Inks containing lead were likely used as drier on ancient Egyptian papyri

Analyzing 12 ancient Egyptian papyri fragments with X-ray microscopy, researchers were surprised to find previously unknown lead compounds in both red and black inks and suggest they were used for their drying properties rather than as a pigment. A similar lead-based 'drying technique' has also been documented in 15th century European painting, and the discovery of it in Egyptian papyri calls for a reassessment of ancient lead-based pigments.

source https://www.sciencedaily.com/releases/2020/10/201026153959.htm