Low-cost non-toxic coating to preserve marble

A team of researchers from Princeton University in the United States has developed a low-cost and non-toxic treatment to help preserve iconic stone structures from decay. The treatment involves the application of a thin film of a calcium compound called hydroxyapatite, which is formed by the reaction of a water-based phosphate salt solution and calcite, the mineral that makes up marble. The solution seeps into and binds cracks in the marble’s surface, creating a stronger building or monument that is also more resistant to environmental pollution and rain.

The study not only discovered that hydroxyapatite has excellent sticking properties, but also that their method has the advantage of being based on a non-toxic solvent (water), being able to penetrate deep inside marble cracks, and reacting in just 24 hours.

The team conducted preliminary tests using hydroxyapatite at the Certosa di Bologna in Italy; the researchers believe the new treatment developed at Princeton could help preserve artworks in the cemetery from the effects of time and weather.

Further tests will now look at the possibility of improving the hydroxyapatite treatment by eletrodeposition. They are also planning to start a pilot application of the hydroxyapatite treatment on some sculptures in the park of the Palace of Versailles in France. A single application of the treatment is said to have the potential to protect a marble structure for decades.