Mortar samples from historic masonries dated from Hellenistic to Ottoman period were examined using stable isotope analysis. The study focuses on the analysis of stable isotopes of oxygen and carbon (¹³C and ¹⁸O), to determine the origin of calcite and to diagnose the state of preservation of historic mortars.Samples of mortars were collected from historic constructions and wall-paintings dating from Hellenistic to Ottoman period. The main aims of this research programme are to investigate the technological transition of historic mortars from Hellenistic to Ottoman period and to examine the potential sources of material degradation. To achieve the aims of the project the samples will be analysed using traditional techniques of instrumental analysis such as X-ray diffraction and scanning electron microscopy with X-ray microanalysis. Parallel to this, stable isotope analysis (¹³C and ¹⁸O) will be performed in order to obtain further knowledge on the technology, provenance and degradation of historic mortars. The signs of material decay are expected to be reported in isotopic values and therefore determine the sources of mortar’s degradation. Moreover it has been developed a calibration model based on stable isotope of carbon (¹³C) and radiocarbon (¹⁴C) analysis for dating culture heritage material of mortars. The experience of response of ancient and historic mortars under radiocarbon and stable isotopes interpretation, resulted in development of construction materials for restoration projects in order to assess the degradation of historical buildings due to environmental impact (air pollution, acid rain, salinity, microbiological process).