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, 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.
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.
The Church of Santa Maria di Nazareth is famous for its marble facade, which has intricate details and sculptures. However, in July 2013 a sage leaf element suddenly fell from it, prompting a project to restore the facade.
The research team, led by scientists at China’s Northwestern Polytechnical University in Xian and the CNR-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.
They discovered the combination of two commonly used consolidation products – nanosilica and tetraethoxysilane (TEOS) – had the highest consolidating effect among all tested materials.
Nanosilica, as one of the most important nano materials, refers to silica particles with an average particle size ranging from 1 nanometre (nm) to about 100nm. It is widely used to conserve cultural heritage materials, such as outdoor building stones.
In the study published in the peer-reviewed journal Science China Technological Sciences in May, 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.
Their method, which was granted a patent, was adopted and applied by the church’s restoration project, according to the authors.
Cao Yijian, lead author of the study and a researcher with the Northwestern Polytechnical University’s institute of culture and heritage, said their approach had wide applications, including for stones similar to the project, such as stone tablets.
“Another reason for its wide potential application is that the two raw materials are very low cost and easy to buy in the market,” Cao said.
Carrara marble, a type of white or white-grey marble widely used in sculpture and building materials, was used to build the church’s facade.
The authors said that since the Ancient Roman period, Carrara marble had commonly been used as a building material for royalty and nobility in Europe.
The Church of Santa Maria di Nazareth was built in the late 17th century by a religious order called the Discalced Carmelites. It is also called the Church of the Scalzi (meaning barefoot in Italian).
But the stone was badly weathered by the high temperature differences between day and night in Venice, as well as high humidity and strong sea winds, according to the authors.
Venice is particularly vulnerable to climate change because the floating city is built atop around 120 islands and connected by more than 170 canals. The rising sea levels caused by global warming are expected to increase the frequency and intensity of flooding in the city.
The United Nation’s cultural agency Unesco last month recommended putting Venice on its World Heritage in Danger list as the city risked “irreversible” damage because of a string of issues including climate change and mass tourism.
Cooperation between China and Italy to restore and conserve cultural heritage dates as far back as the 1980s.
Cao said that cooperation would not be affected by Italy’s intention to quit China’s Belt and Road Initiative.
Italian Defence Minister Guido Crosetto said in July that Italy had an issue “to walk back [from belt and road involvement] without damaging relations” with Beijing.
Cao said: “I personally think Italy withdrawing from the [belt and road] may not be a short-term thing, but that will not affect the future in-depth cooperation between our two countries in the field of heritage restoration”.