A process for dewaxing a mold for use in lost wax casting is proposed, wherein the mold is loaded on a pallet which is placed and then securely held on a carrier which is rotatably assembled in a dewaxing tank. The mold is inverted to be ready for dewaxing within the tank and then returned to the initial condition within the tank by rotating the carrier by about 180 degrees at a time.An autoclave for use in the process comprises a carrier framework rotatably disposed within a dewaxing tank for carrying a pallet loaded with shell mold trees. The carrier framework is held in a first position for assembling the pallet and then is rotated by about 180 degrees to a second inverted position to hold the pallet securely in the inverted condition during the dewaxing operation.A preferred embodiment of the autoclave further comprises means for securely fastening the pallet and the mold trees automatically and simultaneously with the operation of sealingly closing the entrance opening of the dewaxing tank.