Evaluation of the reliability and durability of some chemical treatments proposed for consolidation of so called-marble decoration used in 19th century cemetery (Hosh Al Basha), Cairo, Egypt.

   The conservation of so called-marble ornaments is a very important cultural heritage issue, since this kind of decoration was widely use for casing stone buildings during 19^th and beginning of 20^th centuries in Egypt. The wide variation of materials and techniques used for imitating natural marble is a really big challenge for conservators. Actually most of so called- marble decorations are subjected to several degradation agents which can lead to the loss of material cohesion mostly caused by alteration phenomena that often produce the detachment of large areas of imitated marble ornaments. Surface consolidation, directed to achieve cohesion and stability, is based on the use of materials with aggregating properties. This study started with characterization of the yellow veined imitated marble stucco used in Hosh Al Basha courtyard dating back to Mohammed Ali's family period (1805-1952) in Egypt. The imitated marble stucco consists of two main layers. The outer finishing layer, yellow paint veined with brown color, composed mainly of yellow zincite (ZnO). Gypsum (CaSO₄.2H₂O), halite (NaCl) and calcite (CaCo₃) were detected in this layer also. The mineral composition of the subsurface layer (prime layer) shows the presence of gypsum (major mineral), zincite (ZnO), anhydrite (CaSO₄) and halite (NaCl) were also detected.  Two products (Paraloid B-72 and SILRES® BS OH 100) were selected to evaluate their efficiency for consolidation treatments of imitated marble stucco. The selected products were tested under thermal ageing. Polarizing microscope (PLM), scanning electron microscopy with the energy dispersive X-ray (SEM-EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR-ATR) and colorimetric measurements were used in performing the study.