Silver plating applies a thin layer of pure or sterling silver to a foundation made of a less costly metal. This process provides the look and feel of solid silver at a lower price point, but the item’s longevity depends on the outer layer’s durability. Silver-plated items can develop a green discoloration, which signals that the protective silver coating has been compromised. This green substance is not the silver itself, but rather the exposed base metal beneath the plating reacting with the environment.
The Chemistry Behind the Green Color
The appearance of a bright green substance signals that the underlying core is exposed to air and moisture. Most base metals used in plating, such as brass, copper, or nickel silver, contain a high percentage of copper. Copper is a reactive metal that easily undergoes corrosion.
When the thin layer of silver plating is worn away by friction or scratches, the copper-rich base metal contacts oxygen, humidity, and mild acids, such as those found in human sweat. This reaction forms various copper salts, primarily copper carbonate, commonly known as verdigris. Verdigris is the distinct blue-green compound responsible for the color change seen on aged copper structures.
Standard silver tarnish is a dark gray or black film of silver sulfide, which forms when silver reacts with sulfur compounds in the air. The green color, by contrast, is a clear indication of base metal corrosion, not superficial silver tarnish. The thinness of the silver layer means that once that barrier is breached, the susceptible base metal quickly begins to form the green patina.
Silver Plate vs. Solid Silver: Understanding Material Differences
The structural difference between silver-plated items and solid silver, such as sterling silver, explains why plating is more prone to turning green. Silver plating involves a microscopic layer of silver bonded to a core of a different, non-precious alloy. This plating layer is often measured in micrometers and can wear away over time, exposing the reactive core.
Sterling silver is an alloy of 92.5% pure silver and 7.5% other metals, typically copper, which is mixed throughout the material. While the copper content can react to form a minor green stain on the skin under certain conditions, the piece itself does not turn green. Because the copper is alloyed throughout the entire mass, the surface reaction remains minimal and is quickly overwhelmed by the characteristic black tarnish of silver sulfide.
Preventing the Base Metal Reaction
Preventing the green reaction focuses on protecting the integrity of the silver plating and limiting the base metal’s exposure to corrosive agents. Since the plating is the only barrier, careful handling is necessary to avoid physical abrasion. Avoid using abrasive cleaning cloths, harsh chemical dips, or aggressive polishing, as these can quickly strip away the thin silver layer.
Moisture is a major accelerator of the corrosion process, so silver-plated items should be removed before bathing, swimming, or engaging in activities that cause heavy perspiration. Avoid contact with cosmetics, lotions, and perfumes, as their chemical ingredients can attack the plating. Always wipe the item clean with a soft, lint-free cloth after wear to remove skin oils and moisture before storage.
Proper storage is another practical step in prevention. Items should be stored in a cool, dry place, ideally in an airtight bag or container with an anti-tarnish strip or a packet of silica gel to absorb humidity. If the plating is significantly worn and the base metal is exposed, professional replating is a restoration option. This involves reapplying a fresh layer of silver through an electroplating process, renewing the protective barrier and extending the item’s life.