Hold the sandcarving gun 6 to 8 inches away from the object you are sandcarving perpendicular to its surface. The recommended maximum pressure for a pressure pot sandcarve system is 25 to 35 psi using a pressure pot sandcarving machine. Sandcarving abrasive size should range from 180 to 220 depending on the detail of the image and type of substrate. Typically, 180 to 220 abrasive is used on glass, crystal, ceramic, and metal, while 150 is preferred on stone or marble and occasionally wood products. The recommended abrasive media is either silicon carbide or aluminum oxide.
—Michael Sullivan, IKONICS Imaging