Turning Archive

Moisture content by oven-dry method *PIC*

John K Jordan
I got some waxed 1" square Ebony blanks from Pete Kekel (Big Monk Lumber in KY) with unknown moisture content. Waxed wood blanks can be anywhere from green to dry and I find it difficult to guess with hard exotics. My pinless moisture meter needs a bigger contact area so I decided to use the oven-dry method which gives the absolute moisture content independent of the density of the wood. This method is always accurate and cheap if you already have the simple equipment on hand.

If not familiar with this, basically a wood sample is first weighed then gently dried in an oven and weighed repeatedly until the weight quits changing. Then subtract the dry weight from the wet weight to get the water weight and divide that by the dry weight to get the moisture content.

I cut away the surface wax and cut samples from one of the Ebony blanks. A toaster oven dried the wood. I put a thermocouple in the oven to monitor the temperature which needs to be between 212 and 220, ideally 217. The little digital scale is good to 0.1 grams (checked with my triple-beam balance).

Since I couldn't watch it all the time I put the toaster oven on the concrete floor in my shop office to keep it away from combustibles. I checked the temperature every few hours and quit when the weight was unchanged over two readings.

The moisture content of this Ebony was just over 13% which matched the expected equilibrium MC of air-dried lumber in both TN and KY. It's good to know I can turn these without further drying.

If interested in more detail: https://ir.library.oregonstate.edu/downloads/jm214q048


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Moisture content by oven-dry method *PIC*
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