Ammonium phosphates to consolidate carbonatic stone mate- rials: an inorganic-mineral treatment greatly promising

reasons. There is fi rst an undoubted responsibility of the scientifi c community and of the conservator restorers that have traditionally dealt with the problem without a suffi ciently critical and deep approach, opting in most cases for the easiest and/or more immediate solutions, rather than privileging the more durable and reliable over long time. But there is, also, an objective great diffi culty to fi nd solutions that really meet the delicate task. The complexity lies in different aspects of the problem: the compatibility of the treatments with the stone matrix of the objects; the optical-chromatic alterations frequently induced by the treatments both immediately and, especially, over time; the actual possibility, in the case of consolidation, to interest homogeneously and effectively a suffi cient depth within the treated material; the ability to retreat the object, at a distance of time, without incurring in the problem of accumulating the consolidating or protecting agent. Instead, in the light of the numerous experiences conducted in the recent decades, seems no longer a problem the condition of reversibility: this, for intrinsic reasons of the treatment, in the case of consolidation, and by the very nature of the materials that have to respond to other requirements, in the case of protection. Following what said above, any new, more aware and more in-depth attention to the problem of the consolidation and protection of stone artifacts is therefore welcome. The consolidating products, employed in the conservation fi eld, can be divided in two classes: the fi rst one includes the organic-polymeric products; generally it deals with products marketed in solution of suitable organic solvents, whose consolidating effect of the stone material occurs upon of the evaporation of the solvent [Vicini, 2001,143; Wheeler, 2005]. The second class includes inorganic-mineral products; in this case the consolidating effect is the consequence of different chemical processes (hydrolysis, chemical interaction with the stone substrate etc.) which produce the crystallization of new mineralogical phases [Hansen, 2003, 13]. It is the authors’ belief that the research of new more appropriate products for the consolidation and protection of stone monuments should be developed, primarily, in the mineral-inorganic fi eld. It is for sure a more diffi cult fi eld than the organic-polymeric one, but it offers the advantage of being based on materials theoretically more compatible with the substrate and more durable than those of the other area which at a minor extent can guarantee the reliability at long times requested from restoration.