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robo_hippy
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Drying is an art. Every piece and species of wood is different. General rule is drying too fast the wood cracks. Dry too slow, and the wood molds. Sudden changes in temperature and humidity and the wood cracks. Some times wood just cracks. Cracks can also happen from sanding, usually with dull abrasives at high speed and with a lot of pressure, looks like spider web pattern on the end grain. I don't force dry the wood. Mostly because it takes extra time that could be spend turning more pieces.
So, for bowls, there are two choices, green turn to final thickness, or twice turn: rough out, dry, then return. With green turning, my favorite, turn down to about 1/4 inch thick, round over the rims, wrap the rim in stretch film (woods like maple which have a lot of sugar in them will tend to mold under the film, but are generally easier to dry without cracks). Put in a cool dry spot in the shop on the concrete floor is best. Dry enough to easily sand out in about a week. You will need very slow speeds or the spindle lock to sand them out though, over about 15 rpm, and you can't keep abrasives on the wood.
Twice turning, rough turn to about 10% rule (about 10 inch diameter to about 1 inch thick), round over rims, seal at least the end grain, and off to a cool spot in the shop to dry, 6 months to a year. There are light bulb kilns that will speed up the process, but again that is extra time. Some woods like madrone which warp insanely need to be once turned only or boiled after you rough turn it, then seal and dry. The micro wave does work, but again, that time factor.
With box blanks, I ALWAYS rough turn them, even from kiln dried stock. From KD stock, let sit a month or so to 'adjust' to having the mass removed. From green stock, I let them dry a year or so.
Other than that, "10,000 more times" and you may have better luck.
robo hippy
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