Smithsonian Magazine · Geschiedenis en cultuur

Earth's Magnetic Field Can Reveal Fake Ancient Pottery

Researchers have developed a new method to authenticate ancient pottery by analyzing its magnetic signatures, potentially aiding museums, archaeologists, and law enforcement in identifying forgeries and combating the illicit antiquities trade.

A team at the Scripps Institution of Oceanography at the University of California, San Diego, has detailed a new technique in the Proceedings of the National Academy of Sciences that could help identify falsified archaeological artifacts globally.

The method relies on the magnetic field imprinted in clay when it's fired. Clay objects contain ferromagnetic minerals, and as they cool in a kiln, their magnetic field aligns with Earth's magnetic North Pole, creating a thermal remanent magnetization (TRM). Because the pole's location shifts, ancient pottery's TRM points differently than modern pottery.

Over centuries, clay also acquires a weaker, secondary magnetic signal called viscous remanent magnetization (VRM), which records different magnetic field intensities and directions. While VRM has been known for over a century, it was often dismissed as 'noise' obscuring the TRM.

The researchers tested 45 pottery samples, including ancient shards, royal Judean jars, modern vessels, and souvenir pottery. They heated these samples incrementally to determine at what temperature the VRM signals disappear, leaving only the TRMs. They found that samples older than a millennium required heating to at least 234 degrees Fahrenheit to erase their VRM, while newer pottery's VRM could be erased at lower temperatures.

This discovered temperature threshold could assist in detecting artifact forgery, which is prevalent in archaeologically rich countries. The researchers also successfully applied the method to three confiscated artifacts of questionable authenticity, suggesting they were fired in ancient times, highlighting the method's utility in identifying looted and illegally traded real artifacts.

The researchers acknowledge a challenge in authentication: forgers can potentially read scientific papers and adapt their methods to deceive detection techniques.

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