Pewter is a durable metal alloy used for centuries for items ranging from tableware to decorative objects. It is composed primarily of tin, typically making up 85% to 99% of its mass, combined with small amounts of metals like copper and antimony to increase strength. Despite being a metal, pewter does not rust, which is a direct result of its elemental makeup.
Defining Rust: The Role of Iron
Rust describes a specific type of corrosion, chemically known as iron oxide. This reddish-brown substance forms when a ferrous metal, meaning one containing iron, reacts with oxygen and water through an electrochemical process. Rusting is exclusive to iron and its alloys, such as steel.
Pewter is a tin-based alloy, and modern formulations are free of iron. Because the required ingredient for iron oxide formation is absent, the alloy cannot rust. The corrosion process that affects pewter is a different, much slower chemical reaction that results in a dulling of the metal’s surface. This degradation is cosmetic rather than structural, unlike iron which can crumble entirely due to rust.
Pewter’s True Corrosion: Tarnish and Patina
Pewter is susceptible to tarnish, a mild form of corrosion. Tarnish is the formation of a thin, dull surface layer, often consisting of oxides or sulfides of the tin and copper in the alloy. This layer causes the bright finish of new pewter to darken over time. Patina refers to the desirable, dark-gray coloration that develops uniformly over the years, often preserved by collectors for its antique appearance.
The darkening process is slow and self-limiting, as the oxide layer protects the underlying metal from further deep corrosion. A rare, non-oxidative degradation is “tin pest,” or “pewter rot,” which affects high-tin pewter at extremely low temperatures. This is an allotropic transformation of the tin, causing the metal to change into a brittle, gray powder below 13.2°C. Modern pewter alloys typically include bismuth or antimony, which inhibit this structural change by stabilizing the metal’s crystalline structure.
Simple Care and Cleaning for Pewter Items
Pewter requires minimal maintenance to preserve its finish and prevent excessive tarnish.
Routine Cleaning
The safest method for routine cleaning is hand-washing the item in warm water using a mild dish soap. Use a soft cloth or sponge, as the metal is soft and prone to scratching. After washing, the piece should be immediately dried thoroughly with a clean, soft cloth to prevent water spots. Never place pewter pieces in a dishwasher, as the high heat and harsh detergents can irreversibly discolor and damage the surface.
Polishing and Patina Care
If a piece has a deep, aged patina, it is recommended to only clean it gently without polishing to maintain its historical character. For those who prefer a brighter finish, a polish specifically designed for pewter can be used. Harsh abrasives and silver polish should be avoided to prevent scratching or chemical damage.