sepia

Artist's ink made from the brown pigment derived from the ink of cuttlefish, an invertebrate related to the octopus and squid. The cuttlefish uses the natural ink defensively. To make artist's ink, the animal's ink sac is extracted, dried, then dissolved in dilute alkali, and further processed. The resulting pigment is chemically inert and fairly permanent; it is used primarily as a drawing ink and to apply washes. Sepia ink has been used at least since ancient Roman times. It was particularly popular as a drawing medium from the Renaissance onwards, and in the late 18th and 19th centuries generally replaced bistre as a medium for making wash drawings.