SIEM REAP – "Learning by doing." This philosophy has guided conservation scientist Prof. Hans Leisen and his team for decades as they work to preserve Angkor Park and historic sites around the world.

Watch the interview on YouTube below:

From mastering technical tools and complex chemistry to sourcing rare restoration materials and overcoming language barriers, Prof. Hans Leisen – head of the German Apsara Conservation Project – has steadily expanded his team’s efforts to protect Cambodia’s ancient monuments since the 1990s.

In this third part of a two-hour interview, Prof. Leisen shares how his team began their work at Angkor Park, the challenges they have faced, and the strategies they have used—or should use—to overcome them.

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Background of the Conservation

The GACP is cooperating closely with the APSARA National Authority and UNESCO. Since 2020, the GACP team has been integrating into the APSARA authority within the framework of the APSARA-GACP cooperation project “German APSARA Restoration and Conservation Project GARCP”.

In 1997, GACP started with research, documentation and conservation of the precious decorations at Angkor Wat.

Conservation requires the exact knowledge of the materials - stone, brick and stuccoes - and the causes of deterioration. In the case of the stone reliefs, the extreme scale formation endangers the floral decorations and the mythological memory of the narrative reliefs.

Step-by-step documentation, research and practical testing paves the way for a sustainable conservation concept that satisfies the aesthetics appearance of the high-ranking works of art and the scientific approach, which is congruent with the current international state of the art.

Conservation materials are optimised and adapted to the needs of the monument. For stone conservation, the tetra-ethoxy-orthosilicate (TEOS) modular system is applied while for the stucco conservation lime products are developed.

At Angkor Wat temple, most reliefs are maintained and conserved. Other conservation work activities are carried out in more than 25 temples in the Angkor Park and beyond for example in Bakong and Preah Ko temples - where stucco remains and sandstone elements are conserved - as well as in many other sites in the Angkor Park, Koh Ker, and Sambor Prei Kuk and on Kulen mountain.

The research of wall paintings and polychrome decorations in the brick temples in Cambodia, construction and stone quarrying techniques are other topics of the Khmer-German GACP cooperation team.

The project is funded by the Cultural Preservation Programme of the German government, the TH Koln and FAKT.