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Nanomaterial restoration of colossal statues on Mount Nemrut (Türkiye)

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[downloaded from https://whc.unesco.org/en/list/448]

Before getting to the nanomaterial restoration, here’s a little information about the project, Nemrut Dağ, from its UNESCO (United Nations Educational, Scientific and Cultural Organization) World Heritage List webpage,

Nemrut Dağ

The mausoleum of Antiochus I (69–34 B.C.), who reigned over Commagene, a kingdom founded north of Syria and the Euphrates after the breakup of Alexander’s empire, is one of the most ambitious constructions of the Hellenistic period. The syncretism of its pantheon, and the lineage of its kings, which can be traced back through two sets of legends, Greek and Persian [emphasis mine], is evidence of the dual origin of this kingdom’s culture.

Description is available under license CC-BY-SA IGO 3.0

Outstanding Universal Value

Brief synthesis

Crowning one of the highest peaks of the Eastern Taurus mountain range in south-east Turkey, Nemrut Dağ is the Hierotheseion (temple-tomb and house of the gods) built by the late Hellenistic King Antiochos I of Commagene (69-34 B.C.) as a monument to himself.

With a diameter of 145 m, the 50 m high funerary mound of stone chips is surrounded on three sides by terraces to the east, west and north directions. Two separate antique processional routes radiate from the east and west terraces. Five giant seated limestone statues, identified by their inscriptions as deities, face outwards from the tumulus on the upper level of the east and west terraces. These are flanked by a pair of guardian animal statues – a lion and eagle – at each end. The heads of the statues have fallen off to the lower level, which accommodates two rows of sandstone stelae, mounted on pedestals with an altar in front of each stele. One row carries relief sculptures of Antiochos’ paternal Persian ancestors, the other of his maternal Macedonian ancestors. Inscriptions on the backs of the stelae record the genealogical links. A square altar platform is located at the east side of the east terrace. On the west terrace there is an additional row of stelae representing the particular significance of Nemrut, the handshake scenes (dexiosis) showing Antiochos shaking hands with a deity and the stele with a lion horoscope, believed to be indicating the construction date of the cult area. The north terrace is long, narrow and rectangular in shape, and hosts a series of sandstone pedestals. The stelae lying near the pedestals on the north terrace have no reliefs or inscriptions.

The Hierotheseion of Antiochos I is one of the most ambitious constructions of the Hellenistic period. Its complex design and colossal scale combined to create a project unequalled in the ancient world. A highly developed technology was used to build the colossal statues and orthostats (stelae), the equal of which has not been found anywhere else for this period. The syncretism of its pantheon and the lineage of its kings, which can be traced back through two sets of legends, Greek and Persian, is evidence of the dual origin of this kingdom’s culture.

Criterion (i): The tomb of Antiochos I of Commagene is a unique artistic achievement. The landscaping of the natural site of Nemrut Dağ is one of the most colossal undertakings of the Hellenistic period (some of the stone blocks used weigh up to nine tons).

Criterion (iii): The tomb or the Hierotheseion of Nemrut Dağ bears unique testimony to the civilization of the kingdom of Commagene. Antiochos I is represented in this monument as a descendant of Darius by his father Mithridates, and a descendant of Alexander by his mother Laodice. This semi-legendary ancestry translates in genealogical terms the ambition of a dynasty that sought to remain independent of the powers of both the East and the West.

Criterion (iv): More so than the tombs at Karakus and Eski Kahta, the tumulus at Nemrut Dağ illustrates, through the liberal syncretism of a very original pantheon, a significant, historical period. The assimilation of Zeus with Oromasdes (the Iranian god Ahuramazda), and Heracles with Artagnes (the Iranian god Verathragna) finds its artistic equivalent in an intimate mixture of Greek, Persian and Anatolian aesthetics in the statuary and the bas-reliefs.

