Moisture Testing Without a Meter?

[Grgramps]

Yesterday I bought a rough sawn pine board 4/4 X 10" X 16' from a local sawmill and was told it was dry. (I don't have a meter). Today I started to build a box to hold the Jenga blocks: http://www.ncwoodworker.net/forums/showthread.php?t=4879&highlight=jenga and got that uneasy feeling that this wood wasn't dry. The idea of putting a piece in the microwave came to me, so I placed several cigarette pack size blocks in at 50% for 3 min. These were sealed in a plastic storage bag and halfway through the cycle, the bag went poof which didn't surprise me. At 3 min the blocks were quite warm and the bag was very wet inside. Not a good sign.
Then I wondered what a piece of wood that's been dried and has been in the shop a couple of years would do. I gathered a few dry scraps and stood them on end in the MW with a piece of the pine. This time the top end of the pine started to bubble as the moisture exited. Other pieces got warm, some hot, but no evidence of moisture. Obviously, this wood should dry some more, but I wonder if there is a simple way for me to tell when this $7 piece of wood is dry without buying a moisture meter? What I am intending to build is nothing more than a toy box, so this isn't critical. Any ideas?
Roy

 

[PeteM]

I've never tried it but read you can do it by weight. Weigh it - Wait - Weigh it again . . .
It will get lighter as it dries. When it stops getting lighter is as dry as it's gonna get.

pete

 

[woodguy1975]

Exactly what Pete said. If you have a postage scale or some light weight scale you can test dry a sample. Weigh it before you start and after a couple cycles in the microwave. If your weight is changing then it isn't dry.

Good Luck,

John

 

[chris99z71]

If you're doing a relatively small sample, you're going to need a pretty accurate scale.
According to this site Calculation of density with wood, a 2" cube (8 cubic inches) only wieghs about 2.728 ounces (77.3 g). Therefore to detect a 1% change in moisture content, you're going to need a scale accurate to 0.02 ounces (0.7 g) - not something that you're going to do with the bathroom scale unless you use a pretty big sample. BUT if you have a scale that accurate, I'd suspect that this technique is as accurate as any other.

Edit: Out of curiosity, I looked up some postage scales and most of them only have about 0.1 oz./1g accuracy. So to detect a 1% change, you'd need to start with a 10 oz (284g)sample - that would be about a 3" cube.

 

[PeteM]

To find an accurate scale make friends with a drug dealer or a print shop owner :lol::lol::lol:

I don't know of any drug dealers in the area but our pressman has a scale that's accurate to 1 tenth of a gram (used for mixing ink colors).:eusa_dancThink I'll see if I can borrow it over the weekend for a little experiment.

pete

 

[Grgramps]

Hey Guys, I appreciate your interest and you've helped me jog the old grey cells into activity. We have a Tanita bath scale that has proved to be VERY accurate. I have cut a piece about 5' in length and planed to a smooth surface (over 3/4" thick). It weighs 5.8 lbs and the dehumidifier in the shop is running. I'll watch it, and when the weight quits falling, I will assume that it's dry enough for my use.
I found planing this wood a new experience. (Never planed pine before.) The wood coming out of the planer looked like what you would see in a paper shredder. It was in pieces as long as 4 inches! Might have gone unnoticed except that it clogged the dust collector. It didn't want to pass the webbing at the intake that is there to keep large objects from passing. Like hair in the shower drain. (Not that I have much of that left.) Every day is a new experience.
Thanks again for the suggestions.
Roy

 

[gator]

One thing to watch for in drying via microwave. Make sure that the sample you use (if you go the sample route) has the same bulk (thickness, width) as the primary piece. A small sample (ie: 2 x 2 x 1) will dry much quicker than a 2 x 8 x 2'.

George