Metal Identification: A Guide to Cast Antique Metalware


Please respect your collectibles, and use only non-destructive methods of identification.

1. Does a magnet stick?

Yes: Iron or steel. A magnet has a place in every collector's tool kit.
No: Go to 2.

2. What color is the bare metal? If plated or patinated, look on the bottom, or at worn spots. Please do not scratch the metal. 

Gray: Zinc.
Yellow, golden: Brass or Bronze, go to 3.
If color can not be determined: go to 3.

3. Tap the piece lightly with a pencil, and listen carefully. For best results, tap a sculpture on the end of an arm. For a plaque, hold by a corner, and tap the opposite corner. 

Thud: Zinc
Faint dull ringing: Brass
Clear ringing tone: Bronze

Metal Facts & Fiction:

Zinc: Also known as pot metal, spelter, white metal, and even "french bronze". Soft, does not take detail well. Brittle, not malleable; breaks if bent. Easy to cast. Cast zinc pieces are usually hollow. Weighs 4.16 ounces per cubic inch.

Brass: An alloy of copper and zinc, usually 50% copper, 50% zinc. Somewhat malleable; bends some without breaking. Intermediate hardness, takes detail moderately well. Moderately easy to cast. Weighs 4.94 ounces per cubic inch.

Bronze: An alloy of copper and tin. Without any applied patina, it is the same color as some brass. Hard, takes detail very well. Brittle, not malleable; breaks if bent. Difficult to cast. Weighs 4.71 ounces per cubic inch. Lesser grades of bronze can also have some zinc in the alloy, resulting in properties closer to brass.

Fiction:

It's very heavy, it must be bronze. False. The specific gravities (ounces per cubic inch) of these metals are too close to distinguish by heft.

Its color identifies it as bronze. False. Without an applied patina, bronze is the same color as some brass.

It's bronze because it's a "Vienna" or "Austrian" bronze. False. Most Vienna-Austrian Bronzes are actually yellow brass. The Technical Research Institute in Vienna reported in 1991 that the Bermann company has been using only yellow brass since 1850.

It's bronze because it's marked "Armor Bronze", "Pompeian Bronze", or "Marion Bronze". False. These pieces are zinc with a copper coating, produced by the "Electroformed" or "Galvano" process.

It's copper. Not if it's cast. Most likely, it's zinc or cast iron with a copper plating.

It's pewter. Not if it's antique cast sculpture, bookends, etc.. Most likely, it's zinc.

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