Modern Technology Safeguards Ancient Dunhuang Dunhuang Research Institute | Murals | Dunhuang

Guangming Daily reporter Li Yun, Wang Xiaofei

In early August, the reporter walked into Cave 351 of Mogao Grottoes. Shelves and collection equipment have been erected in the narrow cave, and the digital team of Dunhuang Research Institute is conducting digital collection. The ancient cave in front of us will be frozen in this moment, achieving eternal life in the digital world.

Modern technology not only helps with the immortality of color sculptures and murals, but also promotes the healing and longevity of ancient Dunhuang. In recent years, the "hard power" of the Dunhuang Research Institute in scientific research is obvious to all: a number of scientific and technological achievements in cultural relics protection have been selected into the national "13th Five Year Plan" scientific and technological innovation achievement exhibition, and the first and only national engineering and technology research center for ancient mural protection has been set up jointly with other institutions. It has undertaken a number of national key cultural relics protection projects, and has also gone abroad to provide technical support and Chinese programs for the cultural heritage protection of countries along the "the Belt and Road", such as Kyrgyzstan and Myanmar. In the future, the Dunhuang Research Institute is expected to establish a State Key Laboratory.

Technology weaves the "golden bell cover"

Behind Wang Xiaowei, the director of the Dunhuang Research Institute Grottoes Monitoring Center, is a large screen filled with real-time updated data, full of a sense of technology: the weather conditions of the grotto temple, warnings, real-time tourist numbers, and the current status of cultural relics protection work... The monitoring scope covers the overall environment and microenvironment of the Mogao Grottoes, as well as the cliff and cave body, as well as the exhibition hall, tourists, work, and other situations. It can be said that the dynamics of the grottoes in one room are fully grasped.

In 2022, based on the monitoring and early warning system of Mogao Grottoes, Dunhuang Research Institute launched the Gansu Province Grottoes Temple Monitoring and Early Warning System project.

Photo by Li Yun of the music and dance scene in Cave 220 of Mogao Grottoes/Guangming image

"We monitored 115 caves in Mogao Grottoes and also connected partial data from five grotto temples in Gansu Province, including Yulin Grottoes, West Qianfo Cave, Maijishan, Bingling Temple, and North Grottoes managed by Dunhuang Research Institute. Helping small grotto temples maintain their monitoring and early warning system and analyze data is also one of the significance of being a provincial-level platform." Wang Xiaowei introduced that this project uses technologies such as the Internet of Things and wireless sensors to organically combine the monitoring and early warning work of six grotto temples under the jurisdiction of Dunhuang Research Institute, and incorporates professional institutions such as the Meteorological Bureau and the Earthquake Bureau into the system, providing preventive and rescue protection for grotto temples, as well as tourism opening. Provide data support for work.

In addition to common carbon dioxide concentrations and relative humidity, they also monitor VOCs in caves. Although it has not yet been concluded whether perfume will affect the caves, data can be accumulated in advance to prepare for a rainy day.

In addition to human behavior and natural climate, animals, plants, and microorganisms can also affect the safety of grottoes.

Entering the Biological Laboratory of the Dunhuang Research Institute, I saw a row of transparent bottles stacked on the shelf, containing animals such as snakes, spiders, and lizards. Why collect these specimens? What is their relationship with grottoes? The reporter carefully examined, and the label on the bottle showed that these small animals were collected from various grottoes. Dunhuang Research Institute librarian He Dongpeng explained that animals such as birds, insects, and rodents enter the cave to nest, excrete, and scratch; Plant roots and branches grow into the structure of the mural; Microbial growth and erosion can cause damage to murals, so prevention and control measures should be taken.

In a corner of the laboratory, there were many densely packed black spots moving inside a box. Upon closer inspection, it turned out to be beetles. "This is the insect we raised to study the local beetle family. In the past few years, with increasing rainfall, this insect bred in large numbers and crawled into caves in small numbers. Currently, chemical pesticides are used to kill and trap them, trying to control their population within a reasonable range." He Dongpeng explained to reporters.

