People Have Many Questions About Jewelry
When silver turns black, does this mean it is cheap? How do you clean it? Can you prevent silver jewelry from turning dark? What coating can be applied to silver, brass, or copper jewelry? Variations of these questions are the most popular. Let’s dive into the answers.
Only sterling silver should be stamped “S925,” “925” or “.925,” meaning 92.5% pure silver. The remaining 0.75% is made up of an alloy consisting mainly of copper which oxidizes over time. Alloying with copper maintains the silvery color while increasing metal strength. (Other metals that may be used in sterling silver include zinc, platinum, and germanium.)
When copper is exposed to oxygen, it darkens and eventually turns green. This reaction, called oxidation, occurs much more rapidly under humid conditions. Sterling silver does not usually turn green but will turn nearly black if not protected with a special coating.
Though stamping is meant to properly identify composition and protect consumers, some unscrupulous competitive manufacturers stamp jewelry plated with 925 silver. Alloy or copper with silver plating, by volume, is not 92.5% silver but initially, they will tarnish in the same manner. The thickness of the plating varies from 1 to 3 microns (0.000039 to 0.00012 inches).
When silver plating eventually wears off, the color of underlying metal shows through, subject to its rate of oxidation. Hence, silver-plated zinc alloy is less distracting than silver-plated copper, for example. People may have allergic reactions to nickel or other metals. The copper within some alloys can turn green and transfer to the skin.
Tarnishing is naturally occurring black sulfide on some metal composites.
Fine silver is 99.9% silver that does not tarnish and is disproportionately more expensive. Argentium silver is a new type of sterling silver that is tarnish-resistant. Only certain chemicals will tarnish Argentium but it does not tarnish from oxidation. White gold (a mixture of pure yellow gold and other white metals) is another tarnish-free precious metal.
Platinum is the most expensive white metal. Some metals that contain little to no silver are branded with names that make them seem like real silver. Nickel silver does not contain any silver at all.
Tibetan silver refers to a variety of white non-precious metal alloys with an appearance similar to aged silver. Stainless steel is an inexpensive and durable tarnish-free metal. It is an alloy that can contain nickel but usually does not for jewelry.
Tarnishing, therefore, is not necessarily a sign of inferior silver quality. Rather, it is naturally occurring black silver sulfide (Ag2S) on some metal composites containing copper or brass. The quality of the metal you choose is dependent upon your budget and the type of jewelry.
A ring—especially a wedding ring—is subject to considerable wear. Watches also get their share of bumps and scrapes. Brooches, pins, earrings, and necklaces, worn occasionally, are more appropriate items for lesser-quality metals and gemstones.
Statistically, 3 percent of the population have skin chemistry that causes Sterling silver to turn their skin green, black, or grey. When silver tarnishes, the jewelry darkens and the oxidation can rub off on the skin, causing discoloration.
How to Remove Tarnish
Tarnish is not permanent. Here is a natural way to remove tarnish:
- Wrap tarnished silver in aluminum foil.
- Put the foil-wrapped tarnished silver in 1 cup of hot water with 2 Tbsp baking soda.
- Chemical reaction will begin to fizzle and bubble for a few minutes.
- Aluminum foil becomes tarnished and silver just needs a light polish.
- Rinse and dry off silver with a soft cloth to remove residual tarnish.
- Pour the used solution down the drain.
- Remove jewelry when showering, swimming, or applying hand sanitizers or sunscreen.
This method may be used on silver, gold, copper, bronze, or brass items. Unlike harsh acids and chemicals, baking soda and water will not harm your skin or gem settings. Since the amount of oxidation is proportionate to air exposure, oils in your skin, and chemicals, it is advised to handle cleaned jewelry with white cotton or nitrile gloves. (Rubber causes a negative chemical reaction reaction with silver.) You can then store jewelry within Ziplock bags with silica desiccant packs.
Without clear protection or electroplating, sterling silver can tarnish again within days of being exposed to air. Inexpensive acrylic spray or varnish can be problematic as they flake, crack, or yellow. Removal of this varnish may damage the underlying surface.
It is possible to minimize or even eliminate periodic tarnish-removal with a sealant. Everbrite is a clear coating that expands and contracts with silver without cracking or yellowing. A thin coat of Everbrite dries to the touch in about an hour but takes 4–5 days to cure completely. It is possible to hasten curing by placing dried items in a 180°F oven for an hour. Clear-coated jewelry increases the perceived value. When coating is performed by the manufacturer or reseller, the extra process may increase the cost of items. The semi-permanent Everbrite coating can be removed, if desired, with xylene or other solvents.
Most people are unwilling to incur the added time and expense of coating personal jewelry. Fortunately, we are progressively coating ClinicalPins that may be prone to discoloration. As this is completed, product pages indicate so.
If Sterling silver jewelry is not coated, the best way to slow tarnishing is to thoroughly wipe pieces with a jewelry polishing cloth after use. Then place them in a moisture-proof air-tight container.
Ways to Test for Precious Metal
How can you tell if an item is precious metal or plated? Of several methods, the most expensive acid test is the most reliable (and potentially damaging to the jewelry):
Rub test is the easiest but not reliable. All it takes is a white cotton cloth. Rub briskly on an inconspicuous area. If black marks appear on it, then the object is sterling silver. This is because 925 silver oxidizes when it is exposed to air. This is not reliable because some sterling silver may be plated with rhodium or have a clear coating to prevent tarnishing. Conversely, lessor metals may be plated with Sterling silver that leaves a mark when rubbed. Real gold or platinum leaves no mark, while counterfeit gold or alloy leaves gold-colored residue on the cloth.
Magnet tests are also easy to perform but not entirely reliable. Silver, gold, and platinum, are non-ferrous materials, meaning that they are not magnetic. If the jewelry is attracted to a magnet, then it is not sterling silver. It may be highly polished stainless steel. Stainless steel does not oxidize but it is not valuable as silver. This test is not foolproof because some non-precious metals like aluminum, copper, lead, tin, titanium, and zinc are not magnetic.
Nitric acid test is the most reliable. Silver-plated or low-quality silver items are likely to turn a greenish color, due to the high level of copper. Depending upon thickness of plating, it may be necessary to scratch the surface in an inconspicuous area with a pin so the nitric acid (HNO3) can react to the metal beneath the coating. (This may devalue coins or investment jewelry.) Real 925 sterling silver jewelry will turn a light cream color.
White Metals Testing Kit Video
In summary, though tarnish is indicative of Sterling silver and tarnish can be removed, most consumers consider discoloration a sign of inferior quality. Good Sterling silver (92.5%) tarnishes unless it is plated with another non-tarnishing metal or has a protective clear coating. Expensive Fine silver (99.9%) and other precious white metals like platinum or white gold will not tarnish. Stainless steel does not tarnish either but it is not a precious metal.
