Seventy-nine years on a hand, and the metal has not changed at all. That is 18K doing what gold does. Wedding Band, 18K gold, Sweden, 1946
Gold does not tarnish. That is not a marketing claim, it is chemistry: gold does not react with oxygen or with the sulphur compounds in air, which is why gold objects come out of the ground after three thousand years looking like gold. So when a gold chain goes dull or leaves a dark line on the skin, the gold is not the thing that changed. Everything else in the alloy is.
What is actually in your gold
Pure gold is too soft to wear, so it is alloyed with other metals for hardness and colour. Those metals do react. Copper oxidises and darkens. Silver reacts with sulphur and blackens. Nickel and zinc corrode slowly. The lower the karat, the more of them there is.
| Karat | Gold content | Other metals | Tendency to darken |
|---|---|---|---|
| 9K (375) | 37.5% | 62.5% | Noticeable, especially in humid climates |
| 14K (585) | 58.5% | 41.5% | Slight over years |
| 18K (750) | 75% | 25% | Very slight |
| 22K (916) | 91.6% | 8.4% | Effectively none |
This is the practical reason so much antique Scandinavian and Middle Eastern jewelry was made high karat, and why a 23K Swedish band from 1900 still glows while a 9K English chain from 1970 can look tired. The trade-off is softness, which is the argument laid out in 14K vs 18K gold.
The four things that cause it
Sulphur in air, in some tap water, in eggs and onions, and in a great many cosmetics. It attacks the silver in the alloy.
Chlorine, which is the serious one. Swimming pools and bleach attack the copper and silver in gold alloys directly, and repeated exposure does not just discolour the surface, it weakens the metal at the grain boundaries. Chains have snapped because of it. This is the main reason for the advice in can you shower with gold jewelry.
Skin chemistry. Sweat is salty and mildly acidic, and it varies enormously from person to person and with medication, diet and hormones. Two people can wear identical chains with completely different results.
Cosmetics and cleaning products. Hand sanitiser, hairspray, foundation and household cleaners all contain compounds that dull the surface. Most of what people call tarnish on gold is actually a film of accumulated residue rather than a chemical change at all.
Fifty-five grams of Danish 14K from 1960. Lower karat means more copper in the mix, and it still looks like this. Danish Vintage Necklace, 14K gold, 55 grams, 1960
How to fix it
Almost always with warm water, a drop of washing-up liquid and a soft toothbrush, followed by a thorough rinse and a proper dry. That removes the residue film, which is what most dullness is. For anything more stubborn on plain gold with no stones, a gold polishing cloth will restore the shine.
What not to do: do not use silver dip, which is formulated for a different metal and attacks gold alloys. Do not use an ultrasonic cleaner on anything with closed settings, foiled stones, pearls, opals, emeralds or enamel, for the reasons in the cleaning guide. And do not attack a hundred-year-old piece with an abrasive, because the soft patina in engraved recesses is part of what makes it look its age, and it does not come back.
Preventing it
Jewelry on last, after cosmetics and perfume; jewelry off first, before swimming, showering and cleaning. Store dry, ideally in a soft pouch rather than a sealed plastic bag, since trapped moisture is worse than air. Wipe pieces with a soft cloth when you take them off, which removes the day's salt before it can do anything. That is the whole regimen, and it is the same one set out in how to store jewelry.
Frequently asked questions
Can real gold tarnish?
Pure gold cannot. The copper, silver and other metals alloyed with it can, which is why lower karat gold darkens and 22K effectively does not.
Why did my 9K gold chain go dark?
Because 9K is 62.5% other metals, mostly copper, and copper oxidises. It is normal, it is reversible with soap and water, and it is not a sign the gold is fake.
Does 18K gold tarnish?
Very little. At 75% gold there is not much reactive metal left, and most dullness on 18K is a film of cosmetics and skin residue rather than tarnish.
Will chlorine damage gold jewelry?
Yes, seriously. Chlorine attacks the alloy metals and can weaken the structure to the point of breakage. Take gold off before swimming.
How do I clean tarnished gold?
Warm water, a drop of dish soap, a soft toothbrush, a good rinse and a thorough dry. Avoid silver dip entirely and avoid ultrasonic cleaners on antique or stone-set pieces.
Why does gold leave a black mark on my skin?
Usually metallic abrasion from cosmetics containing fine particles, which rub tiny amounts of metal off onto the skin, rather than tarnish. It washes off.
Does white gold tarnish?
The alloy does not, but the rhodium plating wears off and the gold beneath looks warmer and duller. That is wear, not tarnish, and replating restores it.
Read next: Can you shower with gold jewelry? · 14K vs 18K gold · Why does jewelry turn your skin green?
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