The truth about the rumor that the Forbidden City uses 60 tons of pig blood annually for exorcism

Chu Can, an expert with over 20 years of research on the Forbidden City, stated that the architecture there does contain pig blood but not for exorcism.

A long-standing rumor in China claims that the Forbidden City, the former imperial palace in central Beijing, uses 60 tons of pig blood each year to ward off evil spirits. Folk legends suggest the site is haunted by numerous ghosts, stemming from the countless officials, royal family members, and servants killed within its walls over centuries.

This rumor, however, has been debunked by Chu Can, a researcher at the Palace Museum and an expert in ancient architecture. Chu, who recently launched his book "Sitting Under the Eaves of the Forbidden City: Answering 50 Questions" last month, clarified that pig blood was indeed a component in the palace's construction, but for a practical, not a mystical, purpose.

Chu explained that a mixture applied to the exterior of wooden structures and walls, known as 'dia zhang' (地仗), contains pig blood. Its primary function was to act as a binder, a construction technique employed at the Forbidden City since the Qing dynasty.

The choice of pig blood over that of cows or sheep was deliberate. Cattle and sheep, being herbivores, have blood with less fat, resulting in weaker adhesion. Pigs, as omnivores, possess blood rich in fat and with superior viscosity, making it an ideal binding agent.

The preparation of this pig blood mixture, called 'xueliao' (血料), was an intricate process. Raw pig blood contains impurities like tissue fragments and fibrin, rendering it unsuitable for direct use. Workers first vigorously beat the blood in a basin with a loofah sponge or straw to entangle and remove fibrin strands. It was then filtered through a fine mesh sieve to eliminate other impurities. Afterward, lime water was added to the filtered pig blood and stirred thoroughly. The mixture was then left undisturbed for two to three hours until it coagulated, becoming ready for use.

According to Chu, lime water accelerated the blood's coagulation and reacted with it to create enhanced viscosity. This process yielded a mixture with excellent adhesion, crack resistance, and waterproofing properties.

The 'xueliao' was subsequently combined with brick powder, tung oil, hemp fibers, and flour to form a robust mortar. This mortar was applied to the surface of wooden components throughout the palace, protecting the wood from the damaging effects of sunlight, rain, wind, and insects. Chu concluded, "Using pig blood increased the adhesion and durability of the 'dia zhang' layer. It was a scientific invention of ancient artisans."

The Hall of Supreme Harmony in the Forbidden City. Photo: Bijingdi

The Forbidden City, a royal palace complex in central Beijing, served as the political power center of China for over 500 years, from 1420 to the early 20th century. It housed the Ming and Qing dynasty emperors. Recognized as a UNESCO World Heritage site in 1987, it stands as the world's largest preserved royal palace complex and is China's most visited tourist destination, drawing 18 million visitors annually.

The rumor of haunting is fueled by various tales. In the summer of 1992, during a heavy thunderstorm, many tourists reported seeing images resembling a group of maidservants walking past a blood-red wall. Experts at the time attributed this to the wall paint containing iron oxide, a key element in image formation, causing an optical illusion. However, this explanation was not widely accepted by the public.

Another legend centers on Zhenfei's Well, located in a corner of the palace. It is said that Empress Dowager Cixi ordered the assassination of Emperor Guangxu's favorite concubine there in 1900. Rumors persist of female figures appearing and mournful cries echoing from the well's depths. For safety, the well's opening is now sealed with sturdy iron bars.

The Palace Museum typically closes at 17:00 (5 p.m.), leading many to speculate that the early closing time is due to the palace being haunted at night. Management has refuted this, explaining that staff require time to recheck exhibits daily after visitors depart.