Sending a clear message to graffiti artists

Historic buildings and monuments could be spared from graffiti damage, following the development of a long-lasting, transparent nanoparticle paint coating that can be used on any surface without altering its texture or appearance.

Current anti-graffiti paints must be reapplied regularly and often form a thick layer that can alter the appearance of buildings made from materials such as sandstone.Deletum 3000, developed by the Universidad Nacional Autonoma de Mexico in Santiago de Queretaro in central Mexico, consists of a water-based paint that is applied to a surface to create a layer with oil and water-repellent molecules on its surface.

The coating is claimed to work continuously for five years, even with regular cleaning, though its developers say it may last for up to twice this long. Dust and dirt also find it hard to stick to the coating’s surface, making it maintenance free.

When the coated wall is sprayed with a graffiti artist’s aerosol paint, it refuses to stick and runs. Only a very small residue of paint adheres to the wall, and this can be washed clean easily using a pressure hose.

The coating can also repel substances such as permanent marker, Professor Victor Castano, director of the university’s centre of Applied Physics and Advanced Technology, told the Institute of Nanotechnology’s ‘Nanotechnology in Crime Prevention and Detection’ conference in London last week. ‘Los Angeles spends £100m a year cleaning up graffiti. Even in London, the figure is around £8m. It is also a growing problem,’ he said.

The paint consists of inorganic nanoparticles of silicon oxide with a polymer attached to them in the shape of tiny balls, with a 15-20 nanometres diameter, evenly distributed throughout the substance.

It is designed so that the oil and water-repellent molecules rise to the surface upondrying, while the nanoparticles remain distributed throughout the film.

The resulting coating has a high ceramic content, making it extremely scratch resistant, and it can be applied to concrete surfaces, walls, all types of buildings and even cars, wood and metallic structures.

It is 97% transparent, though coloured versions are available, and is applied to cleaned surfaces by spray methods, brushes or rollers and can be used on previously-painted surfaces.

The product is designed to ensure that all the chemical components are totally stable, producing a substance that can last for months without changing its properties.

It therefore has a very high resistance to chemicals such as commercial and industrial solvents and to UV degradation, and can be applied in salty areas. It is also suitable for use in temperatures from -7 degrees C up to 70 degrees C.