Painting technique and state of conservation of wall paintings at Qusair Amra, Amman Jordan

The state of conservation of the frescoes at Qusayr Amra was investigated by integrated physico-chemical measurements, particularly optical and scanning electron microscopy, m-infrared spectroscopy, mass spectrometry and X-ray powder diffraction. The frescoes appear darkened and severely damaged owing to the deterioration of surface treatments and to the widespread presence of different salts. These caused significant detachments of the painting layers. The materials used in the painting and preparation layers and in the wall plaster were characterized in order to clarify the painting technique. Different pigments have been identified on the pictorial layers: the original ones corresponding to green earth, yellow and red ochre, realgar, bone black and lapis lazuli and those ascribing to recent restoration works, such as titanium white and cobalt blue. Proteinaceous materials (egg or yolk) have been identified as binder for the pigments, indicating a tempera painting technique. Three different products belonging to restoration interventions have been also identified: the natural product shellac ascribable to next-to-last restoration and scarcely removed during last restoration also because of its insolubility, the synthetic vinyl acetate and acrylic polymers. Particularly the latter one indicates an on-going degradation of the applied fixatives. The extensive deterioration of the surfaces is also due to the widespread presence of salts, such as chloride, nitrate and sulphate clearly identified by XRD measurements. The obtained results give a comprehensive overview on the employed painting technique and its state of preservation and on the causes of the painting deterioration. Therefore, they are a fundamental tool to develop durable and compatible materials and methodologies for a future conservation strategy of this site.