Conservation of wall paintings at Sigiriya

Objectives

The Ancient City of Sigiriya was inscribed on the World Heritage List in 1982. It is a major archaeological site with a history that extends from prehistoric times to the eighteenth century, but is best known for its outstanding wall paintings dated to the fifth century AD. These paintings are located in a recess on the western face of Sigiriya rock about a hundred meters above ground level and are exposed to gradual decay (discoloring and apparition of whitish clouds on the surface).

This project aimed to:

• assess the state of preservation of the wall paintings at Sigiriya;
• identify the causes of their decay;
• provide recommendations for appropriate conservation methods and environmental monitoring procedures.

Results

An expert mission took place at Sigiriya in May 2011.

The investigations carried out during this mission clearly showed that while some deterioration phenomena existed, the paintings were not under severe imminent threats of decay. It also appeared clearly that there was an overall critical lack of knowledge and understanding of the original techniques and materials, the deterioration phenomena, the environmental impact and the behavior of previous conservation treatments: for example, gypsum was identified for the first time in the white/pinkish veil, and the widespread pink discoloration seemed to be related to previous repairs.

The two key recommendations of the mission were:

1. Urgent need for scientific investigations using on site non-invasive techniques such as diagnostic imaging and spectroscopy as well as environmental monitoring, in order to better understand the techniques and original materials of the paintings, the products of alteration and the overall state of preservation of the paintings;
2. Avoid any immediate remedial conservation approach (chemical conservation treatment) as long as the requirements of the above given recommendation are not fulfilled, since any action not supported by scientific investigations could be detrimental to the condition of the paintings.