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Lime, Clay & A Curious Third Ingredient: What Preserved the Ellora Caves for 1500 Years?

ASI member Rajdeo Singh and botany professor Milind M Sardesai found that cannabis was integral in helping preserve the ancient Ellora caves and preventing decay, paving way for new conversations around sustainable architecture.

Lime, Clay & A Curious Third Ingredient: What Preserved the Ellora Caves for 1500 Years?

From mud homes in the deserts of Rajasthan to houses made only with old beer bottles — sustainable homes are the talk of the town these days, and so the materials that can be in their construction are endless — bamboo, straw bales, recycled plastic, cork, upcycled wood, and rammed earth, to name a few. 

One material often left out of the conversation is cannabis. But that changes now. 

If you’ve ever had the chance to visit the Ellora Caves in the Mumbai Harbour — around 10 km east of the main city — you’d recall marveling at the magnificent complex of rock-cut caves with artwork dating back to 1000 CE, stepping into the cool, hearing the steady drip of water somewhere in the distance, and gaping at the fact that after all these decades, the formations have stood the test of time. 

The reason, as has now been found, is the cannabis in the architecture. 

An astounding find

Archaeology experts shared a sense of intrigue since time immemorial about the sheer existence of the UNESCO World Heritage Site the Ellora caves. How were they in such good condition? Was it a special kind of rock that served as the foundation? Were there ancient principles of architecture? 

The answer, as was revealed in a study in 2016, 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 16th Ellora Cave in the mighty complex
The 16th Ellora Cave in the mighty complex, Picture source: Twitter: Tourism of India

The duo behind this discovery were Rajdeo Singh, a former superintendent archaeological chemist of the Archaeological Survey of India’s science branch (western region), and Milind M Sardesai, who teaches botany at Dr Babasaheb Ambedkar Marathwada University. This study was conducted to determine what gave the Ellora caves their durability and strength. 

The study states, “The use of hemp helped the caves and most of the paintings remain intact at the 6th century Unesco World Heritage site. The caves are breathtaking examples of rock-cut architecture that stand testimony to the imagination and artistry of its creators.” 

The duo used various methods to arrive at this conclusion. These included 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. 

With these findings, it comes as no surprise that the set of 34 caves at Ellora, with their temples and monasteries, remain so well preserved, while at Ajanta, the neighbouring caves, there have been signs of insect activity and degradation. 

However, the duo were intrigued as to what specific properties of hemp made it such a versatile building material. 

Sardesai was quoted saying, “The cannabis fibre appears to have a better quality and durability than other fibres. Moreover, the cannabis’ gum and sticky properties might have helped clay and lime to form a firm binder. As the hemp plaster has the ability to store heat, is fire-resistant and absorbs about 90 percent of airborne sound, a peaceful living environment for the monks has been created at Ellora Caves.”

As the spotlight falls on conversations around how hemp can be used in construction, it also raises important questions about the use of hemp in modern society and the legalities associated with it. 

Cannabis and its tryst with society

While hemp and marijuana, the psychoactive drug, belong to the same plant species, they differ based on their THC content, which is the levels of the psychoactive component. 

Marijuana, which contains much higher levels than hemp, is banned under the Narcotic Drugs and Psychotropic Substances (NDPS) Act, meaning that anyone found growing, transporting or consuming the plant will face serious repercussions. 

The Ellora caves architecture have been preserved for over 1500 years
The Ellora caves architecture have been preserved for over 1500 years, Picture source: Twitter: Itishree

Uttarakhand was the first state in India to permit the commercial cultivation of industrial hemp. 

The laws in the country regulate the cultivation and sale of cannabis strictly. According to the current framework, if it is extracted from the leaves of the cannabis plant and does not contain more than 0.3 percent of THC (the psychoactive compound), then it is considered to be completely legal and can be sold. 

These products are recognised as hemp seed products and are a hero ingredient in the medical and nutritional industry for their many benefits. 

So, when it comes to the question of using hemp as a construction material, there are several unanswered questions. 

Speaking to The Times of India, Rajendra Mugdia, a special public prosecutor who had earlier in the capacity of additional public prosecutor tried over a dozen cases under the NDPS Act, 1985, said, “If hemp comes into use for construction work, it might lead to gross misuse. The government will have to make some amendments to the law introduced in 1985.  A separate authority will have to be created for allotting permissions.”

That said, the advantages of using hemp as a building material has been explored overseas, particularly in England. 

In The Hempcrete Book, authors William Stanwix and Alex Sparrow, who have been engaged in one such construction that employs hemp, say it is a wonderful material. The book cites that hempcrete is especially attractive to self-builders and community groups because of the relatively low-tech nature of the construction method. 

It adds, “Timber products can also claim to be sequestering carbon; however, hemp is superior to wood in this respect since it absorbs CO2 much more quickly, creating a very hard woody stem (2-4 m in height) in only 4-5 months.” 

Scientists Say That Cannabis Helped Preserve Ellora Caves From Decay For 1500 Years by Krupa Joseph, Published on 8 June 2021. 
Hemp shielding Ellora caves from decay for 1,500 years: Study by Syed Rizwanullah, Published on 10 March 2016.
What is hemp and is it legal in India? Know everything about it here by Financial Express, Published on 29 December 2022. 

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