Multispectral imaging techniques have unearthed an invisible inscription on the back of a pottery shard that has been on display at The Israel Museum for over half a century. Inscription found on reverse of ostracon found at Arad in 1965. Courtesy of the American Friends of Tel Aviv University (AFTAU). The ostracon — ink-inscribed pottery shard — dates back to ca. 600 BCE. The inscription on the front of the shard has been studied by archaeologists and biblical scholars alike, but the back of the pottery was thought to be blank. Researchers at Tel Aviv University (TAU) made the discovery after noticing several faint marks on the back of the ostracon. Using multispectral imaging to acquire a set of images, they were able to decipher 50 characters — 17 words. "The content of the reverse side implies it is a continuation of the text on the front side," said Shira Faigenbaum-Golovin of TAU's Department of Applied Mathematics. "The new inscription begins with a request for wine, as well as a guarantee for assistance if the addressee has any requests of his own," said Arie Shaus of TAU's Department of Applied Mathematics. "It concludes with a request for the provision of a certain commodity to an unnamed person, and a note regarding a 'bath,' an ancient measurement of wine carried by a man named Ge'alyahu." The discovery of the message stresses the importance of multispectral imaging in documenting history. "It's daunting to think how many inscriptions, invisible to the naked eye, have been disposed of during excavations," said Faigenbaum-Golovin. The TAU research has been published in the journal PLOS ONE (doi.org/10.1371/journal.pone.0178400).