Using portable moisture meters and paper pulp poultice to investigate moisture and salt distribution in rock-cut bas-reliefs Bete Golgotha, Lalibela (Ethiopia)
This study investigates the deterioration of carved bas-reliefs on the interior walls of a medieval rock-cut church in Lalibela, Ethiopia. Bete Golgotha is one of two church in the Lalibela church complex that has bas-reliefs of saints on the north and south walls of the church. The bas-reliefs on the north wall are affected by surface material loss due to flaking, while the bas-reliefs on the south wall, conversely, are in very good condition. The aim of this paper is to determine the cause of localized deterioration on stone structures using non-destructive techniques. Surface moisture content and salt distribution were measured along a vertical transect on the bas-relief to determine if moisture ingress and salt weathering were the main causes of the damage that was observed on the north wall. Moisture distribution was assessed using a Protimeter Surveymaster, an Infrared camera and a Moist 350 B microwave moisture meter. Soluble salts were extracted from the bas-reliefs using paper pulp poultice and the concentration of soluble salts absorbed by the poultice was measured using a conductivity meter and an Ion Chromatographer. The results from the IR camera and Moist 350 B showed a similar distribution of surface moisture on the north and south walls. An overall higher Protimeter reading was measured on the north wall. This was due to the presence of salts, which are known to increase Protimeter readings on stone surfaces. This corresponds with the results of the salt extraction test, which showed that a higher concentration of soluble salts was present on the surface of the north wall. Therefore, we can conclude that the deterioration of the north bas-reliefs may have occurred as a result of salt weathering.
Source (book)
Monuments in Monuments : conference proceedings
Historic Environment Scotland , 2019
p. 43-52
Publication type
External links
Creation 05.10.2023
Last edited 06.10.2023
To cite this reference