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Salt Cellar
Date: Late 19th - Early 20th Century Artist: Unknown Materials: Nickel plated lead alloy Dimensions (cm): 4.3 (height) x 9.4 (diameter) Institution/Owner: Independence Seaport Museum Key Treatment Steps
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Summary
This small metal bowl was identified by the Independence Seaport Museum in Philadelphia as a salt cellar. It is understood to be associated with the USS Olympia, a protected cruiser used by the US Navy between 1895 and 1922. The museum had previously thought this to be a silver plated object, however pXRF analysis I conducted revealed that the object is in fact a nickel-plated lead alloy.
The salt cellar was in fair structural condition, with some loss to the nickel plating (primarily on the interior). White corrosion products (which I identified as lead carbonates using XRD) and a black grimy material were present on the surface of the nickel plating and in some areas of the exposed base metal in the interior.
The black grimy material was easily removed via a combination of mechanical and solvent cleaning using 1:1 acetone:ethanol. The lead carbonates were more difficult to remove, as they generally insoluble in all but acidic or basic solutions. Following testing, 10% sodium hydroxide was identified as the most effective cleaning agent.
Following the removal of lead carbonates and dark grime, both the interior and exterior surfaces were lightly polished. The soft, exposed lead-alloy on the interior was polished with a fine pumice slurry, and the hard nickel plating was polished with an alumina slurry.
This small metal bowl was identified by the Independence Seaport Museum in Philadelphia as a salt cellar. It is understood to be associated with the USS Olympia, a protected cruiser used by the US Navy between 1895 and 1922. The museum had previously thought this to be a silver plated object, however pXRF analysis I conducted revealed that the object is in fact a nickel-plated lead alloy.
The salt cellar was in fair structural condition, with some loss to the nickel plating (primarily on the interior). White corrosion products (which I identified as lead carbonates using XRD) and a black grimy material were present on the surface of the nickel plating and in some areas of the exposed base metal in the interior.
The black grimy material was easily removed via a combination of mechanical and solvent cleaning using 1:1 acetone:ethanol. The lead carbonates were more difficult to remove, as they generally insoluble in all but acidic or basic solutions. Following testing, 10% sodium hydroxide was identified as the most effective cleaning agent.
Following the removal of lead carbonates and dark grime, both the interior and exterior surfaces were lightly polished. The soft, exposed lead-alloy on the interior was polished with a fine pumice slurry, and the hard nickel plating was polished with an alumina slurry.
Treatment Images
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