Spotting casting seams

How an object was made narrows its date.

A faint raised line running around the outer edge is a casting seam, left where two halves of a mold met. Filing marks nearby show it was cleaned up by hand. Look also for the stub or scar of a sprue — the channel the metal was poured through — often hidden on a base or edge.

Not every genuine cast has a seam: lost-wax casting, standard for much ancient metalwork, uses a one-piece mold destroyed at each casting and leaves none. A seam on an object type usually made by lost-wax deserves a closer look.

Machine-made reproductions tend to have crisp, regular seams and no hand-finishing. Ancient and medieval casts show irregular, softened tool marks from files and burnishers that themselves differ from modern rotary-tool traces.

Look at the back, the underside, and inside hollow forms — that is where finishing was skipped and the truth shows. Record what you find there as carefully as the display face.

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

More on skills

Reading patina — What surface color tells you — and doesn’t.

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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