Integrity

Nemrut Dağ is largely intact and truthfully and credibly expresses it Outstanding Universal Value. The important cult areas of Commagene still exist, the structures are the original ones and their original interrelations can still be observed and perceived.  Although the property boundary contains the tumulus and the east, west and north terraces, it does not include the full extent of the ceremonial routes. The greatest threat to the integrity of the property is the material damage caused by environmental conditions such as serious seasonal and daily temperature variations, freezing and thawing cycles, wind, snow accumulation, and sun exposure.  The height of the tumulus is now reduced from its estimated original 60 m due to weathering, previous uncontrolled research investigations and climbing by visitors. Furthermore, the Nemrut property is located within a first degree earthquake zone and is very close to the East Anatolian Fault, which is seismically active. Therefore, the tumulus, statues and stelae are vulnerable to earthquakes.

Authenticity

Nemrut Dağ retains its authenticity in terms of form, materials and design as one of the unique artistic achievements of the Hellenistic period with its fascinating beauty of monumental sculptures in a spectacular setting. It has survived  in a moderately well-preserved state. The original ceremonial routes to the Hierotheseion are known and still used for access today.

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I highlighted ‘syncretism’ and ‘Greek and Persian legends’ in the previous excerpt as I found a different description which includes another influence while confirming the debt to Greek and Persian legends in this September 12, 2021 article for Arthipo,

Nemrut Mountain Statues, Kingdom of Commagene and Mount of Gods

Nemrut Mountain Statues is an archeological site that is among the archaeological hits of Asia Minor, and at the same time still keeps many secrets. Until now, it has not been possible to pinpoint what the artificial embankment at the top of the mountain hides. The colossal statues on Mount Nemrut are an excellent example of religious syncretism and Antiochus’ attempt to introduce a new state cult combining Greek, Persian and Armenian influences [emphasis mine].

Mount Nemrut Sculptures History and Art

Crowning one of the highest peaks of the Eastern Taurus mountain range in southeast Turkey, Mount Nemrut is the Hierotheseion (temple-tomb and home of the gods), built by the late Hellenistic King Antiochos I of Commagene (69-34 BC). The mausoleum of Antiochus I (69-34 BC), who ruled on Commagene, a kingdom established in the north of Syria and the Euphrates after the collapse of Alexander’s empire, is one of the most ambitious structures of the Hellenistic period. The syncretism of its pantheon and the lineage of its kings, which can be traced through two series of legends, Greek and Persian [emphasis mine], is evidence of the dual origin of the culture of this kingdom.

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Material Used

The monuments on Nemrut Mountain Statues were built using two main types of rock materials; the first was a gray-green rock called tufite, consisting of a pyroclastic material containing a significant mixture of sedimentary material. These include steles with pictures of ancestors on the two main terraces, several small sculptures and minor architectural elements. The other material was the much more durable white and yellow limestone rock, which was also the main building material and from which huge statues and altars were carved.

Preservation and nanotechnology in Türkiye

The Nemrut Dağ preservation project is described in two different articles. There is significant overlap but also new detail in each one. This July 19, 2025 article by David Ramirez for The Anatoolian provides good detail,

The monumental statues atop Mount Nemrut, a UNESCO World Heritage Site, are undergoing advanced conservation efforts using nano lime technology. Initiated in 2022, the restoration work has yielded promising results, leading to the expansion of the project in 2025.

Located at an altitude of 2,206 meters, Mount Nemrut hosts colossal stone sculptures that have endured centuries of harsh environmental conditions. To address the micro-cracks forming on their surfaces and internal structures, experts began applying nano-dispersed calcium hydroxide solutions. Following successful trials, the project now focuses on the iconic Eagle Head and King Antiochus I statues on the western terrace.

A Blend of Technology and Preservation

In the initial phase, layers of dirt and grime are meticulously removed from the statue surfaces. Then, the nano lime solution is carefully injected into the cracks using syringes. This not only strengthens the stone from within but also prevents water infiltration caused by rain and atmospheric conditions.

The method is designed to maintain the natural appearance of the stones, allowing visitors to experience the statues in their original form. The restoration phase is expected to take approximately one month, focusing on sustainable conservation without compromising historical authenticity.

