VOCABULARY TERM: SANDBLASTED, SANDBLASTING

Sandblasted, Sandblasting. An abrasive blasting process; the pelting of a metal surface with very fine sand to break up a smooth finish. This action produces a matte surface of very low reflectiveness. A tiny individual point of impact with a grain of sand is called a crater, thousands of these would appear in a small area of a medallic surface after sandblasting, also called abrasive blasting. These craters are ideal for processing with a liquid or slurry, as they retain liquid until it forms a chemical reaction with the metal. Sandblasting is often the first step in a medal finishing department because it can accommodate several subsequent steps as metal coloring, relieving, torch finish and such. The process was first developed at the Paris Mint circa 1880. Once the surface is sandblasted it is called matte, or the French term is sablé.

The coarseness of the sand is critical. The finest grain sand was used until shortly after World War II, when more progressive metal manufacturers had turned to glass beads to be able to obtain a finer grit abrasive. This would produce a smoother surface with finer craters while still able to retain liquid. Other abrasive alternatives exist –tumbling and shot peening for example – but these can only be done prior to a piece being struck as a form of metal cleaning.

To read the complete entry on the Newman Numismatic Portal, see:
Sandblasted, Sandblasting (https://nnp.wustl.edu/library/dictionarydetail/516696)

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