a method of forming metallic structures that consists of immersing shaping dies with a blank workpiece sandwiched between them in a molten metal or alloy bath at a temperature within the superplastic temperature range of the workpiece . the pressure necessary for forming the workpiece is then applied by using weights or other means disposed over the dies . the workpiece is allowed to be formed by the gravitational force of the weights while it is maintained in a superplastic state . a metal or alloy that is free of harmful elements and contaminants that cause damage to the physical properties of the workpiece and that has a melting point below the superplasticity range of the workpiece is suitable for the molten bath . the molten metal serves the dual purpose of displacing all contaminants from the surface of the workpiece and of providing a conductive source of heat for raising the temperature of the workpiece to its superplastic range . because of the contamination - free environment , very high working temperatures are permitted by this process and , correspondingly , relatively low loading pressures are required to achieve the desired deformation ; thus , if necessary , relatively long process times are available for producing exact and intricate configurations that cannot otherwise be successfully obtained .