Reading patina

What surface color tells you — and doesn’t.

Patina is the layer that forms on metal over time, and each metal writes its own. Copper alloys range from smooth mid-brown through olive to green and blue corrosion products sitting in the recesses. Silver tarnishes grey-black, lead goes a dull white-grey, and iron swells into orange-brown rust.

A stable, even patina that follows the object’s form is a good sign of age. Bright, powdery, or patchy green on a copper alloy can indicate active corrosion that needs conservation — keep the object dry and isolated until it settles.

Beware a painted-on “antique” finish: real patina sits in the low points and wears from the high points, never the reverse. A patina that scratches off to bright metal with a fingernail, or smells of chemicals, was applied last month, not last millennium.

Never strip patina to “clean up” a find. The surface is part of the object’s history, often carries the finest detail, and once removed it cannot be put back. Record the colours you see and where they sit.

From the guide library inside Collectors Catalogues, a free app for cataloguing antiques and finds with honest, museum-grade records.

More on skills

Spotting casting seams — How an object was made narrows its date.

Recognising modern copies — The tells of a later reproduction.

General signs of a reproduction — What later copies get wrong.

Reading hallmarks and maker marks — A punched paper trail.

Weighing and the density test — Mass tells on fakes.

Using UV and magnification — Seeing what the eye misses.

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