VOCABULARY TERM: RUSTED DIES

Rusted Dies. Since dies are made of ferrous metals they tend to rust in time if their striking surface is exposed to moist atmosphere. Often rust occurs first in the highest part of the die (lowest part of the design on the struck piece), generally in the field around the device, but not exclusively in this position. Rusting causes pits in the die and if allowed to continue this action becomes widespread and deeper. The pitting appears as jagged indentations in the die. Pieces struck from rusted dies – restrikes – will show raised jagged lumps or bosses from the rust pits in the die; these can be removed by chasing.

Preventing rust on dies. Iron rust is caused by chemical attack of moist air, it is essentially hydrated ferric oxide, it usually contains some ferrous oxide and infrequently iron carbonates. Removing air and moisture from the surface of iron will prevent rust. With dies this can be as simple as laying a struck piece tightly against the striking surface. Or by covering the surface, usually the entire top of the die with an airtight cap. Also the top surface can be covered with Cosmolene or petroleum jelly (of course, it must be degreased before additional striking). Dies should be stored with one of these preventative methods in force. Die vaults should be dehumidified as well.

To read the complete entry on the Newman Numismatic Portal, see:
Rusted Dies (https://nnp.wustl.edu/library/dictionarydetail/516694)

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