Monument conservators at the Otto Friedrich University in Bamberg have developed a new imaging method that can be used to determine the condition of natural stone non-invasively. Advertorial Article Parallax Article
Monument conservators at the Otto Friedrich University in Bamberg have developed a new imaging method that can be used to determine the condition of natural stone non-invasively.
As part of the interdisciplinary and international “Nano-Cathedral” project, Prof. Dr. Rainer Drewello from the Chair of Restoration Science in the Conservation of Historic Buildings examined the condition of the stone in the cathedrals of Cologne, Pisa, Ghent, Vitoria-Gasteiz and Vienna as well as the ten-year-old opera house in Oslo between 2015 and 2018.
The aim of the EU project, which was funded with 6.3 million euros, was to develop tailored solutions for the conservation of natural stone at nano level in order to ensure the preservation of cultural heritage in Europe. The scientists developed manufacturing agents that stabilize the stone at depth and hydrophobic agents to seal the materials.
The “opto-technical monitoring” developed by Drewello and his colleague Max Rahrig was the documentation basis for the development and quality control of the nanoparticles. These are 1000 times thinner than the diameter of a human hair, which is why sophisticated technology is required to visualize the particles and their effect. The imaging process combines four techniques to provide an all-round view of the condition of the original rock before and after treatment with the nanomaterials.
High-resolution 3D images measure the rock surface with an accuracy of 0.3 millimetres and VIS color photography highlights color differences on the surfaces. UV fluorescence photography and infrared photography make foreign materials such as preservative coatings or the growth of bacteria, lichens or mosses visible. The advantage over previous analysis methods is that, on the one hand, monument conservators can analyze the rock without destroying it or touching it and, on the other hand, opto-technical monitoring can be used over a large area and can examine two square meters of test surface in one operation.
This is a breakthrough in monument conservation, as Rainer Drewello explains: “Imaging methods are already used in monument conservation, but until now there was hardly any way of testing new materials for the conservation of rock without destroying at least parts of the rock by taking samples.”
The research team from six European countries was initially able to measure the original condition of the rocks in the cathedrals and the opera house and, after a year, document weak points and progressive weathering. Both the newly developed preparations and the imaging process have a promising future: in order to monitor the long-term protective function of the newly developed materials, the researchers will carry out further measurements in two, five and eight years’ time. This will enable them to document the deterioration of the rock and bring the nanomaterials to market maturity. The Dombauhütten have expressed an interest in continuing the investigations and are to be enabled to carry out measurements themselves in a further step.
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