Three separate investigations into methods of freeze-drying waterlogged wood, carried out between 1976-1984 at the Museum Conservation Laboratory at the University of Trondheim, focused on those factors which could affect the end result: the species of wood, impregnation with polyethylene glycol before freeze-drying, and the rate of prefreezing before predrying. Objects from the same excavation and treated at the same time by the same methods exhibited different degrees of successful conservation; the studies were undertaken to explain these differences.