Tarnish
Surface discoloration of metal jewelry — especially silver — caused by reaction with sulfur compounds in air, forming dark metal sulfide.
Last updated: July 6, 2026
Detailed Explanation
Tarnish is the gradual darkening occurring on metal jewelry surfaces, most notably silver. The primary mechanism: silver (Ag) reacts with hydrogen sulfide (H₂S) in air to form black silver sulfide (Ag₂S): 2Ag + H₂S → Ag₂S + H₂. This semi-conductive black compound continues growing over time. Tarnish is accelerated by humidity, pollution, contact with rubber, wool, certain foods (eggs, onions), and body sweat. Prevention strategies include rhodium plating (physical barrier), e-coating (polymer coating), anti-tarnish strips in packaging, and lacquer coatings. Tarnish is distinct from corrosion — it affects only the surface and can be polished off, though each polishing removes a small amount of metal.
Common Uses
All silver jewelry, copper-based jewelry, brass jewelry.
Advantages
Natural aging process, some designs intentionally use controlled tarnish for antique/patina effects.
Limitations
Aesthetically undesirable for most consumers, requires maintenance, each polishing removes metal.