In a workpiece processor, a head is moveable onto a bowl to form a process chamber. A workpiece can be cleaned in the processor by immersing the workpiece into a liquid bath in the bowl and then boiling the liquid. Vacuum may be applied to the chamber to reduce the pressure within the chamber, thereby reducing the boiling temperature of the liquid and allowing processing at lower temperatures. In a separate method for prewetting a workpiece, a humid gas is provided into the process chamber and condenses on the workpiece. In another separate method for wetting a workpiece, liquid water is provided into the bowl, with the workpiece above the liquid water. Water vapor is created in the process chamber by applying vacuum to the process chamber. The vapor wets the workpiece. The workpiece is then further wetted by submerging the workpiece into the liquid water.