Friday, February 17, 2023

Liars figure

Figures don't lie but liars sure can figure.

This is not a trick question: If you have a chunk of green firewood that is 50% moisture and dry it down to 20% moisture, how much moisture did you lose?

Write down your guess.

Let's assume you have a piece of that green wood in your hand and it weighs exactly one pound. Since it is 50% moisture, that means that it is a half-pound of water and a half-pound of anhydrous wood.

Dried to 20% moisture it still has a half-pound of anhydrous wood but now it is down to 0.125 pounds of water.

Yeah, counter-intuitive. The chunk now weighs 0.625 pounds and the water-weight is 0.125.   0.125/0.625 = 20% moisture.

The water-weight dropped from 0.5 to 0.125 pounds or a reduction of 75% of the  original amount of water.

Why is that important?

It is important because when you are burning wood you must first invest heat to bring the chunk up to about 500 degrees before it will catch fire. You must effectively boil off all of that water before the dry-weight starts contributing any heat at all.

To convert water from liquid to vapor gobbles up a huge amount of energy.


  1. That's why you cut wood for next years fire not this years.

    1. Amen to that. Good, seasoned firewood gives more BTU's of heat into the home.

  2. Sort of related. (Retired firefighter.) If I remember correctly, without looking it up, water expands on the order of 1700:1 when converting to steam. That's a big part of why it's so effective in extinguishing MOST fires. Sucks the heat out and displaces the oxygen. (Please don't "fire science" me on this. I know there's more to it, but that's the basics.)

  3. Which is why it is important to buy seasoned fire wood, or let it lie for a year after you cut it yourself.

  4. And burning green wood fouls the chimney much quicker leading to chimney fires. Here in the Great Basin desert I can stack my firewood in May and by October it's dry enough to burn. That's because the relative humidity here in the summer is very low, sometimes less than 10% and the wind blows almost every afternoon. Most places you can't do that.

  5. Saw a fellow doing air layering with two cells of an egg carton folded together and wired closed. Not fumbled with it in years myself. Roger

  6. Cut, split, stacked wood sitting around for 2,3,4,5 years is an invitation for theft, imo.
    Why not just leave felled tree in situ and then cut later (yrs?) when actually needed. Granted, you'd suffer loss due to rot but nowadays rural theft is sky high.
    I think the criminal element is probably using drones for peeking around.

  7. Don't go to a BBQ smoking site & start talking about wood moisture, they'll fight over the best % for smoking food. They get a little carried away.