Recent test of Egyptian papyrus shows black ink filled with copper.
According to Cosmos report, this metal-filled ink was used in Egypt from 200 BC to 100 AD. This is 400 years earlier than previously known.
Thomas Christiansen of the University of Copenhagen and his team of scientists used X-ray microscopy at the European Synchrotron Radiation Facility. They scanned papyrus from 88 BC and 200 AD.
They believe the charcoal used to make these inks contained traces of copper left over from the process of separating copper from other ores. Specifically, the copper was found in the form of cuprite, azurite, and malachite minerals.
They also found out that the ancient Egyptians' blue ink contained scraps of copper most likely from metal workshops near the temples. Their alchemical knowledge was more advanced than they're commonly credited for.