Yes, 9ct gold can tarnish, appearing as a darkening or dulling of the metal’s surface. This reaction is a direct consequence of its composition, as 9ct gold is not pure gold. The karat system measures gold purity; 24ct is 100% pure gold, meaning 9ct gold is only 37.5% pure gold. The remaining 62.5% consists of other metals added to increase durability and reduce cost. This high proportion of non-gold metals makes 9ct gold susceptible to tarnish.
Why 9ct Gold Tarnishes: The Role of Alloying Metals
The reason 9ct gold tarnishes is rooted in the metals mixed with it to create the final alloy. While pure gold is a noble metal that resists reaction with oxygen and most chemicals, the other metals used in the alloy are highly reactive.
The primary culprits are copper and silver, commonly used to create the yellow gold alloy. Tarnish forms when these base metals react with compounds found in the environment. Copper and silver are susceptible to both oxidation and sulfidation, corrosive reactions that form a dark surface film.
Oxidation occurs when the non-gold metals react with oxygen and moisture in the air, creating dull metal oxides. Sulfidation is often a more significant factor, where silver and copper react with airborne sulfur compounds, such as hydrogen sulfide, to form dark metal sulfides. The high percentage of base metals in 9ct gold accelerates this process compared to higher-karat gold.
Environmental and Contact Factors That Accelerate Tarnish
While the alloy’s composition makes tarnish possible, external factors determine how quickly the discoloration appears. Daily exposure to moisture and high humidity significantly speeds up chemical reactions, as water acts as a catalyst for oxidation and sulfidation. Air quality also contributes, especially in areas with high pollution or airborne sulfur.
Direct contact with personal care products and household cleaners introduces potent chemicals that accelerate tarnish. Chlorine, found in cleaning solutions and swimming pools, is particularly corrosive to the alloy metals. Cosmetics, lotions, and perfumes also leave residues that trap moisture and foster chemical reactions.
Natural skin secretions, such as sweat, also play a role because they contain salts, oils, and fatty acids. These substances interact directly with the metal surface, creating an acidic or salty film that breaks down the alloy faster. Even natural oils transferred from handling the jewelry can build up, allowing dirt and reactive compounds to settle and begin discoloration.
Preventing Tarnish and Restoring Luster
Preventing tarnish relies on reducing contact between the reactive alloy metals and external chemical accelerators. Proper storage is effective, minimizing exposure to moisture and airborne sulfur. Jewelry should be stored in a cool, dry place, ideally within an airtight container or a jewelry box lined with anti-tarnish fabric.
Developing careful wearing habits will slow the rate of discoloration. Put 9ct gold jewelry on last, after applying perfumes, hairsprays, and lotions, and take it off first. It is also important to remove the piece before:
- Swimming
- Showering
- Exercising
- Using household cleaning products
Regular, gentle cleaning is essential for maintaining luster and can be done at home. Prepare a mild solution of warm water and a few drops of non-detergent dish soap in a bowl. Soak the jewelry for five to ten minutes to loosen accumulated oils and dirt.
After soaking, gently scrub the piece, paying attention to crevices and settings, using a new toothbrush with very soft bristles. Scrub lightly to avoid scratching the softer gold alloy surface. Rinse the jewelry thoroughly under clean, lukewarm running water to remove all soap residue.
Immediately dry the piece with a soft, lint-free cloth, avoiding abrasive paper towels. Once dry, use a specially treated jeweler’s polishing cloth to gently buff the surface, which removes light tarnish and restores shine. For heavy, stubborn tarnish, consulting a professional jeweler for ultrasonic cleaning or light polishing is the safest way to restore the metal.