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Geosciences Support Monument Conservation – 25 Years of German Apsara Conservation Project

The Angkor region was the center of the historic Khmer kingdom, now Cambodia, from the 9th-15th centuries. The Angkor Park, with over 200 temples, has been a UNESCO World Heritage Site since 1992. The largest and most famous temple is the mountain temple of Angkor Wat, dating from the first half of the 12th century. It is built of sandstone over an artificial mountain with a substructure of laterite.

Angkor Wat is completely decorated with stone reliefs and houses the famous bas-reliefs depicting mythological scenes from Hinduism and the military feats of its builder God-King Suryavarman II on about 1.800 m².

The building stone of the temple is a clay-bound arkose. After more than 870 years of unprotected exposure in tropical climates, the stone shows some alarming weathering damage. Especially the weathering form of "scaling" threatens reliefs and building stones.

The German Apsara Conservation Project active for 25 years aims at the scientific conservation of sculptured surfaces at the temples in Angkor and other historical sites in Cambodia. Based on geoscientific investigations, the requirements for a conservation concept including materials and application could be formulated and adapted materials developed. A multidisciplinary project approach is followed together with other experts from engineering, microbiology, chemistry, and conservation sciences. Students from German and international universities are also involved.

A successful conservation concept needs highly trained practitioners for its implementation. About 20 Cambodian conservators work in the GACP, all trained in the project and meanwhile transferred to the Cambodian conservation authority APSARA.


Hans Josef W. Leisen1, Esther von Plehwe-Leisen2
1CICS TH Koeln, Germany; 2LPL Stone Conservation Köln, Germany
GeoMinKöln 2022