Figure (1): Excavated lacquered wood components. Photo by Xinhua News Agency reporter Li He
Figure (2): Unearthed bronzes. Courtesy of the archaeological excavation team of Wuwangdun Tomb
Figure (3): Unearthed lacquered wooden box. Courtesy of the archaeological excavation team of Wuwangdun Tomb
Anhui Huainan Wuwang tomb archaeological excavation site. Photo by Xinhua News Agency reporter Huang Bohan
In April, the weather in Huainan City, Anhui Province, sometimes sunny, sometimes rainy, and the humid air is full of the message of the germination of all things. The north is according to Shungeng Mountain, the south is the open flat land, the west side is the Wabu Lake, and it is located in the archaeological site of the No. 1 tomb of Wuwangdun in Xuwa Village, Sanhe Town, Huainan, and the archaeologists are busy in an orderly manner.
As this large-scale, highest-level, and most complex large-scale high-level tomb of the Chu State gradually revealed its true face, the Chu culture became more and more vivid.
High-level layout, paving the "long road"
Since the official launch of the archaeological excavation of Wuwangdun in 2020, a cultural relics protection team composed of multi-university and multidisciplinary experts has been immediately formed. At the same time, a series of archaeological excavation supporting facilities such as the main tomb protection greenhouse, cultural relics warehouse, and archaeological laboratory have also been rapidly completed.
Plan before you act. Zhang Zhiguo, research librarian of the Archaeological Research Center of the State Administration of Cultural Heritage and person in charge of cultural relics protection of the archaeological excavation project of Wuwangdun Tomb, introduced that before the archaeological excavation work began, according to the type of cultural relics unearthed from tombs of similar eras, the cultural relics unearthed from Wuwangdun No. 1 Tomb were predicted, and on this basis, a multidisciplinary research plan for the on-site protection of unearthed cultural relics was formed.
One of the biggest questions was quickly put in front of everyone. Because the cultural relics in the coffin are soaked in water all the year round, and the coffin cover plate and bamboo mat above the water surface are also in a state of saturation, how to carry out timely emergency protection of the unearthed cultural relics?
"The archaeological excavation of Wuwangdun Tomb is very different from Sanxingdui, Sanxingdui archaeological excavation is in a relatively stable environment and can be extracted slowly, but Wuwangdun Tomb is not good. Gong Decai, a professor at the University of Science and Technology of China, said, "The tomb of Wuwangdun has been soaked in water for a long time, and once it is out of the saturated environment and in direct contact with oxygen, the wooden figurines, lacquerware and other cultural relics will soon be curled, warped, discolored, and even greatly shrunk and deformed." We need to extract the artifacts as quickly as possible and send them to the laboratory as quickly as possible, while preserving as much information as possible. ”
The grave pit is square, and there is a slope tomb road to the east of the grave pit, and there are 21 steps on the four walls of the grave pit. Under the layers of compacted earthfill, a nine-chamber coffin appeared in front of the archaeological team. A huge bamboo mat is covered with a coffin cover board, and under the bamboo mat, square timbers and thin boards alternate in turn to form a multi-layer protection. Zhang Zhiguo said that by using the high-density resistivity method, the layout of Wuwangdun No. 1 Tomb gradually became clear. The wooden coffin room adopts the "Asia" shaped structure, with a total of 9 rooms, which is the first time to see in China at present, and the structure is clear and definite nine-chamber Chu tomb.
The bamboo mat quickly entered the protection of the archaeological team. Zhang Wenjie, a professor at Xiamen University's School of History and Cultural Heritage, recalls that after the excavation was completed, the first thing that caught his eye was the bamboo mat laid on the coffin cover. "Even though more than 2,000 years have passed, bamboo mats in some areas are still able to take on a yellow hue. ”
Decayed, mutilated, cracked, thousands of years of underground life have made most of the bamboo mats fragile.
How to safely and efficiently carry out temporary reinforcement and emergency protection of bamboo mats? Menthol temporary solidification technology provides a solution. This pioneering achievement, invented by the team of Professor Luo Hongjie of Shanghai University and with independent intellectual property rights in mainland China, is the first in the world. Menthol can be pre-reinforced to a certain extent for fragile cultural relics to ensure the safe transfer of cultural relics to the laboratory. "And there is no residue of the material after it naturally evaporates in the air. Zhang Zhiguo said.
