Why is my silver jewellery changing colour?

(2023)

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Silver has been used in jewellery, particularly as rings for thousands of years. It does not cause any allergic reactions. Rather it is widely used in surgical equipment for its antimicrobial properties. Silver is soft, like gold, in its pure form. It cannot be used to make jewellery in its pure form. Therefore, the jewellers add copper and other alloys to increase the durability of the jewellery. But these metal alloys are reactive to certain compounds and cause discoloration of the jewellery. Initially, you will notice a dull brown patina over the surface that robes the jewellery of its bright lustre with time. There are many reasons for changing the colour of silver. But, let’s have a look at the few grades of silver that are widely used in jewellery-making before we dive deeply into the topic.

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• Fine .999 Silver

The purest form of silver with 99.9% purity is generally referred to as Fine Silver. It has a vitreous lustre and is tarnish-resistant. The fine silver is soft and unfit for jewellery making. However, it can be used for earrings and necklaces that don’t bounce off frequently.

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• Sterling .925 Silver

This is most widely used in jewellery-making around the world. It is 92.5% pure silver, the rest 7.5% is copper or nickel. That is why it is referred to as “925 Sterling Silver” or just 925 Silver. A slight proportion of copper metal is necessary to harden the silver as in pure form. Otherwise, it cannot be moulded into intricate jewellery designs. They also impart colours to the metal. 

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• Silver Plated

Silver-plated jewellery is copper jewellery lined with a thin coating of pure silver. The thin coating is bound to flake off with time. Like other jewellery, this may happen for many reasons. Wear and tear, exposure to moisture and chemicals, all unveil the metal underneath. And we all know that the metals are reactive and corrosive.

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• Non-Tarnish Alloys or Argentium Silver

The non-tarnish alloys are new in the market. They are composed of silver sterling and germanium. The germanium enhances the hardness and makes them tarnish-resistant in normal conditions for longer periods. The Argentium is, however, rare and expensive than the sterling.

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SILVER JEWELRY IS GETTING TARNISHED

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The corrosion of jewellery is a natural process. This is because the jewellery contains metal alloys to enhance durability and lustre. Precious metals like gold and silver are non-reactive and non-corrosive in their pure form. It belongs to the Noble family. The change of colour is the result of the reactions of alloys. 

This is a common occurrence due to daily use as well as for several other reasons. Chemical products like perfumes, shampoos, cleaning products, corrosive acids (if you work in a lab) may also react with the Silver Sterling. 

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Cosmetic products are another major reason for the tarnishing of silver. The finely powdered products are harder than the metal itself. Metal also reacts with air-borne sulphur particles in form of sulphide or hydrogen sulphide. the pH of the body also affects the jewellery you wear. Acidic pH can boost the blackening of the ring, and ultimately leaving a black smudge on your skin. 

The two important reactions of sterling silver are the reaction of metal alloys as copper and the reaction of sterling silver with sulphur.

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The reaction of Copper in the Sterling Silver

When exposed to moisture or air, the copper in the silver jewellery attains a golden hue. It changes to black with time. Copper is most reactive to acidic substances like bleach, chlorine, ammonia, etc. These compounds give a quick turnaround than moisture. The sweat is also acidic in pH. That means that sweat can also contribute to the tarnishing of the ring or other jewellery. 

 

The reaction of Sterling Silver with Sulphur

Exposure of the silver jewellery to sulphur-containing gases causes it to tarnish.  It discolours and darkens the jewellery. If it is pure silver, the tarnish compound is silver sulphide (Ag2S). In the case of sterling silver, it also forms copper sulphide (Cu2S) because sterling silver has 7.5% copper in composition. The most common sulphur-containing gas is hydrogen sulphide (H2S). The cheapest household source of gas is a hard-boiled egg.  Other sources of the gas include heating fuels, paints, adhesives, etc. 

