How to Tell If an Item Is Made of Real Copper
Copper, with its rich caramel hue, adds a charming warmth to your home. And as any collector knows, cleaning and polishing your copper pieces on a regular basis keeps them from looking dull and tarnished. Copper's value derives from its beautiful reddish-gold shade, its strength and corrosion resistance, and its malleability into other shapes. You can find copper in household fixtures, the pipes of your building, in jewelry and even artwork.
But copper's benefits go beyond the aesthetic: The chemical element and metal contains antibacterial properties that make it ideal for preventing the growth of certain fungi and bacteria like E. Coli, MRSA, and legionella. Copper can also bond with other metals. It's also conductive, which is why it is used in electrical wiring. With its plethora of uses, you will want to be sure that your item is the real deal. What are some of the things you should look for when examining a piece for copper while perusing an estate sale, the flea market, or yard sales on Saturday morning?
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The Color Test
Copper and brass are easily confused as they look so similar, but it's their color that distinguishes them. Copper has distinct red and pink tones. Brass, on the other hand, appears more yellow and tends to be much brighter. Look closely subtlety of tones in the item to see whether it is really copper or something else. You may need to polish the item first, especially if it appears dull.
The Magnet Test
Like silver and gold, real copper does not have much magnetism. You can take a magnet and hold it up against the antique piece. Is the magnet drawn to it? Then it is not real copper. Even if an item is made from metal plated with real copper won't pass this test—the metal underneath will draw the magnet. An item that's made entirely of copper, on the other hand, will not attract the magnet. The only exception is a strong magnet, which might be affected by currents generated from the magnet as it moves over the surface of the copper object.
The Oxidation Test
Copper corrodes in a very unique way. It does not rust. Instead, the oxidation process creates a crust that is blue or green in color. Pale-green spots are also an indication that the oxidation is occurring on authentic copper material. If the item has red rust, it is made of an entirely different metal and is not real copper.
Conducive to Electricity
You'll want to be careful when testing this, but real copper is a great conductor of electrical current. To test the authenticity of your copper piece in this way, you will need a device called an ohmmeter that can measure the object's electrical resistance. You'll have to do some math next: take the reading from the ohmmeter and multiply by the cross-sectional area of the item, then divide that number by the length of the object. Real copper will have a resistivity of 1.7 x 10^-8 ohm-meters.
The Density Test
Another test that involves math is the density test. Real copper is fairly dense, measuring at 8.96 g/cm3. Weigh the object, then divide by the object's volume to figure out its density. Is the density the same or very close to the density of copper? Then the object is made of copper. If the number is very different, the object might contain some copper, but is not pure copper.