Upon arriving at the Emergency Command Center of the Dunhuang Research Institute, there is another huge screen with different monitoring images distributed in different areas. There are both uninhabited non open caves in front of the door, bustling tourists with their families, and scenes of duty rooms in caves such as Maijishan, as if inviting the "Thousand Eyed Guanyin" to sit down.

Dunhuang actively carried out the construction of "Ping An Grottoes". In May of this year, the security upgrade and renovation project of Mogao Grottoes was completed, and the comprehensive connection of the security systems of one courtyard and six grottoes was achieved. A more and more dense "golden bell cover" was erected above the grotto temples.

"There are over 780 cameras in the Mogao Grottoes, and there are over 1300 video images linked to five other grottoes, including Yulin Grottoes." Zhang Shuai, Deputy Director of the Security Department of the Dunhuang Research Institute, explained that the security department strictly implements 24-hour dual person and dual post duty. When someone approaches the restricted area and triggers an alarm, drones, vehicles, and personnel will be immediately dispatched. "It takes only two to three minutes to arrive at the scene in the cave area, and five to six minutes in distant places." Zhang Shuai proudly said, "Conservatively speaking, our security system should be among the top five in the national cultural relics system." In the future, the Dunhuang Research Institute also hopes to apply to become a cultural relics security training base in the province, promoting advanced security to more cultural relics protection units. "Experience prevention.

Digital collection site for murals in Cave 148 of Mogao Grottoes. Provided by Dunhuang Research Institute

The security guarantee system not only safeguards the safety of cultural relics, but also protects the safety of tourists and employees. "We will integrate existing security, fire protection, electrical circuit systems, etc. into the digital twin model, facilitating internal hazard investigation and risk classification control."

The security system also integrates data from the hospital's monitoring center and tourist reservation system, and the data is shared with the Jiuquan Fire Brigade and the Dunhuang Public Security Bureau to minimize information silos. After the system upgrade, the efficiency of police monitoring lost or lost items by tourists has greatly improved. "From the original three or four hours, the problem can be solved in as fast as five minutes now," said Zhang Shuai.

Experimental forging of "talismans"

On a computer display screen, the digitally simulated mural of Cave 254 in Mogao Grottoes, titled "Prince Sa Zuo Ben Sheng", appears as if it had just been painted, bright and bright, in stark contrast to the mottled and weathered original mural. Chai Bolong, Deputy Researcher of the Dunhuang Research Institute, introduced that this is the first mural restored using multispectral technology in the Mogao Grottoes. Under ultraviolet and infrared light, details such as mural lines and the use of organic pigments that are invisible to the naked eye appear, just like the anti-counterfeiting label of the Chinese yuan under ultraviolet light. By using multispectral technology, the pigment layer and painting techniques of the mural can ultimately be scientifically restored rather than subjectively, restoring the original appearance of the mural. And this method is non-destructive, non-contact, and will not cause damage to the mural.

Chai Bolong pointed to the image of "Five Hundred Thieves Becoming Buddhas and Marriage Stories" in Cave 285 on the screen and said, "In fact, the ancients painted many wonderful details at that time, such as the blood sprayed under ultraviolet light, which can be vaguely distinguished. You can also see the traces of modifications made by the ancients during painting, such as the position of the tiger's tail being modified in the wall painting of Cave 254." He enthusiastically shared.

In addition, multispectral analysis can also help identify the distribution positions of different pigments in murals. "Many color changing murals we see are all black, but what kind of pigment were they before turning black? By comparing the standard database of pigment multispectral images, we can determine their true identity, such as lead or indigo."

Following the scientific researchers wearing white coats, the reporter walked between the various laboratories of the Dunhuang Research Institute's Protection Research Institute, with a variety of instruments and equipment that were overwhelming. Posters on the wall record the fruitful achievements of the Dunhuang Research Institute in scientific research.