Expanded Restoration in 2025

Ayşe Ebru Çorbacı, Director of the , stated that a test application on the Heracles statue in 2022 had shown effective results:

“After observing the success of the pilot project, we planned a comprehensive restoration for 2025. Our goal is to strengthen the structural integrity while preserving the aesthetic features of the statues. The cracks won’t be completely filled, allowing the original forms to remain visible.”

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An August 22, 2025 article for Türkiye Today adds more information,

Authorities in Türkiye have begun a large-scale preservation project for the colossal statues on Mount Nemrut using nanotechnology.

The effort aims to protect the two-thousand-year-old stone heads from further erosion caused by wind, snow, and sun.

Nanotechnology methods strengthen Nemrut statues against erosion

The Ministry of Culture and Tourism announced that the first stage of the project was completed between July 7 and 27 [2025].

A team of one expert from Adiyaman Museum and six restorers worked on the eastern and western terraces of the mountain. They focused on the heads of King Antiochos and the eagle, two sandstone reliefs, and the head of Apollo.

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“With the first consolidation works, the heads of Antiochos, the eagle, and the statue of Apollo have regained their integrity. Thanks to the interventions made with nanotechnology on the east and west terraces, the texture of the stones was strengthened and cracks were closed.” [Culture and Tourism Minister Mehmet Nuri Ersoy]

Restoration team uses new tech to protect Nemrut’s monuments

The team used different nanomaterials depending on the stone.

Limestone monuments were cleaned mechanically and biologically, then reinforced with a nano-particle calcium hydroxide solution. Cracks were filled with a hydraulic lime-based mortar. Sandstone works were treated with nano-dispersed ethyl silicate to block water from seeping into the stone.

One of the most symbolic results was on the Apollo statue. Its headpiece, which had been reattached and separated several times in the past, was permanently fixed during this round of work.

Minister Ersoy emphasized that this was the first time such methods were permanently applied at Nemrut. “Nano lime and nano silicate techniques have breathed new life into Nemrut’s stones for the first time,” he said.

Five year conservation roadmap aims to secure Nemrut’s future

The project is planned to continue over five years. Test studies began in 2022 and monitoring continued through 2023 and 2024 before this summer’s application phase. …

There’s more about stone here in a November 10, 2023 posting “Preserving stone and repairing historic Church of the Scalzi in Venice (Italy) with nanotechnology.” The nanotechnology solution mentioned in the Italian story is in fact a nanosilica solution similar to the one being used at Nemrut Dağ. There are the other stone stories mentioned in the 2023 piece,

My other stone postings:

Preserving stone and repairing historic Church of the Scalzi in Venice (Italy) with nanotechnology

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Since stone wears* down and away with time these researchers from China and Italy are trying to find ways to mitigate the damage. (At the end of this piece I have a list of other posts about stone buildings and monuments, preservation, and nanotechnology.)

From an August 23, 2023 news snippet by Echo Xie for the South China Morning Post, Note: Links have been removed,

A team of Chinese and Italian researchers has restored parts of a 300-year-old Catholic church in Venice, Italy, using modern nanotechnology.

The Church of Santa Maria di Nazareth [Church of the Scalzi], which overlooks the Grand Canal and is a prime example of Venetian Baroque architecture, is the beneficiary of a patented method developed to consolidate, or treat, marble stones damaged by time and the elements.The research was funded by the Veneto regional government, the National Natural Science Foundation of China, and the Ministry of Science and Technology’s belt and road foreign expert exchange programme [part of the Belt and Road Initiative?].

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There’s a more extended Sept. 6, 2023 snippet about the research on Vuink,

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The cutting-edge method could be used to restore landmarks of world-class cultural heritage – including the Pantheon, Trajan’s Column and the Victoria Memorial in London as well as historic sculptures – made from marble similar to the church [Church of Santa Maria di Nazareth]

The research team, led by scientists at China’s Northwestern Polytechnical University in Xian and the CNR [National Research Council of Italy]-Institute of Geosciences and Earth Resources in Florence, Italy, found an “effective and enduring” method to consolidate marble stones after the design and systematic study of nine different treatment methods.

