Mineralogical and Spectroscopic Characterization of Some Products Resulting from the Weathering Process on the Tomb of Nakht-Djehuty (TT189), Western Thebes, Upper Egypt

The present study deals with the mineralogical and spectroscopic characterization of some weathering products formed on the decorated surfaces of the tomb of Nakht-Djehuty (TT189), during the time of Ramesses II (the 19th Dynasty, c.1279-1213 BC), western Thebes, Upper Egypt. The wall paintings in the ancient tombs of western Thebes are subjected to salt weathering as a result of the geological structure of the Theban formation and the environmental conditions of the region which enhance the formation of several forms of damage. The weathering forms observed are mainly flakes, salt efflorescence, biofilms and hard crusts. Damaged layers have been collected and investigated using scanning electron microscopy equipped with energy dispersive X-ray analysis system (SEM-EDS), Powder X-ray diffraction analysis (PXRD) and Fourier transform spectroscopy (FTIR). The results showed that the main dominant salts affecting the site are sodium chloride (halite, NaCl) and phases of sulphates [gypsum, CaSO4 · 2H2O; bassanite, CaSO4 · 0.5H2O and anhydrite, CaSO4] were also detected. FTIR spectra collected on a KBr pellet of thin dark layers covering the decorated surfaces indicated the detection of calcium oxalate probably derived from biodegradation of the organic binders in tempera techniques or the organic coatings used in old restorations of the murals