What materials and techniques were used to make the murals in Dunhuang Grottoes? How to prevent murals from getting moldy? How to protect murals in situ With the help of modern technologies such as scanning electron microscopy, Raman spectroscopy, and X-ray fluorescence spectroscopy, the secret of Dunhuang murals that have been shrouded in dust for thousands of years has gradually been found.

Entering the first multi field coupling laboratory in the field of cultural relics protection in China, which is about two floors high and covers an area of over 3000 square meters, one can witness all four seasons in one moment: in the winter warehouse, samples from the Suoyang City site are covered in white snow; In the wind and rain chamber, samples from the North Caves Temple in Qingyang experienced "wind and rain"; In the summer warehouse, the samples taken from the Qin Dongling site are the most weathered, with cracks on the surface crisscrossing like ravines. "This sample has undergone an accelerated simulation of a complete annual cycle. At the beginning, its surface was relatively flat and smooth. After experiencing an annual cycle of snowfall, rainfall, and weathering, it has already developed some obvious diseases." Zhang Bo, deputy research librarian of the Dunhuang Research Institute of Conservation, introduced that these samples were not taken from the site itself, but were made from the original samples around the site or using traditional techniques.

The multi field coupling laboratory has advantages such as controllable time, adjustable accuracy, the ability to conduct multi field coupling simulations, and full-scale sample simulations. Here, we can simulate the appearance of immovable cultural relics after being subjected to various natural conditions in a short period of time, providing data for the use and research and development of protective techniques and materials, and revealing the reasons for the "illness" of earthen relics. Three warehouses can be used together to simulate temperatures ranging from minus 30 ℃ to 60 ℃, relative humidity ranging from 10% to 90%, as well as various climatic conditions such as wind, rain, snow, and sunlight in the area where the earthen site is located throughout the year.

In a multi field coupled laboratory, time can be "accelerated". "For example, in an arid environment, an annual cycle can be simulated in about 40 or 50 days." Zhang Bo said that it is expected to further optimize and compress this simulation process in the future.

The mural restorer is repairing the murals in Cave 55 of Mogao Grottoes. Photo by Wang Xiaofei/Bright Picture

Guo Qinglin, Vice President of Dunhuang Research Institute, said, "I believe there are no bad materials, only bad usage environments and methods. Just like how people treat diseases, which prescription is effective needs to be constantly verified through simulation experiments. A multi field coupled laboratory is a simulation of various" diseases "to test the effectiveness of" prescriptions. ". "We can verify the feasibility of scholars' latest research results in the laboratory; after the materials are developed, we can also provide a detailed user manual for the protection process and materials, such as which sites they are suitable for and how they should be used specifically." Zhang Bo introduced that the PS material independently developed by the Dunhuang Research Institute is used to experimentally study which rainfall intensity reinforcement effects it has for.

Digital opens the "road to eternal life"

Entering the Mogao Cave 351, which is undergoing digital collection, the temperature suddenly drops. Therefore, even if the temperature outside the cave is over 30 degrees Celsius, the collection personnel who gather in the cold cave for a whole day still need to wrap themselves in thick coats. Inside the cave, the painted Buddha statue hangs its eyebrows, facing the surface of the collection equipment on the steel frame. A thousand years of time, frozen in the "cyber" space at this moment.

"For narrow spaces, we have customized collection equipment that can be assembled and disassembled at will. For large spaces, we have developed automated collection equipment," said Lu Yucheng, a staff member of the Dunhuang Digital Work Team.

The use of machines, the study of objectification, and the wisdom of craftsmanship. A generation of craftsmen has the wisdom of a generation of craftsmen. Ancient craftsmen and painters carved caves and painted murals, leaving us with precious Dunhuang culture; Today, the digital team of Dunhuang Research Institute is using digital technology to support the eternal life of Dunhuang. Since the 1990s, the Dunhuang Research Institute has been exploring digitalization, and the construction of "Digital Dunhuang" has continuously reached new heights.

