Maria Stephanidou leans towards the microscope. What he studies is like a rock. But in fact, this is a precious fragment of Byzantine masonry, discovered during excavations of the metro station in Venizelu. On the computer screen, this century-old work is enlarged, revealing the first secrets of its composition.

This “examination” is the first step in the study of each monumental material entering the Building Materials Laboratory of the Aristotelian University of Thessaloniki. From the benches of the laboratory, located on the ground floor of the Polytechnic School, passed samples from some of the most important monuments of all Greece: from the Rotunda and the ancient finds of the metro stations of Agia Sophia and Venizelos to the ancient theater of Thassos, but also newer ones, such as the mansions of Western Macedonia.

The laboratory studies the materials of these monuments, fixes the damage done to them by time and the climate crisis, and at the same time offers compatible materials for their restoration.

As Ms. Stephanidou, Director of the Laboratory and Professor of the Department of Civil Engineering at AUTH, explained, the laboratory has had this research direction in the study of material monuments and historical buildings for the past thirty years. “We have examined a large number of monuments throughout Greece, and this methodology has also been applied to monuments abroad,” he notes in an interview with K.

The data that scientists have collected over time is also a great asset, as they can now make comparisons between different years and see how the monuments have been affected by the climate crisis, which is now an important risk factor for the country’s cultural property. as well as other aggravating circumstances.

A series of studies proves how the climate crisis is damaging monuments not only in Greece, but throughout the Eastern Mediterranean. Ms. Stephanidou argues that climate change is related to the frequency and intensity of certain events, such as floods. So, she explains, when a material is subjected to more frequent wetting and drying cycles that cause corrosion, its fabric softens more easily, its strength decreases, the way the materials are joined changes, so it can be attacked. static monument. “The impression of wear can be a simple change in color. However, it can also be more serious, on a larger scale, such as creating cracks in the material, loosening, loss of strength and, finally, loss of the material itself,” he notes.

They are looking for suitable materials to weld the fragments brought from the Venizelos metro station.

An important project in which he will be involved is the movement of ancient finds to the metro station in Venizelos. “Whenever they need or bring material for repositioning, we will be able to use compatible materials to weld the transported fragments,” she emphasizes.

The restoration material created by the researchers does not imitate the original monument, but has some similar characteristics. These new materials undergo various tests to determine their durability. The researcher showed us how she tests the strength of a material by placing a cube made from it under a press that applies loads to it. Within minutes, under pressure, the seemingly indestructible material began to crack and then disintegrate. The researcher calmly observed the test and then noted the corresponding values.

In another area of ​​the laboratory there are also special artificial aging chambers, where new materials are subjected to freeze and thaw cycles, intensified by the climate crisis, in a salt fog that mimics the conditions experienced by monuments located on the coast, as well as in acid rain, to determining the rate at which they can wear out.

As Ms. Stephanidou describes, the secret of the previous ones, which usually combined lime with pozzolana, i.e. volcanic earth, was the good quality of the raw materials. “Whatever plan we make, whatever recipe we give, it will not succeed if there are no good raw materials.” For this reason, the laboratory tries and, despite the omnipotence of the cement that has taken over the production, has identified and collaborates with specific local lime producers who continue to produce quality lime from Ioannina to Crete. When it comes to volcanic land, Greece is lucky to be on islands like Milos, Skyros and Kimolos.

As the professor used to say, materials are magical, and when combined with science and craftsmanship, they can work wonders.

I hold in my hands the work of the ancient masters

The AUTH building materials laboratory detects all changes and damages with specialized equipment. Students are active in almost every step of this study. Their every movement, from determining the color of a fragment of a monument to processing it in chemistry, is slow and careful, exuding the respect with which they hold these unique objects in their hands. “We are excited. I have been doing this research for 30 years and I hold in my hands materials that have been made by craftsmen, artisans, restorers for centuries. And this is shocking every time, because every time you learn something new,” emphasizes the director of the workshop.

First, the laboratory receives a sample of a monument or building, which is obtained with the help of archaeologists and restorers. After examining it under a microscope, the researchers painstakingly break the sample in a mortar and grind it into granules, the size of which is measured. After that, the remaining “powder” is delivered to a chemist, where it is analyzed through a series of procedures. The extracted result is recorded on the tab of each monument.

The recording helps prevent investigators from intervening when necessary when wear or damage is minor, so that in the event of an earthquake or severe weather event, more serious problems will not arise, which will be more expensive to repair. It is for this purpose that the laboratory cooperates with various antique institutions throughout the country.

Irini Tsardaka, a PhD student at the Department of Civil Engineering, has gone through all the steps of the above process and is now focusing on chemistry, where she does the analysis. To get to the laboratory, he passes through the Castles every day. “What I see is not dead to me. Building materials of monuments are alive. It’s like having five children, and both are more sensitive and need more care,” she explains. Ms. Tsardaka conducts a thorough and consistent chemical analysis every time to know exactly what material was used by those who built them. This research helps, he says, to give “sensitive children” a suitable little brother: a compatible restorative material that will allow damaged monuments to continue to live. It is also one of the most creative processes undertaken by laboratory scientists.

“Someone put craftsmanship, art into every monument, and it came to you after so many centuries, and now you are called to do something similar. The responsibility is huge. Our task is to pass on to the next generations what we have received, and, perhaps, to continue the amazing story: the construction technologies of Greece,” concludes Ms. Stephanidou.