Editor's note: This is the second article of a series covering the repatriation and protection of China's cultural relics. The process of returning these artifacts signifies a restoration of historical narratives, facilitating a comprehensive understanding of a country's past. CGTN will bring you more on this topic. You can find the previous piece here.

Recently, China's National Museum has unveiled the progressing restoration work on the architectural models of a building complex, which used to be a major venue for the imperial family in the Qing Dynasty to enjoy opera performances, in China's Yuanmingyuan, also known as the Old Summer Palace.

Engaged in the work, Wang Xilin from the object conservation branch at the National Museum's Institute of Conservation, is now busy with the models' cleaning, shape righting and component complement work along with other team members.

Work 'along with the ancients'

Complicated and elaborate, these miniature dioramas set a high threshold for restoration.

"All the roof structures are enclosed, and we can't break or open them up to see the interior," said Wang.

Thanks to modern technologies, the expert said they have been able to scan the models and learn the roofs' internal structure.

Adopting the X-ray imaging technique, they have found the stress points inside the roofs on which they can apply the process of pressing without doing any harm.

The X-ray imaging technique also allowed the restoration team to discover more hidden details.

For example, on the internal support structures of some of the roofs, they have found colored paintings, pointing to the possibility that the materials used may be recycled.

Wang said they have also discovered the ink lines of the manuscript, the craftsman's fingerprints, and redrawn handwritings, among others. These unexpected discoveries have made their restoration work "a journey of creation with the ancients."

Facilitated by laser Raman spectrometer and ultraviolet photography, the team has found the craftsmen adopted a mixture of traditional mineral pigment and synthetic pigment for the paintings.

"Our naked eyes can only see colors like blue, green, light white and light yellow from the lake, land, ornamental stones, and grass and trees," said Wang. "But through ultraviolet photography, we observed there is a deeper color of yellow, which may fade and gradually disappear over more than 100 years, leaving traces at the bottom only."

Besides the technologies above, the restoration work required a lot more technical analysis and testing for other elements of the miniature models, such as materials and adhesive components, to record their preservation status and relevant information, and more importantly, to explore the original process, for "using ancient methods to restore ancient objects," according to Wang.

Researchers of cultural relics from Sanxingdui, dubbed as one of the world's greatest archaeological findings of the 20th century, used high-tech methods for the casting technique at that time.

They used an X-ray defect detector to scan an exquisite bronze altar, and found the altar's parts were cast separately at first.

Taking the bronze figure as an example, Guo Jianbo from Sichuan Institute of Cultural Relics and Archeology, said the figure was composed by the head, hands and body.

"We can see obvious seams, so the parts were cast separately and then joined together by liquid copper casting, which is a typical bronze casting process technology of Sanxingdui," said Guo.

'Revive' history and cultural relics

On April 18, when the International Day for Monuments and Sites fell on, an online exhibition called "Digital Yuanmingyuan" was held as part of a themed activity to show the fusion of modern digital technology and traditional cultural heritage.

It vividly demonstrated the centennial course of the park from how it was devastated by the wars to how it has become a national archaeological site park open to the public.

On the same day, Dunhuang Academy released its latest digital achievement – a digitalized version of the Library Cave.

Integrated with high-definition digital scanning, physical rendering and dynamic lighting, the high-tech museum recreates scenes from the Dunhuang Grottoes, with over 60,000 precious cultural artefacts stored in the caves centuries ago.

It carried out 3D modeling of 21 cultural relics with high definition, and also "reproduced" some of the relics that have been lost overseas.

"We hope that through scientific and technological means, the static value behind the culture can be conveyed to the audience in a more vivid, interesting and real way," said Su Bomin, dean of Dunhuang Academy.

Apart from breaking through the boundaries of time and space, digitalization is the most important preventive protection measure for cultural relics.

The Palace Museum, harboring the world's most complete preserved ancient wooden palace complex with more than 1.86 million pieces of cultural relics and treasures, is China's largest comprehensive museum of ancient culture and art.

So far, it has information resources of all the 1.86 million pieces and 850,000 pieces/sets of cultural relic images, and has collected and produced more than 1,500 high-precision 3D models of cultural relics.

For the protection and renovation of ancient buildings, the museum also produced 3D models of its halls, including the Hall of Supreme Harmony, the Hall of Central Harmony and the Hall of Preserving Harmony. High-precision panoramic images of all open areas have been collected as well. It has also collected more than 8,500 hours of video and audio resources, covering aspects such as ancient building repair, cultural relic restoration, history narration, and academic conferences.

The museum has utilized digital technologies in its online projects, known as "The Digital Relics Collection," "The Digital Treasure Hall" and "The Panoramic Forbidden City," making cultural resources "alive."