Tarnish
Unlike a stain, tarnish is made of the very surface it sits on. Removing it always removes metal.
Precautions
- Test on an inconspicuous area first
In detail
Tarnish is not a deposit. It is the outer layer of the metal itself in a reacted state, formed where copper, brass, bronze or silver meets air, moisture, sulphur compounds and the salts left by handling. That distinction decides everything about treating it: a stain sits on a surface and can be lifted off, whereas tarnish is the surface, so every method that removes it removes metal. Polishes work by combining a mild abrasive with a chemically active medium, cutting and reducing the layer at once, and they are effective — the cost is cumulative and falls first on the shallowest detail, which is why repeatedly polished cast or engraved work loses its crispness. The federal conservation procedure treats this as the governing fact and advises that copper alloy objects should usually not be polished at all, and that where it is necessary the least abrasive approach is used. It also separates tarnish from damage: damage to the metal, including its patina, cannot be addressed by cleaning, so a corrosion pit or a scratch will not respond to more polishing. On a domestic object none of this forbids a shine. It reframes it as a choice with a price rather than as maintenance.
What works
Mild abrasion is effective against Tarnish Supported
An abrasive polish genuinely removes tarnish, and that is precisely why it is dangerous on a plated surface.
Mild cream cleanser is effective against Tarnish Supported
A silver polishing cream is a cream cleanser by another name, and the museum guidance names creams among the products that remove tarnish quickly.
Metal polish is effective against Tarnish Supported
Why
- Tarnish is explained by Coating thickness
Aftercare and prevention
- Metal polish helps prevent Tarnish
Hacks and claims involving this
- Polishing brass and copper back to a shine Disputed
- Aluminium foil and bicarbonate of soda to clean silver Disputed
- Lemon and salt to clean copper Established practitioner practice
When the obvious answer is wrong
How do I get tarnish off silver-plated cutlery without wearing the plating through?
That sentence is also the problem. Tarnish CONTAINS silver, so removing it always removes a little metal, and abrasive polishes carry corrosive acids as well as abrasive compounds. On solid silver that is a slow recurring cost. On plate the silver is only microns thick, so the same treatment is a countdown - and the museum sheet records how it ends: over-polishing plated silver removes the plating and exposes dull base metal that CAN BE MISTAKEN FOR TARNISH. The reader then polishes harder, on the one area with nothing left.
A different kind of treatment works: Work out which you have first, because the answer diverges and hallmarks are how you tell. On plate, drop down the escalation rather than up it. Both conservation bodies direct a silver cleaning CLOTH as the routine treatment for light tarnish on plain undecorated pieces, and the museum sheet states that a cloth or a dip removes far less surface than a polishing cream does. For heavier tarnish the UK professional body permits a silver DIP, with conditions that are not optional: follow the container instructions, wear gloves, use fresh solution, and rinse thoroughly - dip left in crevices keeps corroding and produces a green crust. Electrochemical cleaners, including the aluminium-foil-and-bicarbonate method, are ruled out by both bodies as a class. The larger answer is to clean less.
Sources for this page
Sources
Technical Procedures: Cleaning of Copper Alloy Objects
United States General Services Administration (GSA), Historic Preservation · Reference work
Relied on for: That copper alloy objects should usually not be polished, that the least abrasive approach is used where it is necessary, that commercial cleaners and metal tools are excluded, and that damage including to the patina cannot be addressed by cleaning. (states this directly)