A Homemade Solar Lumber Kiln

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And there's another, more subtle, bonus to using a solar drying kiln: Since the lumber can be placed inside the structure as soon as it's milled, the planks remain free of the sand and dirt that almost certainly would accumulate on them if they were stored outside . . . and that sort of grit is murder on cutting tools.

IN RETROSPECT

The lumber I've dried during the two years that my solar kiln has been in operation has proved to be of outstanding quality and durability . . .it's beautiful to look at and a joy to work with.

Better yet, the kiln's total operating cost has averaged about $10 a month (for electricity for the two fans), and the entire process all but takes care of itself. I just stack the green lumber in the kiln, check occasionally to be sure the thermostats and fans are performing as they should, and take the lumber out when it's dry.

In summary, I've found it quite satisfying to hop on the sun-power bandwagon in my own little way. My simple solar kiln has taken me a bit further along the golden road to self-sufficiency.

Measuring The Moisture Content of Lumber

I know of two ways to determine the moisture content of lumber. The first (which is used primarily in laboratory situations) requires five steps: [1] Weigh a sampleof the wood to be measured, [2] place the sample in an oven and carefully bake out all the moisture, (3] weigh the dried sample, [4] subtract the weight of the dried sample from its wet weight, and (5] use the difference to calculate the percentage of moisture in the original sample.

(This final step may need same clarification. Let's say the green sample weighs 20 ounces . . .and after drying, it weighs only 16 ounces. That means 4 ounces ofwater was baked out of the wood. Now that 4 ouncesof water weight represents one fifth, or 20%, of the weight of the green wood. The moisture contentof the original sample, then, was 20%.)

The second method of determining the moisture content of wood is much simpler—but not nearly so inexpensive—as the oven technique. It requires the purchase ofan electronic moisture tester.

I bought one of the gadgets a couple ofyears back, and it cost more than my entire kiln . . .about $230. But I do dry valuable woods on a relatively large scale, so I felt that the gauge was a worthwhile investment (after all, it's nice to know for sure when the drying process is complete).

There are several models of electronic moisture testers on the market today, but here's how mine works: Two metal prongs (actually, they're electrodes) are drivenabout an inch into the wood sample. An electrical current is then introduced through one electrode. It travels through the wood, is picked up by the second prong, and is sent to the tester to be measured. The water in the wood sample transmits the electricity from one electrode to the other . . . so the more moisture in the lumber, the more juice will get through.

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