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STERLING SILVER IS CHANGING COLORS

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The increment of copper in 925silver makes it reactive to oxygen. It also reacts with hydrogen sulfide in the polluted atmosphere, or when cooking food like eggs, onion, or fish. This causes sterling silver to tarnish. The tarnish is initially dull brown. It changes to dark green or black with time. The change of color is associated with the inference of the light. You must be familiar with thin-film inference. As the light hits the tarnish layer, part of it splits and the rest of it reflects off the surface and under the surface. When these lights interfere again, some colors are lost. The color that is displayed depends on the thickness of the tarnish layer. For the thickness of;

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• 10-100 nanometer: Yellow to Red-brown

• >100 nanometers: Black color

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RATE OF COLOR CHANGE

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Even the silver925 is prone to tarnish. This tarnish is not because of the oxidation reaction. It is rather a sulfur induced reaction. The rate of the reaction depends on the sulfur present in the atmosphere. You can perform a simple experiment of exposing silver to a freshly hard-boiled egg. It gives off sulfur dioxide gas. This would make silver tarnish within minutes. Thus, the more the concentration of gas, the more quickly it will tarnish. Moist and humid conditions further aggravate the process. This is a potent issue in hot, humid regions. Therefore it is recommended to store the jewelry below 50% relative humidity.

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HOW TO AVOID COLOR CHANGE IN STERLING SILVER?

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Ok, so we have made peace with the fact that tarnish of sterling silver is unavoidable. Now the question arises what to do to avoid the change of color? How to care for silver jewelry? The answer is simple. 

1. Keep the rings and jewelry clean. Use a silver cloth or particular cleaning solutions.

2. A mild tarnish can be easily cleaned by washing the ring in a warm soapy solution. Rub it gently with your fingers and then pat dry. Or simply dampen a cotton swab to clean the jewelry with gemstones.  Do not wear gloves as they may release sulfides. 

3. When you are dolling-up yourself, put on the jewelry at last. But take it off first after the event. Wearing the jewelry regularly helps prevent tarnish.

4. Use suitable moisture-absorbent on your skin if you sweat liters in summer. 

5. Avoid wearing jewelry in polluted places (hydrogen Sulfide is an environmental pollutant gas).

6. Take off your ring or bracelet of sterling silver before busying yourself in the kitchen with eggs, onions, or vinegar. 

7. Also, take it off when dealing with household cleaning chemicals. These contain chlorine and bleaching agents that can dull the shine. 

8. Store them in a dry or moisture-free box or clean airtight plastic bag after wrapping them in acid-free paper to avoid scratches or abrasion.

9. Prefer the container lined with an anti-tarnish strip or moisture-absorbent compounds. They can potentially slow down the process.

10. Get your rings and jewelry rhodium plated. Rhodium is another noble metal that is non-reactive, non-corrosive, and protective of other metals. 

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HOW TO PREVENT COLOR CHANGE IN SILVER PLATED JEWELRY?

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The tarnishing process is fast in silver plated jewelry compared to sterling silver. The plated jewels have only a thin coating of silver, a size of a few microns. This can wear off because of several reasons and expose the base copper or nickel jewelry to the atmospheric stressors. The resultant oxidation process produces a dark green or black smudge on your skin. This can be avoided by taking care of the jewelry. You can;

1. Coat the inside of your silver plated ring with transparent nail paint. This helps avoid the oxidation reaction and creates a barrier between the ring and your skin. The varnish layer can be replaced easily.

2. You can clean the silver-plated jewelry by submerging it in a warm solution of baking soda and table salt. Rinse it thoroughly and pat dry.

3. You can also employ various other methods to clean off the tarnish and dull color of your silver plated jewelry. These include rinsing with baby shampoo, toothpaste, lemon juice, etc.

4. You can always rhodium plate your jewels. This gives life as well as shine to the jewellery. 

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BOTTOM LINE

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The tarnish or the change of the colour is inevitable with the purest of the sterling silver. But that doesn’t mean that you should not buy or wear the silver jewels. The process is very slow. And it can be easily arrested with proper care and cleansing. Just make sure that the jewellery is not exposed to sulphides or hydrogen sulphide at home, salon, spa, or workplace. Rinse and clean them thoroughly after use and don’t forget to pat dry. It is even better to leave your jewels at home in an airtight box lined with an anti-tarnish strip. If you hold dear your silver sterling, go for a protective coat of rhodium plating. 

(Reference from 'www.thespecialjewels.com')

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