Duplicate to ‘maintain the holistic state’ of ancient murals

By WANG YUNQU / 10-19-2023 / Chinese Social Sciences Today

A mural in the Mogao Cave 254 depicting Sakyamuni defeating Mara with wisdom and the Bhumyakramana mudra Photo: DUNHUANG ACADEMY

“Xianzhuang Moxie” [lit. present state replication], refers to the holistic replication of artworks based on their present state, or holistic state. It is a process that involves careful scientific analysis and relies on artistic understanding. It is not merely a “scientific replication” of works, as it necessitates artists to possess not only a deep cultural understanding but also the ability to express their artistic vision. Holistic replication imposes high demands on artist’s overall artistic cultivation and understanding of historical relics.

‘Holistic state’

In his book Theory of Restoration, Cesare Brandi distinguished three phases of time for a work of art. The first is the “duration” of the creative process, which is carried out by the artist and ends with the completion of the work. The second is the “moment” of the work of art’s appreciation as such by the conscious awareness of the observer (who assumes the duty of passing it on to the future). The third is the “interval,” the historical interval of time that elapses for the work until the present.

In the complex practice of holistically replicating ancient cave murals, every effort is made to preserve and faithfully reproduce the various traces and influences of this “interval” on the replica. As Wu Hong stated in his article “The Return of the Physical Object: The ‘Historical Materiality’ of Fine Art:” “we should not view these changes as regrettable ‘losses in history,’ because they also reveal the recreation of history. Therefore, the study of the historical materiality of fine art should not only reconstruct the original condition of a work, but also trace the continuous transformation of its form, meaning, and context throughout history.”

Understanding the holistic state of a mural entails recognizing that it is inseparable from its external environment. When a mural is removed from its original cave and displayed in a museum, it undergoes distinct visual changes and evokes a different artistic experience. The objective of holistic replication is to faithfully reproduce the appearance and ambiance of the mural as it exists within its original cave setting.

The internal spatial structure of the holistic state comprises five components: the support, fundamental layer, pigment layer, deterioration layer, and dust layer. The support refers to the substrate on which the mural is situated. The fundamental layer, positioned between the support and the pigment layer, serves as “the canvas” for painting. It is often coated with white powder, and in earlier times, red soil was also applied. The pigment layer is where the pigments were applied to create the artwork. The deterioration layer encompasses the historical traces such as discoloration, natural weathering, and human damage. The dust layer refers to the natural accumulation of sand and dust particles on the surface of the mural, blending with its other layers. The internal spatial structure determines that research on holistic replication should not only consider the surface of a mural but all five layers as a whole. 

Natural and anthropogenic threats

Throughout history, the holistic state of murals has been shaped by both natural forces and human activities. In China, many historical caves were dug in mountains. Fissures in the Mogao Grottoes in Dunhuang were the result of tectonic activity and erosion. Exploration and reinforcement of the Mogao Grottoes began in the 1950s and 1960s. The weathering of the rock mass poses a significant threat to the fragile support layer of murals. Wind and sand also have a significant impact. In the case of the Mogao Grottoes, sand particles that enter the cave adhere to the surface of the murals, abrading the pigment layers. 

Prolonged light exposure is also an enduring threat to the murals. For example, cinnabar darkens after long exposure to light, and lead-based pigments tend to oxidize to brown-black lead dioxide when exposed to air. Open-air murals are more prone to color changes and fading compared to those located within caves. In the case of the multi-layered murals like those found in Cave 263 of the Mogao Grottoes (with an earlier mural dated to Northern Wei Dynasty covered by a Western Xia mural), the Northern Wei mural retained its original color when the Western Xia mural was removed, because it was not exposed to light.

Human activities constitute the second major factor affecting the holistic state of murals. During the mid-Tang Dynasty, the An Lushan Rebellion broke out, and the Tibetan kingdom took advantage of the ensuing chaos to occupy Dunhuang. During its rule, certain caves suffered severe damage caused by the Islamic occupiers. Furthermore, a lack of knowledge in cultural heritage preservation and improper restoration measures can also cause irreversible damage to murals. In certain early instances of mural protection, excessive cleaning of the dust layer disrupted the “microenvironment” of the fundamental and pigment layers, causing problems such as weakening the support. Overseas looters and the use of fire for cooking inside caves have left many murals heavily damaged. Present-day visitors can also cause instantaneous changes in temperature, humidity, CO2 levels, and other factors, leading to “fatigue aging” of the murals. This, in turn, can result in pigment layer separating from the underlying layers, causing damages such as micro-cracks, which ultimately impact the condition of the murals.

