Here is some information I've found that was useful to me. There seems to be three methods of vacuum drying. 1. Cyclic temperature and vacuum (used by commercial dryers) 2. Constant vacuum with fresh air intake using heated shelves 3. Constant vacuum using ambient heat (as in the article below). All methods seem to use 15-18mm Hg vacuum. Dan
A technical description of the process from VacuTherm
formatting link
From the Forest Products Journal (not from the FPL): VACUUM DRYING OF SMALL WOOD COMPONENTS AT ROOM TEMPERATURE
formatting link