Analysis of potential direct insolation as a degradation factor of cave paintings in Villar del Humo, Cuenca, Central Spain

Abstract

The purpose of this study is to assess the impact of direct sunlight on eleven given points of interest in Villar del Humo (Cuenca, Central Spain), and to determine to what extent this direct insolation, which is affected by both the regional and the local geomorphological configuration, influences the state and type of degradation of the paintings or of the host rock. The analysis of potential direct insolation with geographical information system (GIS) tools and morphometric field measurements shows that in latitudes such as the ones studied in this case, not only insolation time but also the maximum angle of solar elevation above the horizon seem to be of relevance when it comes to determining the influence of direct insolation. We believe this to be useful information, in particular with regard to the management and preservation of this archaeological heritage, declared a UNESCO World Heritage Site.

Lightfastness assessment of Levantine rock art by means of microfading spectrometry

“…In addition, the moisture conditions and the geological features are some of the local factors that can cause an increase in deterioration. 5,6 Furthermore, Díez-Herrero et al 7 have demonstrated that sunlight can have adverse effects on these types of paintings due to thermal and photochemical degradation. Thermal deterioration is caused by the nonuniform distribution of temperature between the rock's surface and the core, causing fissures or damage in the rock.…”

Documenting the light sensitivity of Spanish Levantine rock art paintings

“…haematite, limonite, clay minerals, and charcoal) are not very light sensitive. However, some authors have demonstrated that exposure to sunlight can have adverse effects on these systems due to thermal and photochemical degradation of the historic materials (Díez-Herrero et al, 2009). It has been determined that thermal deterioration is mostly observed in the host rock and is caused by the non-uniform distribution of temperature at the core of the material.…”

Light penetration into Clarens sandstone and implications for deterioration of San rock art

“…In particular, it is planned to undertake some experiments (following Hall, 2004;Hall et al, 2005;Díez-Herrero et al, 2009) to study the impact of sunlight on exposed sandstone surfaces of different angles and aspects to better get an idea of the resulting changes in albedo and light-to-heat transfers. Finally, it is hoped to test a number of recent advances in chemical-based approaches to rock stabilization and surface protection (notably against graffiti; e.g., Fundazioa, 2009) in both the field and the laboratory.…”

“…A complication to all of this is the albedo of the rock and its components (see Hall, Guglielmin, & Strini, 2008b, for a discussion), as albedo is not constant but varies daily with the angle of the sun to the receiving surface (Oke, 1999) and changes through the year with the seasons. As Díez-Herrero et al (2009) have clearly demonstrated, solar insolation is a significant factor in causing the degradation of rock art, but its monitoring and evaluation are both complex and difficult.…”