ANALYTICAL STUDY OF RENDERS AND PIGMENTS FROM THE CLASSICAL TEMPLE OF ZEUS AT NEMEA, GREECE

• I. Doganis, A. Galanos (Archaeological conservators)
• P. Theoulakis (Department of Conservation of Antiquities and Works of Art, T.E.I. of Athens, Ag. Spyridonos str., 122 10 Egaleo, Greece)
• I. Karatasios, V. Kilikoglou (Laboratory of Archaeometry, Institute of Material Science, N.S.C.R. "Demokritos", 153 10 Aghia Paraskevi, Attikis, Greece)

This study concerns the characterisation of renders and pigments, used on the stone surfaces of the temple of Zeus, at Nemea both for protective and decorative purposes. Samples were taken from several architectural members. The render has been exceptionally well preserved, its thickness does not exceed 2 mm and it is particularly even and homogeneous, with good adherence to the substrate; it was observed that pigments were applied both on the render and on the stone surfaces.

Since ancient times, the development of mortar technology has been closely related to improvements in the quality of raw materials and to the transfer of knowledge from other regions. As a result, a wide range of mortars and renders are encountered through the ages, depending on monument type, use, historic period and region.

Although mortars appear to be a common and simple material, they are very complicated multi-phase systems. Ancient mortars with similar mineral and chemical composition do not necessarily have the same microstructure, physical properties or durability. Thus, the study of mortars technology helps to extract archaeological, historical and architectural data.

Examination of samples under the polarising and scanning electron microscope revealed the existence of two distinct layers, with different binder to aggregate ratio and variable aggregate size. Mineralogical analysis of the mortar using X-ray diffractometry indicated that slaked lime and pure calcite aggregates from high quality crushed white marble and crystalline limestone were used.

The chemical and mineralogical analysis of two different pigments, red and blue, was carried out using X-ray diffractometry, energy dispersive X-ray analysis, and Fourier transformed infrared spectroscopy. The thickness of painting layer varies from 0,5mm to 0,2mm.

Biological growth observed under the external (preparatory painting layer) of render.

In order to investigate the possible use of organic additives to the renders or organic binder into the pigment layer, representative samples were analysed using Fourier transformed infrared spectroscopy. Analytical results indicate the use of pretentious media. Furthermore, the high concentration of phosphorus into the render matrix could be attributed to the use of animal glue or to the presence of bone powder as additive to the binder.