Originally, two campaigns of emergency conservation work were necessary: the first in 1988 and the second in 1991. After that, a conservation project on the whole site was considered. Its main objective would be the long-term preservation of the paintings. Consequently, various investigations have been carried out to establish:
A) An accurate knowledge of the painting technique and therefore of its stability
- A study of the pigments found in the paintings to establish their light fastness and chemical stability. In fact, we believe that no degradation has occurred since the pigments were first applied.
- A study of the ground under the painting. This analysis showed that kaolin dug from the surrounding area was used, after being well sifted and sorted in order to obtain a homogeneous substance free from large particles. The analysis also established the water absorption properties of the kaolin.
- A study of the binding media. Establishing the nature of the binding media was a main objective from the outset. The analysis showed that the material binding the pigments and the ground (kaolin) was an animal fat (butter made from cow's milk). This explains why the paintings survived such humid conditions so well.
- Finally, a mineralogical classification of the slabs of the dolmen. This study allowed us to identify the quarry from which these stones came. It also provided some information about the low capillary absorption of the stones.
B) Various potential deteriorating agents that may affect long term preservation
- A study of microclimatic conditions inside the dolmen. Relative humidity and temperature, both inside and outside the dolmen, were recorded throughout one year. In this way, we have defined the current environment as well as potentially damaging factors. For example, measurements of the rock surface temperature indicate that the dew-point is reached often, which explains why the paintings remain wet most of the time.
- A study of biodeterioration inside the dolmen. The concentration of algae, fungi and lichens is reasonably low. Therefore it can be assumed that, under current conditions, biodeterioration can be considered a secondary degradation factor.
- High relative humidity measurements inside the dolmen led us to propose a local hydrogeology study. Results of this study confirm that the phreatic surface may fluctuate close to the ground level, to the point where it sporadically reaches the base of the paintings.
Complementary tasks including soil analyses, colorimetry, structural stability, and so on.
Data collected during the above investigations have allowed us to define potentially damaging factors and to propose control actions. These include:
- Building a protective shelter above the dolmen.
- Installing systems for phreatic level monitoring and drainage, so as to avoid excessive wetness of the paintings.
- Installing a microclimate measurement station to monitor the effect of these actions.
- Possibly, installing a climate control station (relative humidity, temperature, air circulation, etc.) to ensure that climatic parameters remain stable.
It is planned that the work on the dolmen of Dombate will start in summer 1996.
Copyright © 1996, J.M. Bello, F. Carrera, F. Cebrián, Last Updated - 16/09/96 17:49:34