Lost Recipe for Medieval Blue Ink Found

The plant used to create a popular blueish-purple ink once used in illuminated manuscripts--and the ink's recipe--has eluded scientists… until now.

The pigment known in the Middle Ages as folium was famous for its gorgeous blue/purple color and its staying power. Although it, along with the more well-known blue indigo pigment, was used to dye textiles, it was mostly used by monks to illuminate manuscripts.

Upon the advent of the printing press, over time the process for producing this color was lost… until a group of chemists, scientists, and biologists at the New University of Lisbon, Portugal, found the recipe in a 15th-century manuscript written in the extinct Judeo-Portugese language of Lusitanic.

Although the translation proved difficult, the team was able to translate enough of the recipe to identify the dye’s sole ingredient: Chrozophora tinctoria, a plant native to the Middle East, India, Pakistan, and Central Asia. In the summer, the plant produces a fruit approximately the size of a walnut that contains a blue fluid, which then turns into a small nut in the fall.

The group scoured the neighboring countryside for the plant and found them in the Portuguese town of Monsaraz, where the locals considered the plant a weed. After some experimentation, they ultimately followed the book’s instructions on how to collect the fruit in July and then squeeze out the fluid onto linen, being careful to not break the seeds. From this substance they were able to re-create the medieval dye, which they believe is so stable that it may retain its original color for centuries.

The discovery they hope will help manuscript conservationists repair areas with the original pigment, rather than modern, synthetic ones. The team has named their new pigment Chrozophoridin.