NCS Conservation: The Challenges of Copper

Numismatic Conservation Services™ (NCS®) uses a variety of proprietary techniques to remove harmful surface contaminants, stabilize and protect a coin's surfaces and, in many cases, improve a coin's eye appeal. After coins are conserved by NCS, they are seamlessly transferred to Numismatic Guaranty Company® (NGC®), an independent affiliate of NCS, for grading and encapsulation. Below are a few highlights of coins that were conserved by NCS and graded by NGC recently.

Among the most frequently used metals for coinage, copper is arguably the most reactive to the immediate environment. Given this property, coins with high copper alloy present both specific issues and requirements when it comes to their professional conservation. This bronze 1868 2 Cents was recently submitted for NCS conservation to address the matte residues completely covering both sides and darker build up in the recesses of the design, particularly on the reverse.

Residues like what is seen here are commonly found on vintage bronze coins. While copper alloy coins can be sensitive to physical changes based on their immediate environment, they can also be highly sensitive to damage due to improper conservation attempts. Careful removal of the surface residues on this 2 Cent coin was able to reveal a pleasantly brown-toned coin free of permanent environmental damage. This coin was able to grade with NGC following conservation.

US 1868 2 Cents Before conservation Click images to enlarge.
US 1868 2 Cents After conservation Click images to enlarge.

Despite their more golden hue, coins made of an aluminum bronze alloy often behave much the same as other bronze coins during decades of poor storage. This Germany 1923F 5 Pfennig was submitted to address the mottled green and brown residues covering much of the surfaces. Heavy residues such as what was seen here can often cause permanent damage in the form of corrosion. With careful conservation work, this copper alloy piece coin was revealed to be lustrous with a rich golden coloring. Following professional conservation, this coin was able to grade well with NGC.

Germany 1923F 5 Pfennig Before conservation Click images to enlarge.
Germany 1923F 5 Pfennig After conservation Click images to enlarge.

Poor long-term storage methods can cause potentially damaging residues. This proof bronze South Africa 1923 Penny was recently submitted to NCS to remove an opaque white residue hiding lustrous surfaces underneath. Advanced residue development like what is seen on this South African bronze can lead to permanent corrosion damage. Luckily for this important bronze coin, once all residues were carefully removed, it was able to grade well with NGC.

South Africa 1923 Penny Before conservation Click images to enlarge.
South Africa 1923 Penny After conservation Click images to enlarge.

For more information about NCS, visit NGCcoin.com.