银饰发黑怎么办？在家安全清洗银饰的方法

Silver rings and chains that turn yellow and then black over time are perfectly normal; it does not mean the silver is poor quality. Most pieces can be brightened at home once you know how to clean tarnished silver the right way for each type of jewelry. This guide draws on the Canadian Conservation Institute (CCI), the Gemological Institute of America (GIA) and chemistry teaching material from the University of California, Davis.

Why does silver tarnish?

According to the CCI, tarnish on pure silver is silver sulfide, formed when silver reacts with sulfur-containing gases in the air, most commonly hydrogen sulfide. Sterling silver contains copper, so copper sulfide forms as well. Thin tarnish shows yellow, red-brown and blue colours; thicker layers look black. CCI

Sulfur sources are everywhere: rubber (rubber bands, rubber gloves, erasers), wool and wool felt, some foods such as eggs, and certain paints and glues. Silver tarnishes faster as humidity rises; the CCI recommends storing it dry, below 50% relative humidity.

Identify your piece before you clean tarnished silver

• Plain solid or sterling silver without stones: suits most methods in this article.
• Silver-plated pieces: the silver is only a thin outer layer. The CCI warns that for plated silver, any method of tarnish removal may be very damaging. Wash gently and wipe with a soft cloth. CCI Note 9/7
• Oxidized or antiqued silver: the dark recesses are usually a deliberate tarnish layer that highlights the design, and tarnish removal will strip it. GIA recommends gentle solutions or warm soapy water for oxidized or antique metals. GIA
• Pieces with pearls or porous gems: pearls should never go in an ultrasonic or steam cleaner and are damaged by chemicals and acids. GIA Porous gems such as coral and turquoise should also be kept away from chemicals.
• Pieces with sealed hollow parts: the CCI advises against immersing them.

A 4-step routine to clean and brighten silver at home

For solid silver jewelry, this gentle routine handles most light to moderate tarnish:

1. Soak in warm soapy water for a few minutes to loosen dust, skin oil and cosmetic residue. The CCI considers washing with a mild detergent safe for most silver objects.
2. Clean crevices in an ultrasonic cleaner: run a short cycle to shake dirt out of the backs, prongs and chain links. Skip this step for pieces with pearls or stones that cannot take ultrasound.
3. Buff with a silver polishing cloth: the CCI rates polishing cloths as suitable for light tarnish, and GIA suggests a silver cloth for pieces with porous gems or plating. GIA
4. Store in a sealed bag: dry thoroughly, place in a zip-lock bag and press out the air.

Note: polishes are abrasive and remove a very thin layer of silver along with the tarnish, so do not polish too often.

Does the baking soda and aluminum foil method work?

Yes, for heavily tarnished solid silver. It is an electrochemical reaction: when silver touches aluminum in hot water, the aluminum is oxidized (loses electrons) and the silver sulfide is reduced back to metallic silver. A small current flows between the two metals, so the silver must touch the foil. Baking soda reacts with hydrogen sulfide and speeds things up; without it the reaction still works, only more slowly. UC Davis – LibreTexts

Unlike polishing, this converts tarnish back into silver instead of abrading it away. The CCI describes a similar method using a warm washing soda (sodium carbonate) solution.

• Line a heat-proof bowl with foil and place the jewelry so it touches the foil.
• Sprinkle in some baking soda and pour in hot water to cover the jewelry, taking care not to scald yourself.
• Wait until the silver brightens, lift it out, rinse in clean water and dry thoroughly.

The surface is often slightly matte afterwards and needs a light buff with a silver cloth. The CCI also notes that silver treated this way may tarnish again faster. Do not use this method on plated or antiqued silver, or on pieces with stones, pearls or hollow parts.

Will an ultrasonic cleaner remove silver tarnish?

No. Ultrasonic vibration dislodges dust, skin oil and loose residue in crevices that cloths and brushes cannot reach; GIA mentions this advantage for cleaning under stones. Tarnish, however, is silver sulfide bonded to the metal surface. Water and vibration cannot turn it back into silver, so you still need a silver cloth or the electrochemical method.

When using an ultrasonic cleaner on jewelry, GIA advises:

• Do not clean ultrasonically: pearls, coral, amber, gems filled with oil or resin (common in emerald), opal, turquoise, moonstone, tanzanite.
• Check that stones are secure before and after cleaning, because vibration can loosen them.
• If you are unsure about a gem, take it to a jeweler.

How to store silver so it tarnishes less

• Wrap each piece in acid-free tissue and seal it in a polyethylene bag, as the CCI suggests.
• Add silica gel and activated charcoal to the box to keep it dry and absorb tarnishing gases.
• Keep silver away from rubber bands, rubber items, wool and felt.
• Put jewelry on after perfume, hairspray and make-up, especially pieces with pearls, and wipe it gently after wearing.
• Do not polish constantly: the CCI notes a thin tarnish layer helps protect silver, while freshly polished silver tarnishes faster.

Inmax cleaners for homes and jewelry shops

In the Inmax ultrasonic cleaner range, two models suit the crevice-cleaning step:

• U27: 48 kHz ultrasound combined with a 270–280 nm UVC lamp, 200 ml tank, countdown display, 22 W.
• U13: 48 kHz ultrasound, cylindrical 108 mm body, silver-plated lid, 298 g, 20 W, 3, 5 or 10-minute timer.

See how to choose one in our article on mini ultrasonic cleaners for the home. Jewelry and accessory shops that want to stock ultrasonic cleaners can read our dealer policy or compare specifications.

Frequently asked questions

Can you use toothpaste to polish silver?

Better not. GIA lists toothpaste among abrasives that can erode metal and scratch gems.

Does tarnish mean the silver is fake?

Not necessarily. Tarnish is silver's natural reaction with sulfur. Still, tarnish alone cannot tell real from fake; have a reputable jeweler test the piece.

How often should you brighten silver?

Only when needed. Washing with mild soap and drying can be done often; polishing removes a thin layer of silver, so keep it to a minimum.

Can bleach clean silver?

Avoid it. GIA advises against chlorine and bleaching agents, which can damage some gems and metal alloys.

For valuable pieces, antiques or jewelry set with gems that may have been treated, ask a jeweler to assess them before cleaning them yourself.