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Ivana Milanovic’s, ASME [American Society of Mechanical Engineers] Fellow’s Post [undated] on LinkedIn provides more details,

… They [research team] discovered the combination of two commonly used consolidation products – nanosilica and tetraethoxysilane (TEOS) – had the highest consolidating effect among all tested materials.

In the study published in the peer-reviewed journal [Science China Technological Sciences], the authors used a two-step method to consolidate the marble stones. They first applied nanosilica with dimensions less than 10nm to the surface of the stone using a poultice, a paste-like material, to cover the stone. The nanosilica particles could then penetrate as deep as 5cm (2 inches) into the pores of the stone and consolidate it. Then they used the same poultice method and put TEOS on the surface, which could enhance the stone’s hardness or mechanical strength. …

Here’s a link to and a citation for the paper,

Enhanced consolidation efficacy and durability of highly porous calcareous building stones enabled by nanosilica-based treatments by YiJian Cao, Mara Camaiti, Monica Endrizzi, Giorgio Forti, Ernesta Vergani & Ilaria Forti. Science China Technological Sciences volume 66, pages 2197–2212 (2023 Published May 18, 2023

This paper is behind a paywall. However, it is possible to request a PDF copy of the paper from the authors on their Research Gate “Enhanced consolidation efficacy and durability of highly porous calcareous building stones enabled by nanosilica-based treatments” webpage,

My other stone postings:

That should be enough, eh?

*’stone’ changed to ‘stones’ on November 4, 2025.

Europe’s cathedrals get a ‘lift’ with nanoparticles

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That headline is a teensy bit laboured but I couldn’t resist the levels of wordplay available to me. They’re working on a cathedral close to the leaning Tower of Pisa in this video about the latest in stone preservation in Europe.

*ETA August 7, 2019: Video reinserted today.*

I have covered the topic of preserving stone monuments before (most recently in my Oct. 21, 2014 posting). The action in this field seems to be taking place mostly in Europe, specifically Italy, although other countries are also quite involved.

Finally, getting to the European Commission’s latest stone monument preservation project, Nano-Cathedral, a Sept. 26, 2017 news item on Nanowerk announces the latest developments,

Just a few meters from Pisa’s famous Leaning Tower, restorers are defying scorching temperatures to bring back shine to the city’s Cathedral.

Ordinary restoration techniques like laser are being used on much of the stonework that dates back to the 11th century. But a brand new technique is also being used: a new material made of innovative nanoparticles. The aim is to consolidate the inner structure of the stones. It’s being applied mainly on marble.

A March 7, 2017 item on the Euro News website, which originated the Nanowerk news item, provides more detail,

“Marble has very low porosity, which means we have to use nanometric particles in order to go deep inside the stone, to ensure that the treatment is both efficient while still allowing the stone to breathe,” explains Roberto Cela, civil engineer at Opera Della Primaziale Pisana.

The material developed by the European research team includes calcium carbonate, which is a mix of calcium oxide, water and carbon dioxide.

The nano-particles penetrate the stone cementing its decaying structure.

“It is important that these particles have the same chemical nature as the stones that are being treated, so that the physical and mechanical processes that occur over time don’t lead to the break-up of the stones,” says Dario Paolucci, chemist at the University of Pisa.

Vienna’s St Stephen’s is another of the five cathedrals where the new restoration materials are being tested.

The first challenge for researchers is to determine the mechanical characteristics of the cathedral’s stones. Since there are few original samples to work on, they had to figure out a way of “ageing” samples of stones of similar nature to those originally used.

“We tried different things: we tried freeze storage, we tried salts and acids, and we decided to go for thermal ageing,” explains Matea Ban, material scientist at the University of Technology in Vienna. “So what happens is that we heat the stone at certain temperatures. Minerals inside then expand in certain directions, and when they expand they build up stresses to neighbouring minerals and then they crack, and we need those cracks in order to consolidate them.”

