Why Tarnish and Patina Are Not the Same Thing

Brass and copper both react with the air around them, and both darken as a result. Collectors, though, use two different words for what is chemically a similar process. Tarnish is the dull, greasy, uneven film that makes a piece look neglected. Patina is the deep, warm, even bloom that takes decades to develop, and it can add real value to a copper coal scuttle, a brass carriage clock or a pair of Arts and Crafts candlesticks. The aim of gentle cleaning is to lift the first without destroying the second.

That means setting aside the instinct to make everything look new. A Victorian brass door knocker stripped back to a mirror finish can lose a surprising amount of its value, while a pitted copper bowl with a rich brown surface may be worth more untouched than gleaming. Work slowly, and stop while the metal still has some colour in it.

Know What You Are Cleaning Before You Wet a Cloth

Not every golden-looking object is solid brass. Much twentieth-century brassware, and nearly all modern reproduction pieces, carry a thin lacquer coating. That coating is doing the work for you: a wipe with warm soapy water is the whole job. Polish will cut straight through the lacquer and leave you with patchy, fast-tarnishing metal underneath.

Before you begin, test in an inconspicuous spot such as the underside of a base or the back of a handle. Check whether the piece is magnetic, which usually points to a plated or hollow article. Inspect for a tin lining inside copper cookware, which should never be polished, and for wooden handles, leather washers or old repairs, none of which enjoy a soaking. If a piece is heavily gilded, set with enamel or of serious value, leave it alone and take advice.

The Gentlest Start: Warm Water and Mild Soap

Nine pieces out of ten need nothing more than this. Fill a bowl with warm water, add two or three drops of washing-up liquid, and use a soft cotton cloth or microfibre pad. Work over the surface rather than scrubbing into it. Cotton buds are ideal for engraving, beading and the recesses of cast decoration, where grime collects and where abrasive residues love to hide.

• Wipe rather than dunk. Rinse by wiping with a clean, damp cloth rather than immersing the whole object.
• Dry immediately with a soft, lint-free cloth. Water left in crevices causes spotting and, on copper, fresh green verdigris.
• Keep the water warm, never hot. Heat can loosen soldered joints, shellac-filled repairs and old glue.

Lemon, Salt and Vinegar: Powerful, but on a Short Leash

Acid dissolves tarnish, and the kitchen cupboard will happily supply it. A paste of lemon juice and bicarbonate of soda, or white vinegar with a teaspoon of salt, will shift light oxidation in minutes. The rules matter more than the recipe.

• Apply with a cloth, leave for no more than five minutes, then rinse thoroughly. Never leave an acidic paste on overnight.
• Rinse twice, then dry at once. If your water is hard, finish with a wipe of distilled water to avoid lime spots.
• Skip salt on anything with iron or steel fittings — screws, hinges, handles — because acid attacks them and chloride residues encourage future corrosion.
• Never use these pastes on lacquered brass or on silvered, tinned or gilded surfaces.

Fine Abrasives: Where They Help and Where They Ruin Value

When tarnish has sat long enough to become black and pitted, acid alone will not shift it. Reach for the finest abrasive you can find and use the lightest pressure. A paste of bicarbonate of soda and a little water on a soft cloth, or a jeweller's rouge cloth, will lift stubborn spots. Work in straight lines on flat surfaces — a circular motion shows as swirl marks under a lamp.

Proprietary liquid dips, particularly those containing ammonia, are best avoided. They strip patina in seconds, leave a pinkish bloom on copper and creep into joints where they carry on working long after you have put the bottle away. Steel wool and scouring pads are worse still: fragments embed in the surface and rust, leaving a rash of brown speckles within weeks. Only on heavily corroded pieces of little value should you consider 0000-grade wire wool, used wet with soapy water as a lubricant and worked in one direction only.

Drying, Waxing and Keeping the Shine

Clean brass and copper begin to tarnish again within days in a damp house or anywhere near the coast. Once a piece is dry, warm it very gently with a hairdryer on a cool setting, then apply a thin coat of microcrystalline wax — the standard in museum conservation — or, at a push, a plain beeswax polish. Work it into the details with a soft brush, leave it to haze, then buff with a clean cloth.

Handle finished pieces with cotton gloves, since skin oils are mildly acidic and show up quickly on polished metal. Keep copper away from damp cupboards and never store it in direct contact with newspaper or rubber bands. Reapply wax every six months or so, and dust rather than polish in between. Handled that way, a piece can keep its glow for years and still hold on to the warm, honest colour that made you buy it in the first place.