Diatomaceous Earth Insulation Mining, Milling and Manufacture, 1962

Diatomaceous Earth Insulation Mining, Milling and Manufacture, 1962

Diatomaceous earth, also known as diatomite or kieselgur, is a naturally occurring, soft, siliceous sedimentary rock that is easily crumbled into a fine white to off-white powder. This powder has an abrasive feel, similar to pumice powder, and is very light, due to its high porosity. Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled algae. It is used as a filtration aid, as a mild abrasive, as a mechanical insecticide, as an absorbent for liquids, as cat litter, as an activator in blood clotting studies, and as a component of dynamite. As it is also heat-resistant, it can be used as a thermal insulator, especially in high-temperature applications such as furnaces and boilers, as described in this film clip. In the United States, large deposits of diatomite are found in California, Nevada, Washington and Oregon. Of these states, California and Nevada produce the largest amount of diatomite. Significant producers of diatomite worldwide include France, China, Denmark, Russia, and Algeria. The hazards to worker is breathing dust deep into the lungs which can cause scarring of delicate gas exchange tissue and lead to silicosis. The lungs become less flexible, making it difficult to breathe and do hard work. Once silicosis develops, the damage is permanent. Breathing silica dust can also cause lung cancer and increase the chance of developing tuberculosis. For more on the hazards of silica and how to prevent them, go to http://www.cdc.gov/niosh/topics/silica/ . This clip is from the 1962 film, Heat and Its Control, from the U. S. Bureau of Mines, in cooperation with the Johns Manville Corporation. The film is about the importance of controlling heat, chronicles man’s use of heat-energy sources and explains radiation, convection, and conduction heat transfer. The film shows heat insulation production from magnesia, rock-wool, asbestos and celite (diatomaceous earth). The entire film is available at the US National Archives in Maryland.