Huashan rock art durability attributed to ancient use of blood

Researchers have identified the secret behind the longevity of the Huashan rock art in China’s Guangxi province. The ancient red murals, located in the Zuojiang River Valley, have survived for approximately 2,000 years despite extreme heat, high humidity, and heavy monsoon rains.

A study published in the Journal of Archaeological Science reveals that ancient artists used a sophisticated technique involving a thin layer of artificial mortar beneath the pigment. This base, ranging from 1 to 150 micrometers in thickness, was composed of calcium carbonate, clay, silicates, and sulfates.

Crucially, the analysis found that blood—both human and animal—served as a vital organic binder. The proteins in the blood, such as albumin and fibrinogen, reacted with the limestone surface to create a biomineralized calcium carbonate layer. This process effectively encapsulated the pigment, preventing it from peeling or washing away over millennia.