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How can I tell if my wood is dry?
Q: My Dad used to determine how dry our fuel wood was by banging two splits together. He's no longer with us, and I never asked him exactly
what he was listening for. My wife and I recently purchased a wood stove and several cords of "seasoned" firewood, and the poor heating
performance of this high-rated stove has me suspecting that the wood is not as seasoned as advertised. Are you familiar with my Dad's technique,
or any other methods to determine the water content in wood?
There are several techniques you might use to determine the dryness of your fuelwood, some more reliable than others. Here are a few,
organized from most to least reliable:
1: Use A Firewood Moisture Meter:
The premise: these battery-powered devices measure the conductivity between two electrical probes inserted in the piece of wood. Since wood
doesn't conduct electricity, the amount of current flow between the probes determines the amount of moisture present.
The technique: to get a true reading from the heartwood, a sample log is split in two, and the probes are inserted near the center of one of the
fresh splits, aligned parallel with the wood grain.
What you're looking for: A reading of 25% or less indicates the wood is seasoned enough to burn; ideal moisture level is 20% or less.
2: Season It Yourself:
The Premise: with few exceptions, most wood species achieve ideal fuelwood moisture content after having been cut and split into stove-size pieces
and stacked out of the rain in a space where air can circulate to carry away the evaporating moisture for at least one year. Reportedly, some
tight-grain species (Oak is often mentioned) can take up to two years to properly season.
The technique: split and stack your fuelwood 1-2 years in advance. Make sure even wind-driven rain and snow can't get to your woodpile, and that
nothing is interfering with airflow through the stacks.
What you're looking for: never again having to trust a woodseller's claims about how "seasoned" and "dry" his wood is.
3: The Old Faithful Technique:
The premise: water becomes visible as it turns to steam.
The technique: toss a sample piece of wood on a briskly burning fire, oriented so the endgrain is visible through the viewing window.
What you're looking for: large amounts of water and steam boiling out of the endgrain for an extended period indicates unseasoned or wet wood.
4: The Satchmo:
The premise: the structure of wood can be compared to a bark-wrapped bundle of tiny tubes made of wood fiber. Moisture in the wood not only fills
the interior of these capillaries, but causes the wood fiber itself to swell, creating an effective barrier to airflow. As the wood dries out the
capillaries open up, and air can pass through more readily.
The technique: mix up some liquid dishwashing detergent with an equal quantity of water, and "paint" one end of the log to be tested. Press your
lips firmly against the other end and blow vigorously, attempting to force air through to the painted end.
What you're looking for: bubbles forming on the soap-painted end indicate airflow through the capillaries, and low moisture content.
5: The Marimba Method:
The Premise: as wood dries out, its acoustical properties change.
The technique: grab two sample pieces of wood at one end and let them dangle, one from each hand. Swing the bottom ends together, and listen to
the sound at impact.
What you're looking for: dry wood will "ring" or "bonk" at impact, as opposed to the dull thud produced by wet wood.
6: Radial Cracks:
The Premise: as fuel wood pieces dry, the wood fiber shrinks, which causes visible cracks to open up on the endgrains.
The technique: examine the ends of a sample piece, looking for cracks that radiate from the core to the bark.
What you're looking for: big, deep radius cracks indicate well-seasoned wood.
Note: this is the least reliable indicator, as the cracks won't close back up if the seasoned wood is subsequently allowed to re-absorb rainwater.
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