Ammonium Phosphate for “Green” Conservation of Cultural Heritage: 10 Years of Research in the Laboratory and in the Field

This paper presents a summary of results obtained in the last 10 years on the use of ammonium phosphate solutions for conservation of heritage stones and mortars.After a brief introduction about the genesis of this treatment, the most used formulations are presented. Various functionalities of the treatment are reviewed, then its compatibility and durability are discussed. Recent results on the treatment environmental sustainability are also reported. The treatment’s performance in comparison with alternative consolidants (ethyl silicate, nanolimes, acrylic resin) is then evaluated and, finally, some pilot applications of ammonium phosphate onto real buildings and monuments are reviewed. All the laboratory and field studies published so far point out ammonium phosphate as one of the most promising inorganic treatments currently available for conservation of heritage materials.