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**Roman-era ink reveals surprising chemical complexity**
"_University of Évora archaeologist César Oliveira, the lead author of the new study, says the ink’s basic ingredients were as expected, but ‘the surprising element is the intentional inclusion of iron-gall ink constituents, creating a hybrid of carbon-based and metal-based ingredients’. The tannin from oak galls combined with iron salts during the ink-making process to create an intense black or dark purple ink._"
