The Ellora Caves in Mumbai Harbour are a magnificent complex of rock-cut caves with artwork dating back to 1000 CE, but the formations have stood the test of time. Archaeologists have wondered why they were in such good condition. Was it a special kind of rock that served as the foundation? Were there ancient principles of architecture?
A study was conducted to determine what gave the Ellora caves their durability and strength. The answer lies in a mixture of hemp with clay and lime plaster. This simple mix has preserved the 1,500-year-old caves from being degraded.
The team used various methods to arrive at this conclusion, including scanning using the electron microscope, Fourier transform, infrared spectroscopy and stereo-microscopic studies. In order to determine if the building blocks did indeed contain hemp, cannabis samples were collected from Jalna in Aurangabad and Delhi and matched with one of the Ellora caves. It was a perfect match!
“In the sample collected from the Ellora cave, we found a 10 percent share of cannabis sativa in the mix of mud or clay plaster. This is the reason why no insect activity is found at Ellora,” the study noted. At Ajanta, the neighboring caves, there have been signs of insect activity and degradation.
The cannabis fiber appears to have a better quality and durability than other fibers. Moreover, the cannabis’ gum and sticky properties might have helped clay and lime to form a firm binder. The hemp plaster has the ability to store heat, is fire-resistant and absorbs about 90 percent of airborne sound, creating a peaceful living environment for the monks at Ellora Caves.
While hemp and marijuana, the psychoactive drug, belong to the same plant species, they differ based in their THC content, which is the levels of the psychoactive component. Marijuana contains much higher levels than hemp.
The advantages of using hemp as a building material has been explored in England and Canada, where hempcrete (a mixture of hemp hurd and lime) is especially attractive because of its sustainable attributes. Hemp is superior to wood since it absorbs CO2 much more quickly.
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