New approaches in stone protection – comfort, material preservation, and energy saving in one!

Long-term hygiene as the flagship of the “City by the River”

To permanently protect their new sandstone benches along the Neckar promenade from dirt, bird droppings, chewing gum, graffiti, and the growth of algae and moss, the city of Heidelberg has coated the stone surfaces with the environmentally friendly high-performance coating from Nanopool. The invisible multifunctional layer against dirt adhesion and weather residues ensures that natural impurities on the surfaces are washed away by rain alone. This makes the recreational area by the riverside even more attractive and, at the same time, saves water, supporting energy-saving measures – the so-called energy retrofit.

Moisture and moss cushions can form an extremely thin biofilm on stone surfaces, which permanently damages the substrate and delays the drying of the stones. The professional NP® coating prevents this and thus increases both material protection and the comfort factor. In doing so, the treated surface is neither visually nor tactually altered.

High quality: Natural stone remains breathable

Unlike many common conventional stone impregnations, the NP® coating gives natural stone its new repellent properties without sealing it airtight: The layer is so ultra-thin that it wraps around the individual grains, thus not closing pores and joints.

As a result, the stone dries quickly and without restriction when moisture enters from the underside. This was also confirmed in an official report by the Institut für Steinkonservierung e. V. (Institute for stone conservation): In collaboration with Dr. Tombers & Partner – Gesellschaft für Bauschadensforschung, Materialprüfung und Umweltanalytik mbH (Society for building damage research, material testing, and environmental analysis), the determination of the water vapor diffusion resistance factor µ for the Nanopool product was conducted. The results showed that despite the high protective effect of the multi-performance layer, the permeability to water vapor in the treated sandstone sample corresponds to that of an untreated stone.

Protection against driving rain and frost-thaw cycles

Natural stone, in particular, can be severely damaged over time by weather conditions. Among other things, the capillary action of driving rain leads to the saturation of the stone, causing not only mold and algae growth but also gradually triggering the disintegration of the substrate through frost-thaw cycles.

The NP® protective coating prevents this by preventing moisture from penetrating the stone, eliminating the source of any material changes.


The Institut für Steinkonservierung e. V. (Institute for stone conservation) determined, among other things:

  • Investigations on different stone samples show that the water-repellent effect of NP®Stone Protect is long-lasting and does not impair the drying of the stone when moisture enters from the back.

  • No changes in the stone surface have been observed on a sample that has been exposed for several years. Untreated and conventionally treated stone samples with hydrophobic agents show some microbial growth, while the samples treated with the (NP®) spray do not.

  • The effectiveness of the NP® product was demonstrated even after 100 test cycles in the frost-thaw and frost-thaw-salt exposure tests.

  • The adhesion of moss and the formation of algae are prevented without the use of biocidal additives.