Gold, a metal revered for its enduring luster and value, is often associated with permanence. To understand if gold tarnishes, distinguish between pure gold and the alloys commonly found in jewelry. Pure gold itself does not tarnish, but jewelry often appears discolored due to reactions involving the other metals mixed with gold. This apparent tarnish on gold jewelry is common, prompting questions about its causes and prevention.
Why Pure Gold Resists Tarnish
Pure gold, also known as 24-karat gold, possesses an inherent resistance to tarnish due to its chemical properties. Gold is classified as a “noble metal,” meaning it exhibits exceptional stability and does not readily react with oxygen or most other elements found in the environment. Its atomic structure makes its outer electrons less available for bonding with elements like oxygen or sulfur. This stability prevents it from undergoing oxidation, the chemical process that leads to tarnish.
Unlike iron or copper, which readily form oxides when exposed to air and moisture, gold’s atoms resist bonding with these common environmental elements. This chemical inertness ensures that pure gold maintains its brilliant, untarnished appearance over extended periods. Even after centuries, pure gold can retain its original sheen, a quality that makes it highly prized for its aesthetic appeal and durability.
What Causes Gold to Appear Tarnished
While pure gold is chemically inert, gold jewelry typically consists of alloys—mixtures of gold and other metals like copper, silver, or zinc. These additional metals enhance the gold’s durability, as pure gold is too soft for most jewelry applications. It is these less noble metals within the alloy that react with environmental factors, leading to the appearance of tarnish.
Exposure to sulfur compounds is a primary cause of apparent tarnishing. Sulfur is present in the air, some foods, and certain cosmetics. When copper or silver in gold alloys contacts sulfur, it forms sulfides, which appear as a dark or dull layer. This reaction results in discoloration, often dark brown or black.
Chlorine, commonly found in swimming pools and household cleaning products, is another culprit. It reacts with base metals in gold alloys, such as copper and silver, causing corrosion and discoloration. Prolonged exposure can weaken the jewelry’s structural integrity. Even small amounts of chlorine in tap water can contribute to this effect over time.
Everyday substances and bodily secretions also contribute to this perceived tarnish. Cosmetics, perfumes, hairsprays, and lotions contain chemicals that react with alloyed metals. Body oils and sweat, which contain salts and acids, also cause chemical reactions that lead to discoloration, particularly in lower karat gold. The extent of this reaction often depends on an individual’s skin chemistry and the amount of sweat produced.
Caring for Your Gold Jewelry
Proper care and maintenance can help prevent your gold jewelry from appearing tarnished and maintain its luster. Storing jewelry correctly is a key preventive measure; keep it in a cool, dry place away from direct sunlight and humidity. Using individual soft pouches or a jewelry box with separate compartments can prevent scratching and minimize exposure to air and moisture. Anti-tarnish strips or silica gel packets can also be placed in storage containers to absorb moisture and harmful gases.
Removing gold jewelry before engaging in certain activities is beneficial. Take off jewelry before swimming in chlorinated pools, cleaning with harsh chemicals, or applying cosmetics, lotions, and perfumes. This minimizes contact with substances that can react with the alloyed metals and cause discoloration. Removing jewelry before exercising can also help prevent tarnishing from sweat and body oils.
For cleaning, gentle methods are recommended. A solution of warm water and a few drops of mild dish soap can effectively remove dirt and oils. Soak the jewelry for 10-20 minutes, then gently scrub with a soft-bristled toothbrush to loosen and remove buildup. Rinse thoroughly with clean water and dry completely with a soft, lint-free cloth to prevent water spots. For heavily tarnished pieces or those with delicate gemstones, consulting a professional jeweler for cleaning is often the safest approach.