Silver has been valued for centuries, gracing everything from heirloom tableware to modern jewelry. This metal is prone to a dark discoloration commonly known as tarnish, which often leads people to believe that water itself is damaging the silver. Understanding the true cause of this change is the first step in preserving silver’s bright appearance. The question is not whether silver changes color when it gets wet, but rather what is carried in the water that initiates the chemical process.
The Chemical Inertness of Silver and Pure Water
Pure silver is classified as a noble metal, meaning it exhibits a high resistance to chemical action, corrosion, and oxidation. This inherent stability means that pure, distilled water, which is chemically neutral, will not cause silver to change color or tarnish at normal temperatures. The metallic element (Ag) does not readily react with the oxygen found in the water molecule (\(\text{H}_2\text{O}\)). Therefore, if silver is exposed only to deionized or distilled water, it should remain untarnished. Water is not inherently corrosive to silver, but it is an effective vehicle for other compounds.
How Contaminants in Water Trigger Tarnish
The discoloration commonly observed on silver is a reaction with contaminants that water carries or introduces to the metal’s surface. The most frequent cause of tarnish is the formation of silver sulfide (\(\text{Ag}_2\text{S}\)), a dark compound that appears gray, yellow, or black. This reaction occurs when silver interacts with sulfur compounds, such as hydrogen sulfide, which are present in the air and frequently dissolved in water supplies.
Water, especially tap water, contains dissolved minerals and gases that act as catalysts for tarnish. Water acts as an electrolyte, facilitating the movement of reactive sulfur ions onto the silver surface, which significantly speeds up the chemical reaction. Moisture accelerates the process, meaning silver stored in a high-humidity environment will tarnish faster.
Beyond sulfur, other waterborne contaminants cause discoloration. Swimming pool water and hot tubs contain chlorine, a powerful halide that reacts aggressively with silver. This exposure forms silver chloride, a compound that appears white, gray, or dark, and can accelerate corrosion and pitting. Saltwater is corrosive due to its high chloride concentration, which speeds up deterioration.
Practical Steps for Preventing and Reversing Discoloration
Prevention
Preventing tarnish involves minimizing silver’s contact with the environmental compounds that trigger the chemical reaction. It is advisable to remove silver jewelry before showering, swimming, or engaging in activities where it will be exposed to chlorinated or saltwater. After any accidental exposure to water, the silver should be immediately and thoroughly dried with a soft, lint-free cloth to remove moisture and contaminants.
Proper storage is another effective preventive measure, focusing on reducing exposure to humidity and sulfur-containing air. Silver items should be kept in airtight containers, zip-top plastic bags, or tarnish-resistant cloth pouches designed to limit gas exchange. Adding anti-tarnish strips or packets of silica gel to the storage area can further absorb moisture and sulfur compounds, slowing the rate of discoloration.
Reversal
To reverse existing tarnish, a simple and effective method is the electrolytic cleaning process using household items. This technique involves placing the tarnished silver in a bowl lined with aluminum foil, shiny side up, and covering it with hot water and a few tablespoons of baking soda. The chemical reaction transfers the sulfur from the silver onto the aluminum foil, converting the silver sulfide back into metallic silver. For light discoloration, a gentle scrub with a soft cloth and warm water mixed with a few drops of mild dish soap can safely restore the metal’s shine.