Wood-Genie, you are using a moisture meter to check your wood. One thing you should know is that the entire wood industry expresses MC in wood using what is called "dry-basis". Dry-basis means that the weight of the wet wood is first determined, the water is removed (usually in an oven until it stops losing weight) and the final weight is recorded. The difference between the weight of the wood and the oven-dry wood is then divided by the weight of the oven-dry wood to get the starting dry-basis MC of the wood.
For example, taking a piece of wood that weighs 10 pounds and drying it in an oven until all the moisture is gone might give you a final weight of 7.5 pounds. The original water weight would then be known to be 2.5 pounds.
Dividing 2.5 by 7.5 (the oven-dry weight) gives a starting MC of 33%.... dry-basis. When we think of this problem, we say, "Well, the wood weighed 10 pounds, it lost 2.5 pounds, so it must have been 25% MC to begin with." And you would be correct... if you are speaking of the wet-basis method of expressing moisture content.
The problem with using a moisture meter is that they are all calibrated for the dry-basis method of expressing MC, because that is the method the wood industry uses to express MC. The fact is, the higher your starting MC is, the more difference there will be between these two figures. It's simply mathematical.
If you are getting a reading of 27% on your meter, the actual MC of your wood using the wet-basis is only 27/127 = .21 x 100 = 21%MC. Saying it differently, if the meter says it has a MC of 27%, there is only about 21% water in it by weight. Doesn't make sense, but this is the truth.
On the other extreme of your measurements, if your meter says the wood is at 18%, the wet-basis MC of your wood is 18/118 = .15 x 100 = 15% water by weight.
The bottom line is that your meter is really telling your that your wood only varies by 6% in water weight across the entire range of your measurements. Will wood that is 15% water by weight burn significantly better than wood that is 21% water by weight? I don't believe so, but try it in your stove and judge for yourself. To top it off, if you are using the meter correctly, you are splitting the wood and measuring the inside. What about the outside? The stove only knows about the average water content. If you are getting 27% MC on the inside but only 12% on the outside, your wood will be averaging less than 20% water weight for the entire split.
Lastly, moisture meters are really only measuring the resistance to the flow of electricity in the wood and expressing the resistance in %MC instead of ohms. But despite what your meter reads, they are only truly accurate up to about the fiber saturation point of the wood, which in nearly all wood is about 30% MC dry-basis. Above 40% they are nearly useless. So when you get a reading of 27% on your meter, you are already near the end of the range of accuracy that the instrument can deliver. Species variation at this MC can account for a 2-3% difference in accuracy. Pro meters have programs built into them to account for species variation at higher moisture contents. Cheap meters don't.
I think that, in general, the moisture meter is an interesting tool, but I wouldn't let an almost arbitrary reading it gives me determine if the wood is ready to burn. I'd put it away for the season if you don't want to give yourself an ulcer. My gut tells me your wood will burn at near peak efficiency.
Thanks!