Lu Yucheng said that at present, "Digital Dunhuang" has collected 290 caves, covering an area of 26000 square meters, 172 caves for making panoramic walkthrough programs, 206 caves for scanning the space structure of caves, 44 colored sculptures for three-dimensional reconstruction, 42134 historical file negatives for digital scanning, and has provided digital technical support for nearly 20 cultural relics protection units in 9 provinces, autonomous regions and cities, including Xinjiang and Xizang.

In 2022, "Digital Dunhuang" was selected as the "Classic Case of Jointly Building a Community with a Shared Future in Cyberspace" at the World Internet Conference. "Among more than 200 cases worldwide, we are the only selected cultural and museum unit," said Su Bomin, the director of Dunhuang Research Institute with pride.

A hundred foot tall building starts from the ground, and nothing can be accomplished in one move in the world. Behind such achievements lies the years of silent cultivation by the collection personnel. Taking Cave 351 as an example, the surface area of the murals in the cave is about 400 square meters. Eight staff members need to spend more than 100 working days collecting data, and the later image stitching will take three to four months.

Entering the image processing office, the room was very quiet, with only the sound of mouse clicks. The members of the digital team are as quiet and determined as the silver poplar outside the window. After completing digital collection in the cave, it is necessary to perform image stitching and positioning correction, color sculpture, and three-dimensional reconstruction of the cave's spatial structure here. It is these people who, day after day, year after year, assemble pictures in front of the computer, like building blocks, to build the magnificent Dunhuang in the digital world.

In 2020, China's first multi site coupling laboratory for cultural heritage protection was officially put into use. Provided by Dunhuang Research Institute

"A person can only splice 20 to 30 images per day, and a wall often has thousands of images. We also need to conduct two rounds of review and modification to ensure that the deformation of the mural is controlled within millimeters." Lu Yucheng introduced, "However, we are developing automatic splicing technology, which is expected to greatly improve splicing efficiency in the future."

Nian Haixia, a member of the digital team, is piecing together pictures on the computer. The reporter watched from the sidelines for a while and then felt the repetition and boredom of the work. "Do you think work is boring?" She shook her head gently and smiled shyly, saying, "Murals are inherently colorful, and the murals I see every day are different. Although I am studying computer science, I also search online to learn about the stories behind murals."

Lu Yucheng has been engaged in digital work for more than ten years, and he candidly said, "The first two years may seem boring, but after three or four years of work, he has become more focused and feels that it is a meaningful document to leave behind for future generations."

Digital Dunhuang is not only for the permanent preservation of Dunhuang's cultural heritage, but also for the sharing of resources within the Dunhuang treasure trove by the whole nation and the world. The Dunhuang Research Institute has been actively promoting the transformation and utilization of digital resource achievements, allowing people around the world to appreciate Dunhuang culture in the cloud.

In 2022, the world's first blockchain based open sharing platform for digital cultural heritage, "Digital Dunhuang · Open Material Library", was launched. 21 types of mural themes and the first batch of over 6500 high-definition digital resource archives from grotto sites such as Mogao Grottoes and scripture cave literature were opened to the world.

"Previously, the international Dunhuang Studies project database of the international Dunhuang academic community only put the original photos on it. Our Dunhuang posthumous works database gives full play to the advantages of expert resources and supplements the full text of the posthumous works." Su Bomin said that the Dunhuang Research Institute is still working with the United Kingdom, Russia and other countries to achieve digital resource sharing and promote the digital return of overseas Dunhuang cultural relics.

The Dunhuang Research Institute is also constantly exploring the latest technology to find more fun, interesting, and lively ways to activate and utilize digital resources in Dunhuang. From the "Cloud Tour Dunhuang" mini program launched during the epidemic period to the "Digital Scripture Cave" of the hyper temporal participatory museum released this year, it has received a high number of clicks. "In the future, we hope that people can easily reach Dunhuang on their mobile phones, such as using VR and other technologies. Perhaps in the future, people can enter every cave in the Mogao Grottoes to visit and explore while sitting at home," Su Bomin said with a smile.

Guangming Daily

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