A method of thermally shaping individual sheets of glass for the International X-Ray Observatory using porous mandrels as air bearings has been developed, which eliminates the problems of sticking and dust particleinduced distortion which plague traditional slumping methods. A detailed mathematical model of the process has been developed, allowing prediction of final glass shape based on process parameters that include air supply pressure, imperfections on the mandrel surface, glass total thickness variations and gravity vector orientation. Experiments to verify model findings are conducted under closed-loop control of pressure and apparatus tilt. Little improvement in repeatability is seen, suggesting that the error is due to unmodeled forces such as contact forces from the glass holding technique. Finally, the design process and fabrication of a third generation slumping tool is presented. In addition to scaling the design to accomodate larger flats, slumps are done horizontally to float the glass and minimize contact during the process. New capabilities of the tool include active gap measurement and control, as well as plenum air temperature monitoring.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.