An analytical and geoarchaeological approach on earthen plaster of 2nd century BCE Karle caves of Western Deccan, India

This study documents a holistic approach, combining mineralogical, geochemical and textural data to characterize the decorative earthen plaster of the 2nd century BCE. Buddhist rock cut caves of Karle in Western India. The analytical examination was carried out by the use of a petrological microscope, Laser particle size analysis, thin section analysis, XRF (X Ray fluorescence), XRD (X Ray Diffraction), FTIR (Fourier Transform Infrared Spectroscopy), SEM (Scanning Electron Microscope) and Raman spectroscopy in addition to the monitoring of environmental parameters. The results indicate that the local clayey soil, which is abundantly available in the high rain fed western coastal areas, was utilized for the earliest earthen plaster works. The characteristics of the clay seem to have been modified by mixing calcite and an organic adhesive. Rounded sub-angular aggregates derived from disintegration of basaltic rock and rice husk were added to influence shrinkage properties of the plaster. In addition to a better understanding of the technology and composition of ancient India's early earthen plasterworks, scientific data from the analysis was used to plan the composition of restoration plaster.