Consolidating materials were then applied on a variety of limestones, sandstones and marble – a selection of the different types of stones that were used to build cathedrals around Europe.

What researchers are looking for are very specific properties.

“First of all, the consolidating material has to be well absorbed by the stone,” says petrologist Johannes Weber of the University of Applied Arts in Vienna. “Then, as it evaporates, it has to settle properly within the stone structure. It should not shrink too much. All materials shrink when drying, including consolidating materials. They should adhere to the particles of the stone but shouldn’t completely obstruct its pores.”

Further tests are underway in cathedrals across Europe in the hope of better protecting our invaluable cultural heritage.

There’s a bit more detail about Nano-Cathedral on the Opera della Primaziale Pisana (O₽A) website (from their Nano-Cathedral project page),

With the meeting of June 3 this year the Nano Cathedral project kicked off, supported by the European Union within the nanotechnology field applied to Horizon 2020 cultural heritage with a fund of about 6.5 million euro.

A total of six monumental buildings will be for three years under the eyes and hands of petrographers, geologists, chemists and restorers of the institutes belonging to the Consortium: five cathedrals have been selected to represent the cultural diversity within Europe from the perspective of developing shared values and transnational identity, and a contemporary monumental building entirely clad in Carrara marble, the Opera House of Oslo.

Purpose: the testing of nanomaterials for the conservation of marble and the outer surfaces of our ‘cathedrals’.
The field of investigation to check degradation, testing new consolidating and protective products is the Cathedral of Pisa together with the Cathedrals of Cologne, Vienna, Ghent and Vitoria.
For the selection of case studies we have crosschecked requirements for their historical and architectural value but also for the different types of construction materials – marble, limestone and sandstone – as well as the relocation of six monumental buildings according to European climates.

The Cathedral of Pisa is the most southern, fully positioned in Mediterranean climate, therefore subject to degradation and very different from those which the weather conditions of the Scandinavian peninsula recorded; all the intermediate climate phases are modulated through Ghent, Vitoria, Cologne and Vienna.

At the conclusion of the three-year project, once the analysis in situ and in the laboratory are completed and all the experiments are tested on each different identified portion in each monumental building, an intervention protocol will be defined in detail in order to identify the mineralogical and petrographic characteristics of stone materials and of their degradation, the assessment of the causes and mechanisms of associated alteration, including interactions with factors of environmental pollution. Then we will be able to identify the most appropriate method of restoration and testing of nanotechnology products for the consolidation and protection of different stone materials.

In 2018 we hope to have new materials to protect and safeguard the ‘skin’ of our historic buildings and monuments for a long time.

Back to my headline and the second piece of wordplay, ‘lift’ as in ‘skin lift’ in that last sentence.

I realize this is a bit off topic but it’s worth taking a look at ORA’s home page,

Gabriele D’Annunzio effectively condenses the wonder and admiration that catch whoever visits the Duomo Square of Pisa.

The Opera della Primaziale Pisana (O₽A) is a non-profit organisation which was established in order to oversee the first works for the construction of the monuments in the Piazza del Duomo, subject to its own charter which includes the protection, promotion and enhancement of its heritage, in order to pass the religious and artistic meaning onto future generations.

«L’Ardea roteò nel cielo di Cristo, sul prato dei Miracoli.»
Gabriele d’Annunzio in Forse che sì forse che no (1910)

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If you go to the home page, you can buy tickets to visit the monuments surrounding the square and there are other notices including one for a competition (it’s too late to apply but the details are interesting) to construct four stained glass windows for the Pisa cathedral.

Historic and other buildings get protection from pollution?

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This Sept. 15, 2017 news item on Nanowerk announces a new product for protecting buildings from pollution,

The organic pollution decomposing properties of titanium dioxide (TiO2 ) have been known for about half a century. However, practical applications have been few and hard to develop, but now a Greek paint producer claims to have found a solution

A Sept. 11, 2017 Youris (European Research Media Center) press release by Koen Mortelmans which originated the news item expands on the theme,

The photocatalytic properties of anatase, one of the three naturally occurring forms of titanium dioxide, were discovered in Japan in the late 1960s. Under the influence of the UV-radiation in sunlight, it can decompose organic pollutants such as bacteria, fungi and nicotine, and some inorganic materials into carbon dioxide. The catalytic effect is caused by the nanostructure of its crystals.

