Category: Tarnish Removal

Chemical Reduction vs Mechanical Abrasion: The Electrochemistry of Tarnish Removal

When silver or base metals tarnish, surface metal atoms combine with ambient sulfur to form a solid compound film (silver sulfide, Ag2S). Traditional polishing pastes operate by abrasive friction: they physically scrape away both the tarnish film and a microscopic layer of the parent metal. Over decades of frequent abrasive polishing, delicate engravings, maker’s hallmarks, and filigree scrollwork gradually flatten and disappear.

Electrochemical tarnish reduction offers a superior non-destructive alternative. By immersing silver in a solution of hot water and baking soda inside an aluminum-lined container, an electrolytic cell is formed. Because aluminum has a higher affinity for sulfur than silver, sulfur atoms migrate from the silver sulfide to the aluminum, converting Ag2S back into pure silver while liberating aluminum sulfide and mild hydrogen sulfide gas. This method reverses tarnish with zero metal loss.