Sandblasting
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Sandblasting is a generic term for the process of smoothing, shaping and cleaning a hard surface by forcing solid particles across that surface at high speeds. Sandblasting can occur naturally, usually as a result of the particle blown by the wind causing eolian erosion, or artificially, using compressed air. An artificial sandblasting process was patented by Benjamin Chew Tilghman on October 18, 1870.
In nature, sandblasting of exposed rock surfaces in arid environments can create a dark coating called desert varnish.
Historically, the material used for artificial sandblasting was sand that had been sieved to a uniform size. The silica dust produced in the sandblasting process caused sillicosis after sustained inhalation of dust. Sandblasting may now only be performed in a controlled environment using ventilation, protective clothing and breathing air supply.
Other materials for sandblasting have been developed to be used instead of sand; for example, glass beads, metal pellets, powdered abrasives of various fineness, and even ground coconut shells have been used for specific applications and produce distinct surface finishes.