What's wrong? According to Jewelers of America, Inc. Known as "black dermographism," which literally means "black writing on the skin," this phenomenon occurs when the cosmetics contain chemical compounds harder than the jewelry metals they contact. Zinc oxide is a major white pigment used in face powder, creams and lipstick. It has recently been replaced by titanium dioxide, which can be equally hard on jewelry. Rouge and face powders often contain ferric oxide pigments.
And calamine, a tinted oxide, is found in some medicated cosmetics and lotions. They abrade the softer jewelry metals - gold, silver, platinum and nickel - and leave deposits on the skin. These deposits look black because the particles are too small to reflect light. You can remove them with soap and water.
Some people have sulphur in their perspiration that produces a greenish-black stain when it contacts any metal jewelry. Such people should remove rings often and use an absorbent powder on their fingers that's free of zinc oxide. Also, soap, detergent, wax, polish or cosmetic cream can build up under a ring, causing a type of dermatitis.
A burning sensation and redness of the skin results. To prevent this, simply remove rings before using soap or detergent and clean the rings frequently. Certain rings, especially those containing copper and silver alloys, will leave a black smudge on the skin if enough salt is present. Simply exposing the hands to salted nuts, crackers or popcorn can cause such corrosion and thus discolor skin.
The issue is, therefore, not with the gold but with the other metals present on the gold. These are what get affected by environmental, chemical, and biological aspects. The other aspect is if you live by the sea or the ocean. There is salt or chlorine in the air, and when that comes into contact with your skin and after the ring, corrosion begins to take place. That happens when the chemicals in the detergents react with the metal alloy, and as a result, you end up having the black deposit on your hand.
The compounds in the makeup rub finely against the metal and cause corrosion to take place. When metal is rubbed into fine pieces, it becomes black and not the metallic color that you would expect. The sweat on our skin is acidic, and when paired with the alloys on the gold ring, they are bound to cause a reaction and thus tarnish. There is also the factor of hormonal changes that can cause the ring to react and leave the unsightly mark.
There are some ways that you can enjoy wearing your gold ring without having to worry about a black mark forming underneath. If you bought a gold ring for way cheaper than the market value, then it is likely that you have a gold plated ring and not the real deal.
Have you ever had a gold ring that after wearing it for a while, your finger turned black or green? Did you think the reason was bad manufacturing or under karating? This is caused by makeup, or other cosmetics, on the skin.
Cosmetics contain compounds that are harder than the gold remember gold is soft. So the makeup will rub off very tiny particles of the metal. Very small particles of metal appear black in color rather than metallic, so it looks like black dust. When this dust comes in contact with surfaces that are absorbent, such as your skin or clothing, this dust sticks and forms a black smudge.
Another reason that that your finger may discolor is corrosion of the metals in your ring. The gold does not corrode, but the alloys that are mixed with the gold. The alloys that can corrode are silver and copper based, and they can form dark chemical compounds under moist conditions. When you sweat, fats and fatty acids are released which can cause corrosion on your gold ring. This problem is worse in semi tropical locations like when you go on vacation to Hawaii and near the ocean where salt is in the air.
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