An effective means of extinguishing magnesium incendiary bombs with ground feldspar or feldspar-rich rock has been announced by the United States Geological Survey, Department of the Interior, Washington. The effectiveness of the method has been demonstrated at the Geological Survey laboratories and at the Edgewood Arsenal of the Chemical Warfare Service. The United States Government controls the patent to protect the public interest against price exploitation and misleading or extravagant claims by private companies. Under the patent, the process and use of the material will be made available to any commercial concern.

Feldspar or rock composed largely of feldspar is ground to pass a 10-mesh screen and to be retained by a 200-mesh screen. This ground material may be spread on burning or molten magnesium, the heat of which (about 3300 degrees Fahrenheit) quickly melts the substance (melting point about 2100 degrees Fahrenheit) to form a protective coating that cuts off the supply of oxygen in the air and actually stops the magnesium from burning and its flame from spreading. After the ground feldspar or rock has been applied, the bomb requires no further attention, but a supply of water must be available to extinguish fires started by flying sparks.

Removal of extra-fine material of less than 200-mesh screen size from the ground product is essential because such fines tend to clog interstices that permit the ready escape of gases; otherwise, the gases will erupt with sufficient violence to form miniature craters in the feldspar cover and impair or destroy its effectiveness.