I am a professional wood turner, producing large (24 in. to 30 in. dia.) enclosed form vessels or bowls. I rough turn them to a 2 in. wall thickness and let them dry for a year before returning them to the lathe for final shape and thickness. I want to try kiln drying them. The opening is only 5 in. in diameter so moisture escape in the inside might be a problem.
I suggest that you contact NYLE in Bangor, Maine for information about their slow drying DH systems. I suspect that you will notice some cracking, however. Have you tried putting them in a freezer? Often this is faster and with no cracks--try one or two and see if you like the results.
Moisture escape should not be a problem as the drying process will be quite slow naturally, allowing the inside moisture to escape.
Professor Gene Wengert is Extension Specialist in Wood Processing at the Department of Forestry, University of Wisconsin-Madison.
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Comment from contributor B:
I turn bowls 6" to 14" in diameter from logs. A member in our club and an article I read suggested using liquid dish soap as a drying method. As stupid as it sounds, both of us have had success with the process and he turns larger diameter pieces. Rough turn as you have, then totally emerse in liquid dish soap. The article suggested leaving the piece in for 48 hours; I've found that the longer you leave it in, the less movement and cracking - 2 weeks has worked well for me. After 2 weeks, remove, drain, and let throughly air dry, about 7 to ten days. Return piece to the lathe, shape, sand, and finish. You might want to try one piece. Problems you might have are finding a container deep enough to hold that amount of liquid and weighting the piece down. 3 weeks to a month is a lot shorter than waiting a year.