References

Even in regard to the poorer quality tiles at the Mogao grottoes, coating with consolidants has greatly improved their wear resistance. Onsite experiments also suggest that consolidation can be easily carried out in the field and that use of either coating material satisfies a fundamental conservation principle of retaining the original appearance of materials.

In addition, polyurethane coating was shown to increase the ability of tiles to withstand freezing and thawing with less deterioration of the surface.

In March 1988, an evaluation team from the Unesco World Heritage Committee visited the Mogao grottoes for two days. Team members raised several issues concerning the conservation of the site and made a number of suggestions. The protection of the floor tiles was one of the items mentioned in their report (Unesco 1988: Item 94). They pointed out that replacing the floor tile with concrete would change the original grotto structure and would also disturb the microenvironment inside the cave. Environmental monitoring was suggested for caves with original floor tiles as well as for those with concrete floors. The report also proposed that the ancient floors be conserved by placing mats and other protective pads in areas that incur heavy traffic.

In accordance with the evaluation team's suggestions, environmental monitoring of caves with both types of floors are being conducted. As for floor mats or pads, it was felt that these may be useful for tile protection but would limit visitors' ability to appreciate the aesthetic tile patterns of the floors. The most suitable approach, therefore, is still to treat the tiles with consolidants and other protective coating materials.

1 Additional information was not available on the chemical nature and source or manufacturer of consolidants tested. Ed.

1993

Gao Nianzu, Jia Ruiguang, and Wang Jinyu

Report on the restoration of decorated floor tiles found in the Mogao grottoes, Dunhuang (in Chinese). Grottoes Conservation, special edition (in Chinese) 2:288-95.

Unesco World Heritage Committee

Mission Report: People’s Republic of China, 21 March-5 April 1988. World Heritage Convention, Unesco. Rome: International Centre for the Study of the Preservation and the Restoration of Cultural Property (iccrom).