What is the difference between tarnish, oxidation and plating wear?

ZKZ Editorial TeamMain answer · Product & gemmology desk

Tarnish is a dark surface layer that forms on silver when it reacts with gases and other substances in the air, and it can be cleaned off. "Oxidised" can mean a deliberate dark finish on a design, or a loose word for tarnish. Plating wear is the thin surface coating, such as rhodium, rubbing away so that the metal beneath shows. The fix differs, so identify the problem first.

Tarnish

Fact One maker of anti-tarnish products says the gases that cause tarnish are atmospheric pollutants including sulfur gases, chlorine, ozone and nitrous gases, and that its products prevent tarnish from forming but will not remove tarnish that has already started. GIA says chemicals can discolour precious metals including silver.

Our advice Tarnish looks yellow, brown, grey or black, and it often collects in recesses. It tends to appear gradually on plain, unplated silver, and faster in humid air or with some products. It can usually be cleaned off with a polishing cloth or by a jeweler.

Oxidised finish

Our advice Some silver jewelry is deliberately darkened in the recesses to bring out the design, and this is sold as "oxidised" silver. It is a finish chosen by the maker. If you polish it hard, you remove the dark areas.

Uncertain In strict chemistry, "oxidation" covers many reactions, and silver tarnish is mainly a reaction with sulfur compounds rather than with oxygen. In jewelry talk the words are often mixed up, so ask the seller what they mean.

Plating wear

Fact Sellers of rhodium-plated jewelry describe the plating as an extremely thin layer, around 0.5 to 2.5 microns according to one retailer, that wears off over time and needs upkeep. The retailer says that as it fades, the colour underneath can show through.

Fact The FTC Jewelry Guides say it is unfair or deceptive to fail to disclose a surface-layer application of rhodium on products marked or described as precious metal (16 CFR 23.7).

Our advice Plating wear looks like a patch of a different colour, often yellowish or darker, where the piece rubs most, such as the inside of a ring or the edges. Polishing does not fix it. Replating by a jeweler does.

How to tell them apart

1. Where is it? Tarnish can appear anywhere, with a darker look in recesses. Plating wear appears in high-contact areas.
2. What colour? Tarnish is dark. Worn rhodium over silver may show a warmer silver or yellowish tone beneath.
3. Does a cloth help? If a cloth brightens it, it was tarnish. If it does not change, it may be worn plating or a deliberate finish.
4. Ask the seller what the finish is.

What to do

• Tarnish: wipe, polish gently, and store with an anti-tarnish strip.
• Oxidised finish: do not polish heavily. Clean gently.
• Plating wear: ask the seller or a jeweler about replating.

It depends Some people like a worn, lived-in look, and others prefer to keep a bright finish. Neither is wrong.

Related reading: Does 925 Sterling Silver Tarnish? Causes and Fixes · Rhodium Plating on Silver Jewelry: What It Does and How Long It Lasts

Sources

• Intercept Technology, anti-tarnish products FAQ (manufacturer)
• GIA, Tips on caring for jewelry
• J.M. Scully Jewelers, Rhodium plating: does it tarnish, cost, lifespan and care
• Shane Co., About rhodium-plated jewelry
• 16 CFR 23.7, FTC Jewelry Guides: disclosure of surface-layer application of rhodium

Fact = stated by the cited source. Our advice = editorial recommendation. Uncertain / it depends = limits of what can be said in general.