Characterization of 6–11th century A.D decorative lime plasters of rock cut caves of Ellora

• The traditional base for paint is a combination of several mud/lime plaster layers.
• The stratigraphy of consecutive layers (techniques) differs.
• Fine/medium grained siliceous aggregates were mixed in feebly dolomitic aerial lime for plaster.
• Identification of Cannabis sativa indicates knowledge of hempcrete technology to ancient indians.

The historic decorative lime plasters of Ellora caves, dated back to 6–11th century A.D have been investigated for their mineralogical, micro-structure and chemical characterization. The analytical studies were performed by means of optical microscopy, XRF, laser particle size analyzer, FTIR, XRD, Raman Spectroscopy, Scanning Electron Microscope and thermal analyzer. Traditional lime plaster is applied in 2–3 layers above the host rock but interestingly the techniques differ at India’s Ellora cave. From the analytical data it appears that all the lime plaster is composed of mixture of feebly dolomitic lime binder (aerial lime) mixed with fine to medium grained siliceous aggregates with addition of Cannabis sativa (Canabeacease) as an organic filler. The finding indicates that hempcrete technology was known to the ancient Indians in 6th century A.D and probably this is the first authentic report about the use of cannabis as filler in ancient lime plaster.