Phase 1: Initial Vacuum The pile of wood, once positioned on the powered trolley of the autoclave, is placed inside the plant to start the cycle. The hermetic closing of the door enables the machine to begin treatment by starting the vacuum pump. This phase, which is very important for the success of the cycle, frees the pores of the wood of air, by generating a "vacuum" which will allow the wood "to breathe" in the preserving solution. The length of the vacuum phase can vary from 30 to 90 minutes according to the characteristics of the wood.