Mogao Cave 254

The Dunhuang murals are located in the heart of the desert, which provides unique natural conditions for their preservation. The Mogao Grottoes currently consist of 735 caves, covering an area of 45,000 square meters with over 2,000 colored sculptures. Cave 254 is the most representative meditation cave from the Northern Wei period, excavated between 465 and 500 CE. It is the earliest cave with a central pillar in the Mogao Grottoes, covering an area of 62.04 square meters. A clear window two meters high on the east side allows light to enter the cave. The cave consists of an anterior hall for worshipping and a central stupa for circumambulation. The north wall of the cave is adorned with murals depicting classic Buddhist stories such as King Shibi offering his flesh to save a pigeon from a preying falcon and Sakyamuni helping his half brother, Prince Nanda, to renounce his worldly desires and to devote himself to Buddhist practices. The south wall features murals depicting Prince Sattva sacrificing himself to feed a hungry tigress and her cubs, as well as Sakyamuni defeating Mara with wisdom and the Bhumyakramana mudra.

The Mogao Grottoes benefit from an arid climate, with an average annual temperature of about 11°C and an average annual precipitation of approximately 23 millimeters. The high evaporation rate, reaching about 3,500 millimeters annually, further contributes to the long-term preservation of the murals. Cave 254, located in the middle section of the Mogao Grottoes, largely avoids the threat of the Daquan River (about 150 meters away), as well as the potential damage from underground water seeping into the wall. The ideal geographical location has ensured that Cave 254, after 1600 years, still retains its vibrant colors, making it one of the best-preserved caves from the Northern Wei period in the Mogao Grottoes.

Despite the favorable natural environment, human factors have greatly influenced the condition of the murals in Cave 254. Before the establishment of the People’s Republic of China, shepherds used to cook with fire inside the cave, resulting in obvious soot marks on the walls and ceiling. Furthermore, as the murals attracted more public attention, the number of visitors inevitably increased. The total number of visitors to the Mogao Grottoes in August 2012 was 2.1 times that of August 2011, with 241 visitors specifically visiting Cave 254 in August 2012.

The holistic replication of murals relies on a range of scientific data, including schematic diagrams of the micro-meteorological monitoring system, the comparative analysis of relative humidity, and data from AutoCAD surveys, portable Raman spectroscopy and portable digital microscopes. This data is essential to ensure the precise duplication of the original murals. 

During the replication process, it is essential to maintain the “blue” classical aura and the distinctive “rough style” of the Northern Wei period. Additionally, as Cave 254 is covered with a thick layer of dust, special attention should be paid to capturing its “dusty appearance.” The depiction of the “dust layer” represents the final step, adding a touch of modernity to the replica. The artistic solution for the “dust layer” does not follow a standardized process but requires the artist to comprehensively handle the dust, residue, and mixed pigments generated during the copying process, and process them artistically. If the artificial traces during the copying process are too obvious, the artwork can be taken outdoors, a practice that simulates exposure to the wind and sun of the cave environment. The depiction of the “dust layer” represents a crucial transition of the holistic replica from “science” to “art.” Data will never replace the human touch. Cultural understanding and artistic expression are the key to entering a viewer’s heart.

Significance of holistic replication

Holistic replication offers the opportunity to capture the current appearance of murals with remarkable accuracy, achieving a faithful “copy” of the original. The presentation and deterioration of mural pigments can vary based on environmental factors, preservation conditions, and the age of the murals. Holistic replication preserves the aesthetic beauty of murals in each stage for future viewers. This approach fills a crucial gap in the scientific study of traditional paintings.

Over the past century, efforts to protect ancient murals have become more systematic and professional. Measures such as wind and sand control in the Mogao Grottoes and the implementation of temperature and humidity control systems inside the caves have been employed. However, the significant increase in visitor numbers has posed new challenges to mural preservation. Holistic replication allows more people to appreciate the art of murals without visiting the originals, thus serving as an effective means of protecting ancient murals. This practice also makes it possible to bring together murals from different regions, periods, and cultural backgrounds, thereby creating a comprehensive and mobile “art gallery.” 

Wang Yunqu is an experimentalist from the College of Fine Arts at Capital Normal University.