Conservation Showcase: Naples & Sicily 1791 120 Grano
Posted on 9/6/2010
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All coins are susceptible to the development of dangerous PVC residues. So-called soft flips are commonly used in the numismatic market but are less than ideal long-term storage vessels. Long-term storage in flips containing the plasticizer PVC can allow the chemical to leach out under certain conditions leaving a dulling sticky residue on the surface of the coin they are intended to protect. The green PVC residue can then etch into the surface of a coin leading to irreversible damage.
The large silver 1791 120 Grano coin from the Italian state of Naples & Sicily had suffered with long-term storage in a PVC laden holder. A pale green sticky residue had developed evenly on the surface obscuring the distinctive astronomical design. The conservators at NCS have developed techniques to address this kind of PVC residue while retaining the overall color of the coin. Following conservation, this coin was able to grade numerically with NGC.
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