"the presence of prolactin-inducible protein and lactotransferrin indicates the human blood was harvested shortly after childbirth. The blood triggered a reaction forming biomineralised calcium carbonate, which effectively bonded the paint to the limestone rock face, allowing it to withstand extreme heat, rain, and typhoons for centuries. Only a small amount—about 8 millilitres per square metre-was required for this crystallization." https://www.bradshawfoundation.com/china/huashan/blood.php