La conservazione dei dipinti murali su intonaci in terra cruda: valutazione dell’ efficacia di materiali naturali tradizionali per il consolidamento corticale

The research aims at analysing some topics regarding the conservation of painted earth surfaces (wall paintings - pictorial layers) using natural substances. The emphasis was laid on the consolidation on archaeological earth surfaces. Two of the main materials traditionally used in the conservation of earthen architecture were experimented: the mucilage of Opuntia Ficus Indica and starch of rice. The research was carried out in situ as well as in the laboratory. The case study of Templio Pintado in the Archaeological sanctuary of Pachacamac (south of Lima, Peru coast) was analysed to comprehend the knowledge of the artefact and the methodologies used in the conservation. The selected materials were tested on some points of the pictorial surfaces of the Templio and the improvement of the cohesion was evaluated. In the laboratory, the effect of these materials on specially-made support was tested. These supports were created and accelerated aging following the knowledge learnt in the situ experience. The natural materials used in the consolidation were compared to the ethyl silicate; one of the synthesis products mainly used in the consolidation of this kind of pictorial support. Diagnostics investigation (OM, XRD, Colorimetric analysis) allowed evaluating the effects of the materials on the surface, completing the observation made in situ. The alternation between in situ and in laboratory experimentation was essential because it allowed to completely understand the problem being faced in the conservation and what are the real requirements for conserving these important, but vulnerable, surfaces. Keywords: wall paintings; plaster; Opuntia Ficus Indica mucilage; rice starch; surface consolidation; earthen architecture.