It takes seconds to spray on graffiti, but hours or weeks to remove – especially from porous natural stone or brickwork as found in the majority of historic monuments. The paint penetrates deep into the pores from which it is impossible to remove, even with a pressure hose or multi-component solvents.
Often the only answer, other than living with the graffiti, is to etch away a part of the wall. Special anti-graffiti polymer coatings have been on the market for several years.
They create a hydrophobic seal that closes the pores, preventing the paint from adhering to the undersurface and allowing it to be wiped off. But as a result the building can no longer breathe, augmenting the risk of mold development or salt efflorescence. Because they cannot be removed easily, such coatings also run counter to the principles of conservation, which require that any changes must be reversible.
“There are conflicting requirements for this kind of polymer coating – it mustn’t seal the pores, because it is important that there should be a continuous exchange of air between the building and the external environment, and at the same time it has to prevent the spray paint from penetrating the pores. The coating needs to be sufficiently resistant to withstand both weathering and mechanical cleaning. Moreover, since we’re dealing with historic landmarks, it must be possible to completely remove the coating from the walls if required, to restore them to their original condition with little effort and without damaging the structure,” says Professor André Laschewsky, who heads the relevant research group at the Fraunhofer Institute for Applied Polymer Research IAP in Potsdam.
As part of an EU-sponsored project, Laschewsky’s team and partners from the Center of Polymer and Carbon Materials of the Polish Academy of Sciences in Gliwice and Zabrze have developed a polymer coating that meets these requirements. “Our innovative polymer film seals the pores in the substrate, so that graffiti paint doesn’t penetrate. But its micro-porous structure also creates a hydrophobic barrier that allows water vapor to escape from the building while at the same time preventing the infiltration of rainwater,” says Laschewsky.
The coating can be removed from the surface using a diluted brine solution which modifies its chemical composition and allows it to be washed off. Coordinated by the LABEIN Foundation in Spain and the german Federal Institute for Materials Research and Testing the partners have coated samples of ancient stone and brick and repeatedly covered them with graffiti – which was removed completely each time.
Prof. Dr. Andre Laschewsky | Fraunhofer Gesellschaft
Physics, photosynthesis and solar cells
01.12.2016 | University of California - Riverside
New process produces hydrogen at much lower temperature
01.12.2016 | Waseda University
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy