Nanogel used to clean damaging patinas from artefacts

Materials World magazine
2 Nov 2016

A new nano-gel developed by an Italian student is being used to remove damaging patinas from artefacts. Natalie Daniels reports.

Disappointed by the lack of products to remove biological patinas from artefacts, Irene Scarpa, CEO of NasierTech, Italy, has developed Nasier Gel, a non-toxic product making use of nanomaterials and enzymes. 

Exposure to the weather can often lead to the growth of lichens and black or green patinas on statues and stone façades. Toxic products, such as biocides and pesticides, are often used to remove biological patinas. However, these are unselective and can eat into the surface of the monuments. After developing a solution to remove microorganisms on surfaces during her time at Ca’ Foscari University of Venice, Italy, Scarpa went on to form a university spin-off company, NasierTech. 

Explaining the process, Scarpa commented, ‘Nasier Gel is non-toxic for the operator and the environment. It is selective and cannot react with the elements, because of the presence of the enzymes.

‘The gel attacks the patina, not the surface of the work. Nanostructured compounds have far-reaching potential. The nanometric dimensions of the particles increases the contact surface with the patina needing to be removed.’ 

Finding the right combination

Scarpa saw the potential of nanoparticles to optimise the use of enzymes. ‘Previously, it was very difficult to use enzymes because of their need to be monitored – they need specific pH levels and temperatures to be active. They are also not as stable because they cause autolysis – the self-destruction of a cell or tissue by a self-producing enzymes,’ she said. The nanoparticles stabilise the enzymes, preventing autolysis, and the need to control the pH and temperature – these can be regulated from the gel and conserved for months. The Nasier Gel is directly applied to a surface or via an interface and takes around 30 minutes after application to stone artefacts and between three-to-five minutes for paintings, textiles, wood and paper.

During experiments at the university, Scarpa and an interdisciplinary team in the Department of Molecular Sciences and Nanosystems were able to reduce the production costs of the nano-structured composite by €500 to €180 per kilo. Final tests on lichens showed the gel had taken away all of the impurities on a cement statue and degraded the biological patina within 20 minutes. The product is more expensive than conventional methods, but with reduced application time and a simple to use method, Scarpa aims to make the gel available for everyone, not just chemists.

‘With other methods of removal, a biological patina requires lengthy and repeated treatment to get satisfactory results. Using our gel, you need only one or two applications to remove the patina from the surface and the application can be finished in a few minutes,’ Scarpa claims. The technology, which has been patented, is currently being used to restore stone monuments, paintings, icons and frescoes. 

The company now plans to develop the product on an industrial scale, ‘I think that we can develop this kind of treatment further, studying a way to protect and consolidate the monument after Nasier Gel is applied and also further the potential of the product, so stay tuned.'