it's MC when I burn it ? dry !

But it is fun to see the rate the inside wood dries compared to the outside wood.

If I had a moisture meter, (but I don't) & I split it to measure the moisture,
then the test is done. I've split the wood I was testing.

One split has lost over 4 pounds so far, amazing to me how much water is in green wood.
Was 14.8 lbs, now 10.4 lbs. Lost 4.4 lbs of water in a month inside by the stove.
What's the math on that ? (30% loss in weight ? )
What's the moisture content with no assumptions. ?
That's like 1/2 a gallon of water.
& some people here put it in the stove, they say to burn, I say to boil LOL

 

Paul,

I don't know if this explanation makes sense or not. We are talking about two different things. The center of the split where the moisture reading was taken is heart wood. Heart wood has much less moisture in it than the sap wood. The Moisture meter will confirm this.

The total amount of weight lost is from the exterior of the split. This would make sense since sap wood has much more water in it, (i.e. sap) than does the interior heart wood. All things move from high concentrations to low concentrations thus the majority of the weight lost was near the bark and this is not where the reading was taken.

 

I think where FWbandit is coming from is that the wood is not a consistent density.
Personally don't own a moisture meter - and probably never will, if you want to get a real set of numbers on any wood it requires oven drying and weighing...

 

What's the fun it that. LOL

 

Remember battenkiller's tests, some people thought he was full of crap even though he had detailed data to go with the tests.

 

he was an animal - very detailed, oven dried blocks etc. I remember that thread very well - convinced me to start stacking and get ahead

 

Yea
Loved reading them.
The science behind it all is amazing.