When ancient Egyptians put pen to paper—or, more accurately, ink to papyrus (纸莎草纸) —they took steps to ensure that their words would last forever, a new study suggests. Researchers from the University of Copenhagen have found that ancient scribes (抄写员) likely added lead to their inks to help their writing dry. More than 1,000 years later, reports Cosmos magazine, 15th-century European artists employed lead as well. According to the London National Gallery, lead-based pigments (颜料) found in many Old Master paintings are "known to aid the drying of paint films."

According to a statement from the University of Copenhagen, the study's authors analyzed 12 papyrus pieces dating back to between 100 and 200 C.E., when Egypt was under Roman control. The team used X-ray microscopy to determine the raw materials used in different inks, as well as the chemical structure of the dried ink attached to the ancient paper. Ancient Egyptians began writing with ink—made by burning wood or oil and mixing the resulting material with water—around 3200 B.C.E. Typically, scribes used black, carbon-based ink for the body of text and reserved red ink for headings and other key words in the text. Though black and red inks were most common, shades of blue, green, white and yellow also appeared in ancient texts.

The researchers write that the Egyptians created red inks with iron-based combinations—most likely natural earth pigments. The team also identified the presence of lead. They were bowled over that there was no lead white or other combinations that would typically be present in a lead-based pigment. Instead, the ancient ink's lead pigments appeared to wrap around the papyrus cell walls and iron particles (微粒). The resulting effect looked "as if the letters were outlined" in lead. This find indicates that the ancient Egyptians invented a system of adding lead to red and black inks specifically for the purpose of sticking the words to paper.

The 12 analyzed papyrus pieces are part of the University of Copenhagen's Papyrus Carlsberg Collection. The documents originated in Tebtunis, the only large-scale institutional library known to have survived from ancient Egyptian times.