Archaeological fakes may now have a tougher time slipping through, thanks to a novel discovery: Scientists say clay keeps a magnetic timestamp that can distinguish ancient pots from modern knockoffs, reports Smithsonian Magazine. Researchers at UC San Diego's Scripps Institution of Oceanography report in PNAS that fired clay records Earth's magnetic field in two ways: a strong, original signal set when it was heated in a kiln, and a weaker one that slowly builds up over centuries. By reheating 45 samples of both verified ancient and clearly modern pottery, they found a temperature "cutoff" where that weaker, time-dependent signal vanishes.
In their tests, pieces older than about 1,000 years had to be heated to at least 233 degrees Fahrenheit to erase it, but recent objects lost the signal at lower temperatures, per Haaretz. The team says that simple threshold provides a way to flag forged artifacts. "I hope that our new method will be useful for museum curators, who wish to display only authentic artifacts, for archaeologists and historians, studying the societies which created them, and for law enforcement authorities in their effort to eliminate illicit antiquities trade," says study co-author Yoav Vaknin in a statement. Researchers already tested three suspicious items seized by Israel's antiquities authority—and the magnetic signatures suggest all three really were fired in antiquity.
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