Applied outdoors, this affordable and widely available material could represent an efficient self-cleaning solution for buildings. This is due to the chemical reaction, which leaves a residue on building façades, a residue then washed away when it rains. Applying it to monuments in urban areas may save our cultural heritage, which is threatened by pollutants.

However, “photocatalytic paints and additives have long been a challenge for the coating industry, because the catalytic action affects the durability of resin binders and oxidizes the paint components,” explains Ioannis Arabatzis, founder and managing director of NanoPhos, based in the Greek town of Lavrio, in one of the countries home to some of the most important monuments of human history. The Greek company is testing a paint called Kirei, inspired by a Japanese word meaning both clean and beautiful.

According to Arabatzis, it’s an innovative product because it combines the self-cleaning action of photocatalytic nanoparticles and the reflective properties of cool wall paints. “When applied on exterior surfaces this paint can reflect more than 94% of the incident InfraRed radiation (IR), saving energy and reducing costs for heating and cooling”, he says. “The reflection values are enhanced by the self-cleaning ability. Compared to conventional paints, they remain unchanged for longer.”

The development of Kirei has been included in the European project BRESAER (BREakthrough Solutions for Adaptable Envelopes in building Refurbishment) which is studying a sustainable and adaptable “envelope system” to renovate buildings. The new paint was tested and subjected to quality controls following ISO standard procedures at the company’s own facilities and in other independent laboratories. “The lab results from testing in artificial, accelerated weathering conditions are reliable,” Arabatzis claims. “There was no sign of discolouration, chalking, cracking or any other paint defect during 2,000 hours of exposure to the simulated environmental conditions. We expect the coating’s service lifetime to be at least ten years.”

Many studies are being conducted to exploit the properties of titanium dioxide. Jan Duyzer, researcher at the Netherlands Organisation for Applied Scientific Research (TNO) in Utrecht, focused on depollution: “There is no doubt about the ability of anatase to decrease the levels of nitrogen oxides in the air. But in real situations, there are many differences in pollution, wind, light, and temperature. We were commissioned by the Dutch government specifically to find a way to take nitrogen oxides out of the air on roads and in traffic tunnels. We used anatase coated panels. Our results were disappointing, so the government decided to discontinue the research. Furthermore, we still don’t know what caused the difference between lab and life. Our best current hypothesis is that the total surface of the coated panels is very small compared to the large volumes of polluted air passing over them,” he tells youris.com.

Experimental deployment of titanium dioxide panels on an acoustic wall along a Dutch highway – Courtesy of Netherlands Organisation for Applied Scientific Research (TNO)

“In laboratory conditions the air is blown over the photocatalytic surface with a certain degree of turbulence. This results in the NOx-particles and the photocatalytic material coming into full contact with one another,” says engineer Anne Beeldens, visiting professor at KU Leuven, Belgium. Her experience with photocatalytic TiO2 is also limited to nitrogen dioxide (NOx) pollution.

“In real applications, the air stream at the contact surface becomes laminar. This results in a lower velocity of the air at the surface and a lower depollution rate. Additionally, not all the air will be in contact with the photocatalytic surfaces. To ensure a good working application, the photocatalytic material needs to be positioned so that all the air is in contact with the surface and flows over it in a turbulent manner. This would allow as much of the NOx as possible to be in contact with photocatalytic material. In view of this, a good working application could lead to a reduction of 5 to 10 percent of NOx in the air, which is significant compared to other measures to reduce pollutants.”

The depollution capacity of TiO2 is undisputed, but most applications and tests have only involved specific kinds of substances. More research and measurements are required if we are to benefit more from the precious features of this material.

I think the most recent piece here on protecting buildings, i.e., the historic type, from pollution is an Oct. 21, 2014 posting: Heart of stone.