Material characteristics and deterioration problems of roman mosaics in Antandros ancient city

Abstract

In Roman period, fascinating, colorful and highly detailed mosaics were formed by laying small colored stones, pieces of marble, ceramics and glass tesserae on setting bed. Their conservation requires knowledge concerning the construction techniques, properties of the used materials as well as the problems of deterioration. In this study material characteristics and deterioration problems of Roman mosaics found in a Roman Villa in Antandros Ancient city (Altınoluk, Balıkesir) have been determined in order to define the properties of the original mortars and tesserae, and the main characteristics of the intervention materials, which will be used in the conservation works of mosaics. For this purpose, basic physical properties, mineralogical, chemical and microstructural characteristics of preparatory mortars and tesserae were determined by color spectrometer, standard RILEM test methods, XRD, XRF, SEM-EDS and TGA analyses. Results indicated that mosaics had a multilayered system composed of tesserae, bedding layer, nucleus and rudus from the surface to bottom. Tesserae were small cubes of stone, ceramic and opaque glasses. Stone tesserae were limestones and dolomites. Ceramic tesserae were produce from different raw clay sources by heating them at high temperatures. Glass tesserae were natron based and classified as soda-lime, lead, and soda-lime lead glasses. They were opacified with Ca and Pb-antimonates typical of Roman period and colored with transition metals. The thin bedding layer in which the tesserae were embedded was non-hydraulic lime mortar. Nucleus and rudus mortar layers were composed of crushed brick aggregates and lime. Brick aggregates were pozzolanic and binders of mortar layers were hydraulic due to pozzolanic brick aggregates. The binders exhibited a uniform structure and the strong adherence between brick aggregates and lime. Deterioration processes of the mosaics in Antandros Ancient city caused by destroyed original drainage systems, settlement in the mosaic floors, changes in temperature and humidity and biological colonization. Based on the results of this study, the recommendations are developed for the conservation works of the mosaics.