How do I clean brass, copper and pewter?

Metal cleaning goes wrong when the method is chosen before the metal is identified. Half of what looks like solid brass is plated, and plating comes off.

Safety

What you'll need

• A magnet
• Lemon, salt, white vinegar and plain flour
• Soft cloths and an old toothbrush

Step by step

1. Test it with a magnet.Brass, copper and pewter are not magnetic. If a magnet sticks, you have plated steel — the surface is a thin coating and any abrasive method will wear straight through it.
2. Check whether it is lacquered.Much modern brass has a clear lacquer over it. If the surface is bright in places and dull or patchy in others, the lacquer is failing. Polish will not touch it — the lacquer has to come off first.
3. Decide whether you want it cleaned at all.Patina on antique brass, copper and pewter is often the greater part of its value, and removing it is irreversible. If the piece might be worth something, ask before you start.
4. Wash it first.Warm soapy water and a soft brush. Grease and dust ground into a polish just makes a fine abrasive slurry, which scratches.
5. Use lemon and salt on brass and copper.Half a lemon dipped in salt, rubbed over the surface. The mild acid dissolves the tarnish and the salt gives just enough abrasion. It works quickly and costs nothing.
6. Use vinegar, salt and flour for a paste.Equal parts white vinegar and flour with a spoonful of salt makes a paste that stays put on vertical surfaces. Leave it thirty minutes, then rinse and buff.
7. Rinse thoroughly and dry immediately.This is the step people skip. Acid left on the surface keeps working and causes patchy discolouration, and water left on copper produces new tarnish within hours.
8. Treat pewter completely differently.Pewter is soft and its soft grey sheen is the point. Warm soapy water and a soft cloth only. Abrasive polish scratches it permanently and a bright shine looks wrong on it.
9. Never put pewter in a dishwasher.The heat and detergent dull and pit it, and pewter with a low melting point can distort. Hand wash in warm, not hot, water.
10. Use proprietary polish for heavy tarnish.A long-tarnished piece may need a commercial brass or copper polish. Apply sparingly with a soft cloth, work in small sections, and buff off completely.
11. Get into detail with a soft brush.An old toothbrush for mouldings and engraving. Polish left dried in the recesses sets white and is worse than the tarnish was.
12. Handle silver as its own case.Silver tarnishes black through sulphur rather than oxidation. The aluminium foil, bicarbonate and hot water method reverses it chemically without abrasion, and is far kinder than polishing.
13. Strip failing lacquer before repolishing.Acetone or a proprietary lacquer remover, then clean the bare metal. Polishing over a patchy lacquer only makes the patchiness more obvious.
14. Protect it afterwards if you want it to last.A thin coat of microcrystalline wax, or renewing the lacquer. Bare brass and copper start tarnishing again immediately, faster in a kitchen or bathroom.
15. Wear gloves for handling afterwards.Fingerprints in the oils on your skin etch freshly cleaned brass and copper within days. Cotton gloves for the final buff and positioning.

Tips

• Magnet test first. If it sticks, it is plated and abrasive cleaning will go through the plating.
• Rinse and dry immediately. Acid left on the surface causes patchy discolouration.
• Pewter is never polished bright. Warm soapy water and nothing more.

Common mistakes

• Polishing plated items — The plating is only microns thick. Abrasive polish takes it off, exposing the base metal underneath, and it cannot be put back without replating.
• Stripping the patina from an antique — On old brass, copper and pewter the patina is usually the larger part of the value. It is irreversible, and a brightly polished antique is generally worth substantially less.

If it doesn't work

Questions people ask