However, new problems followed. The environment of Wuwangdun Tomb is humid, and after the bamboo mat enters the laboratory, if menthol is allowed to volatilize naturally, the water in the bamboo mat will also evaporate rapidly, resulting in warping and cracking of the water-saturated bamboo mat. After repeated experiments, Zhang Zhiguo found that by adding alcohol, heating and other methods, menthol can be effectively removed, and the bamboo mat can be ensured to be in a saturated state, which not only ensures the safety of cultural relics, but also facilitates the follow-up of a series of protection treatments such as pollutant cleaning, iron removal, reinforcement, drying and shaping.
At present, the largest area of ancient bamboo mat extraction work carried out at home and abroad, it quickly achieved results. The archaeological team adopted the method of strip extraction, extracting the longest bamboo mat of about 7.5 meters, with a total area of more than 200 square meters, forming a set of technical methods for on-site reinforcement and extraction, packaging and transportation of bamboo mats and indoor stability protection.
Classification of "rescue", but also need to "prescribe the right medicine"
Writing is the most mysterious symbol of history, witnessing the changes of time and telling the ancient stories and magnificent legends of the land of Chu more than 2,000 years ago. However, the discovery of words is not as easy as imagined.
Infrared camera technology can clearly reveal the text hidden on the black coffin cover. What excites Zhang Zhiguo is that more than 100 sentences and nearly 1,000 characters of ink script have been found and collected on the cover plate of the coffin chamber of Wuwangdun No. 1 Tomb, which is a typical Chu script. Combined with the textual content and the judgment of the archaeological situation, there are the orientation and sequencing of the coffin cover plate, the functional partition of the coffin chamber, etc., which is of great significance for the study of the construction process of the tombs of the Chu State, the official system, and the title of famous objects.
The protection of the coffin cover is also of great significance. Gong Decai said that with the gradual exposure of the coffin cover, through water spraying and covering plastic film, non-woven fabric and other measures, the coffin cover is in a saturated state, reducing the cracking and deformation of the coffin cover caused by the rapid evaporation of water. "In the process of extracting the coffin cover, the fragile and cracked parts are reinforced through menthol, gypsum bandages, splints and other reinforcing materials, and the stressed parts are buffered and supported by pearl cotton and bubble film, so as to reduce the damage of cultural relics in the lifting process and ensure the smooth development of archaeological excavation and research. ”
As for the ink script on the coffin cover, Zhang Zhiguo handled it very carefully. "We use a reversible rosin alcohol solution to protect the ink books from damage during the extraction, transportation and storage of the coffin covers. Zhang Zhiguo said that after the coffin cover plate cultural relics are transported to the storage site, the wood is treated with antibacterial, mildew and moisturizing treatment in a timely manner, and the mold breeding and water saturation of the coffin cover are monitored, so that the coffin cover plate can be safely and stably preserved and protected.
During the Spring and Autumn Period and the Warring States Period, the Chu State had formed a very high lacquered wood production process. Many lacquered wood artifacts unearthed this time, including wooden figurines, lacquerware, tomb beasts, etc., are lying quietly in the archaeological laboratory not far from the archaeological excavation site. In the archaeological laboratory, the reporter saw pieces of beautifully patterned and well-made lacquerware soaked in water. "It's deionized water, it's like giving a bath, it has a cleansing effect. Zhang Wenjie said.
"The on-site protection process of lacquered wood mainly includes trace information collection and cleaning processing. Zhang Zhiguo said, "The cleaning process is mainly soaked in deionized water to soften and soak out the impurities, and then cooperate with a soft brush for deep cleaning between the gaps, and add a small amount of surfactant for cleaning if necessary." If there are gold-painted, lead-painted and other processes on the surface of lacquered wood, according to the preservation status of the painting, it can be properly reinforced before soaking in water. ”
"After cleaning, the artifacts are dehydrated, that is, soaked in a special chemical solution, so that the potion 'melts' into the interior of the artifact, and instead of water, it supports the pore structure of the wood. Gong Decai said that this set of "diagnosis and treatment treatment" is the mainland's original glyoxal method, from Mawangdui to the tomb of Marquis Zeng, from the tomb of Dingtao Han to the tomb of Wuwangdun today, tens of thousands of lacquered wood vessels in this set of "treatment" to save the life of the utensils in the turbulence, glowing with new vitality.
The analysis and research of some unearthed lacquerware shows that the lacquer used in the lacquerware unearthed from the No. 1 tomb of Wuwangdun is Chinese lacquer, and the lacquer paint pigment is different, the vermilion lacquer pigment is cinnabar, the reddish-brown lacquer pigment is iron red, the black lacquer pigment is carbon black, and the yellow color pigment is a mixture of orpiment and realgar.
