The appearance of red or pinkish stains on your gold jewelry is a common concern that often leads people to question the metal’s quality. This discoloration is not rust, but rather a form of corrosion known as tarnish. The reddish hue is a chemical reaction involving the non-gold metals intentionally mixed into the jewelry, not the gold itself. Understanding this process helps explain why your possessions seem to change color over time.
The Chemistry Behind Red Discoloration
Pure gold, designated as 22 or 24 karat (24K), is extremely soft and resistant to tarnish because it is a noble metal that does not react easily with oxygen or other elements. To create durable jewelry, pure gold is alloyed, or mixed, with base metals like copper, silver, and zinc to increase its hardness and modify its color. The karat system indicates the proportion of pure gold, with 14K gold containing 58.3% gold and 10K gold containing 41.7% gold.
The red discoloration is caused by the oxidation of the copper content within the alloy. Copper is specifically added to create the warm tones in yellow gold and the distinct pinkish-red of rose gold, but it is highly reactive. When the copper atoms near the surface react with oxygen in the air, they form copper oxide, a compound that presents as a reddish or brownish tint. This explains why lower-karat gold is significantly more susceptible to this type of tarnish.
Environmental and Chemical Triggers
The oxidation process described above is accelerated by specific external factors, primarily exposure to certain chemicals and compounds. Chlorine is a notorious culprit, whether found in swimming pools, hot tubs, or common household cleaning products like bleach. Chlorine can cause the copper alloy to corrode more rapidly, leading to a noticeable red film on the surface.
Sulfur compounds, which are present in the air, can also trigger a reaction with the alloyed metals, forming copper sulfide or silver sulfide that appears as a dark tarnish or reddish spots. Your own body chemistry contributes to the problem, as perspiration contains sodium chloride (salt) and organic acids that react with the copper. Cosmetics, body lotions, and perfumes contain various chemicals that, when in prolonged contact with the metal, can accelerate the formation of this reddish oxide layer.
Cleaning and Prevention Methods
Addressing red tarnish begins with simple cleaning methods you can perform at home to remove the copper oxide layer. A mild solution of warm water mixed with a few drops of dish soap is effective for dissolving the build-up. Gently scrub the jewelry with a soft-bristled toothbrush to reach crevices, followed by a thorough rinse in clean, lukewarm water. For more severe corrosion that does not lift easily, professional cleaning or polishing by a jeweler may be necessary to safely restore the finish.
Prevention is the most effective strategy for maintaining your gold’s luster and avoiding the reappearance of red stains. Always remove your jewelry before swimming in chlorinated water, cleaning with harsh chemicals, or applying cosmetics and perfumes. Proper storage can also minimize tarnishing; keep pieces dry and consider storing them in a lined jewelry box or an anti-tarnish pouch to limit exposure to moisture and air pollutants.