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About the Store | Jewelry & Gemstones
Why does jewelry turn skin black?
18 Carat gold jewelry is best. This discoloration only happens with lower grade alloys such as 9 carat, 10 karat, 14 carat, 14 karat, and possibly 18 karat.
18 Carat contains 75% gold, however American 18 Karat can legally be only 17½ carat, and therefore contains only 72.9% gold. It may not seem to be a large difference, but if you were to study a graph of the properties in gold alloys you would find that at about 75% gold the alloy becomes practically inert to attack and corrosion by most chemicals. 18 Karat is just shy of the standard, where 18 Carat is above the critical level.
The base metal content, mainly copper, in low carat gold alloys can and does get attached by acids in perspiration and in the atmosphere. The result is oxides and other salts which rub off onto the skin and fabrics, leaving black or green marks. The lower the gold content of the alloy equals the higher the proportion of base metal, which is more likely the alloy is to be attacked by acids and other chemicals. Conversely, the higher the carat quality and the lower the base metal content, the less likely there will be any reaction with chemicals.
The solution is simple. Stick to high carat gold alloys such as 18 carat.
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