Uncovering The Formula For a Mysterious, Medieval Blue Ink

For thousands and thousands of years a purple-blue ink known as folium was used to color all kinds of books, cheese rinds and more, but its formula was lost until a team of researchers recently deciphered the recipe through three ancient texts. It’s long been confirmed that the dye comes from the fruit of chrozophora tinctoria, but this isn’t a complete assessment. By poring over the manuscripts (one from the 12th century, another from the 14th century and a 15th-century manual literally called The Book on How to Make All the Colour Paints for Illuminating Books), scientists found that the fruit needs to be carefully soaked in a mixture of methanol and water, before further steps are taken. Maria João Melo (a scientist and co-author of the study) says “They were able to produce paints that last centuries. We don’t have such paints now. So this is part of our research—to know as much as possible about this material that was completely lost with the advent of the synthetic dyes.” Find out more at Atlas Obscura.