.925 silver, known as Sterling Silver, does tarnish. It is an alloy composed of 92.5% pure silver and 7.5% other metals, typically copper. This blend is necessary because pure silver is too soft for practical use. While copper improves the metal’s strength, its inclusion makes the alloy susceptible to tarnish. Tarnish presents as a dulling or darkening of the surface, which is a natural chemical reaction.
Understanding the Tarnish Reaction
Tarnishing is a surface corrosion process, often incorrectly called oxidation. The process is primarily a reaction with sulfur-containing compounds in the atmosphere, not just oxygen. When silver is exposed to airborne substances like hydrogen sulfide, a chemical reaction occurs. The resulting dark, discolored layer is silver sulfide, formed when silver reacts with sulfur.
The small percentage of copper in the .925 alloy accelerates this reaction because copper also reacts with atmospheric elements. Environmental factors like high humidity, air pollution, and natural oils from human skin can speed up the rate at which silver sulfide forms. Since sulfur compounds are present in everyday items, tarnish is an inevitable process requiring proactive management.
Strategies for Preventing Tarnish
Proactive storage and careful wearing habits are the most effective ways to slow down tarnish formation. Since exposure to air and humidity accelerates the chemical reaction, store silver in a cool, dry environment. Specialized airtight bags or containers lined with anti-tarnish fabric help block the sulfur compounds that cause darkening. Adding anti-tarnish strips or silica gel packets further absorbs moisture and sulfur.
Follow the “last on, first off” rule for silver jewelry: put it on after applying beauty products and remove it first. Perfumes, lotions, and makeup often contain chemicals that accelerate tarnishing. Always remove silver items before swimming, showering, or using household cleaning products, as chlorine is particularly damaging. Wiping silver pieces with a soft cloth after wearing them helps remove surface residue before storage.
Effective Tarnish Removal Methods
Once tarnish has formed, several methods can safely restore the metal’s luster.
Mechanical Polishing
For light discoloration, mechanical polishing using a specially treated silver polishing cloth is the simplest method. These soft cloths are impregnated with a mild chemical that gently rubs away the thin silver sulfide layer without scratching the surface.
Chemical Immersion
For pieces with significant tarnish or intricate designs, chemical immersion is highly effective. The aluminum foil and baking soda bath is a popular home remedy utilizing an ion exchange process. To perform this, line a bowl with aluminum foil and place the silver inside, ensuring contact. Adding hot water, baking soda, and salt creates an electrochemical reaction where the aluminum attracts the sulfur from the silver sulfide, reversing the tarnish onto the foil.
Commercial liquid dips and pastes offer a fast chemical solution, but caution is necessary when using them on items with soft or porous gemstones like turquoise or amber. Another gentle home cleaning solution involves mixing a paste of two parts baking soda to one part water and gently rubbing it onto the tarnished areas. After any cleaning process, rinse the silver thoroughly with cool water and dry it immediately with a soft, non-abrasive cloth to prevent water spots.