The meaning of the word ‘Tarnish’
Tarnish is a thin layer of corrosion that forms on the outermost layer of a metal as it undergoes a chemical reaction. It does not always result from the effect of oxygen in the air. It often appears as a dull, grey surface over the metal. Only the top few layers of the metal react, and the layer of tarnish seals and protects the underlying layers from reacting. For this reason, tarnishing is never harmful. However, some of the aesthetic appeal from the original finish may result. The term patina sometimes applies to Antique jewellery. For example, Platinum. This protective layer formed over many years adds to the authenticity of some Vintage and Estate jewellery.
Are precious metals subject to tarnishing?
Most precious metals tarnish over a long period of time. There are, however, suitable precious metals more resistant to tarnishing in the shorter term. For example, Platinum, Palladium and 18ct Gold.
Rhodium and the popular misbelief of tarnishing
For anyone purchasing 9 carat or 18 carat White Gold, their item of jewellery will include a blistering white plating of Rhodium. This hard electroplated metal gives protection and improves the whiteness of the finished item. Owing to the natural off-white colour of most White Gold, Rhodium remains a standard final process. Over time, Rhodium wears. For example, on the underside of a ring shank. As a result, many buyers identify this as tarnish. Instead, the true colour of the metal reveals itself after wear. We provided some examples of Rhodium and the process of coating, dipping or plating rings in our previous post.
What is the most common metal to tarnish?
From my experience, the most common metal to tarnish is Silver. For this reason, some Silver jewellery undergoes Rhodium plating. Rhodium is less reactive in air. As a result, items of Silver jewellery Rhodium plated in the end stage, react less. The upkeep of Silver jewellery under spotlights and in jewellery windows involves regular cleaning to ensure the bright finish.
What about Platinum, Palladium and Gold? Do they tarnish?
9 carat Gold tarnishes more easily than 18ct Gold. Owing to the higher amount of impurities (such as Copper) 9 carat Gold reacts more in the air. For this reason, we recommend 18ct Gold for durability and resistance to tarnishing. Platinum and Palladium are 95% pure. In addition, they are far less reactive than most metals. As a result, Platinum and Palladium are tarnish resistant. They are uncoated. Their metal colour is the natural surface of the metal. Finally, Platinum and Palladium easily re-polish back to their as-new condition. Please remember that scratching as nothing to do with tarnishing. Platinum will scratch as will Palladium scratch over time. This is natural. Re-polishing restores the new appearance and mirror finish. This is a service offered by most jewellers.