COPENHAGEN, DENMARK—Tests of ancient Egyptian papyri suggest that metal-filled black ink was used across Egypt from roughly 200 B.C. to A.D. 100, according to a report in Cosmos. It had been thought that most writing had been completed with carbon-based ink until the fourth or fifth century A.D. Thomas Christiansen of the University of Copenhagen and his team analyzed inks from papyri printed before 88 B.C., and a second group of papyri dated up to the second century A.D., with radiation-based X-ray microscopy at the European Synchrotron Radiation Facility. All four varieties of ink identified on the papyri contained copper, in the form of the minerals cuprite, azurite, and malachite. The researchers think soot and charcoal created during the process of removing copper from ores may have been used in the ink. Christiansen notes the blue pigment used by the ancient Egyptians was produced with copper scraps from the metal workshops attached to temples. For more on the use of Egyptian blue, go to “Hidden Blues.”