Technology empowerment, multi-disciplinary, multi-platform collaboration
When the bronze chimes strike the last note of a thousand years ago, the dancers in the costumes dance to the beat of the drums and the sound of the piano...... More than 2,000 years later, a sleeping underground "band" of the Chu State was reawakened. When the archaeological team extracted the figurines from the mud pile in the coffin, the silk clothes attached to their bodies were also extracted. Zhou Yang, deputy director of the China National Silk Museum, said that silk is organic and difficult to preserve. The silk unearthed in water shows a rotten state like wonton skin. However, the "wonton skin" contains a large number of silk relics and related occurrence information.
"For the conservation of silk excavated from archaeology in the humid environment of the south, the process from saturation to dryness can be said to be a matter of life and death. Zhou Yang said. The cultural preservation team composed of the China National Silk Museum is responsible for the emergency rescue of the unearthed silk.
Silk needs to be moisturized during emergency protection, but excessive water flow will change the state of the textiles on the "clothed figurines". Faced with a dilemma, the cultural preservation staff chose to spray water and moisturize and wrap with film. In order to increase the strength of silk, the cultural preservation personnel use the method of silk protein reinforcement to "thread the needle" from the molecular level, and "sew and splic" the broken molecular bonds of silk. "Since silk protein is the main component of silk, this homologous reinforcement method can effectively avoid the subsequent degradation of the reinforcement material and damage to the cultural relics, which is also our original method. Zhou Yang said.
During the on-site excavation, Zhang Zhiguo also recorded such a critical moment. "When the coffin cover was lifted, there was water underneath, but there were dozens of clusters of plants of various sizes floating on the surface of the water in the east room. After salvage it, after preliminary analysis, it contains plums, plums, chestnuts, melon seeds, lotus seeds and other melons and fruits, as well as crops such as rice, millet, millet, etc., and it is preliminarily determined that the burial period of the tomb owner should be in the summer or autumn when the plants are ripe. Zhang Zhiguo said.
Animal and plant archaeology is an important part of modern archaeology, and it is also a concentrated embodiment of the multidisciplinary integration characteristics of contemporary archaeology. Through animal and plant composition analysis, protein analysis, bone age detection and other means, archaeologists can accurately locate the age and identity information of cultural relics, and distribute "ID cards" to these elderly "underground residents". Now, Zhang Zhiguo said, the plant clusters are being sealed in plastic film and temporarily stored in the low-oxygen sterilization warehouse of the archaeological laboratory, waiting to be sorted out and studied in batches.
The valley rain has passed, and the beginning of summer is coming. As the weather gets hotter day by day, the environment of the burial chamber will change dramatically. This is an extremely severe test for the cultural relics and archaeological team members on the site.
In order to create a relatively stable environment for the cultural relics that are still "waiting", the project team is preparing to build a "three-control system" for the tomb. Zhang Zhiguo explained that the "three controls" are temperature control, humidity control, and oxygen control. "We are about to carry out the construction of the atomization sprinkler system, which greatly reduces the workload of manual humidification of the staff, by spraying the ice water mixture regularly, not only can reduce the temperature of the room, but also can effectively increase its humidity, by filling the coffin with nitrogen, we can reduce the oxygen content of the air in the coffin by 50%, effectively delaying the oxidation rate of cultural relics, by controlling the archaeological site environment, we can retain as much original information as possible, and also win valuable time for archaeological excavation work." Zhang Zhiguo said.
Gong Decai said that in the process of archaeological excavation, they have enhanced the ability to discover and analyze the archaeological work of the No. 1 tomb of Wuwangdun through multidisciplinary and multi-platform collaboration, and used new means and tools provided by science and technology to enhance the ability to protect historical and cultural heritage.
Guan Qiang, deputy director of the State Administration of Cultural Heritage, said that in the next step, it is necessary to continue to strengthen archaeology and research, in accordance with the idea of "big archaeology", simultaneously promote scientific and technological archaeology, residue analysis, metallurgy, environment, animal and plant and other scientific and technological archaeology, and make full use of modern scientific and technological means to extract all kinds of information to the greatest extent; At the same time, it is necessary to coordinate and promote the extraction and protection of unearthed bronzes, bamboo and wood lacquerware, silk and related fragile cultural relics to ensure that the unearthed cultural relics are properly protected in the first time. Continue to monitor the stability of graves and coffins and groundwater levels, implement support and reinforcement measures, strengthen the management of archaeological site personnel, and ensure the safety of archaeological sites. (According to People's Daily)