Phosphate treatments for stone conservation: 3-year field study in the Royal Palace of Versailles (France)

Abstract

Phosphate treatments for conservation of stone have provided so far encouraging results in laboratory studies, as they exhibit good effectiveness, compatibility and durability to accelerated weathering tests. However, limited data are available about their long-term performance in real environment. Here, a systematic evaluation of phosphate consolidants after prolonged exposure in the field is reported for the first time. Naturally weathered marble specimens and a XVII century marble sculpture located in the Park of the Royal Palace in Versailles were treated by various formulations of the phosphate consolidant. Their conservation state was assessed before treatment by non-destructive methods (ultrasounds, color measurement, water absorption) and, in the case of the specimens, also by slightly destructive tests (SEM, FT-IR, MIP, IC). The conservation state of the specimens and the sculpture was further assessed right after treatment and then periodically monitored during exposure in the Versailles Park. Characterization after field exposure demonstrated that some formulations of the phosphate treatment are able to slow down marble deterioration, although it was not completely inhibited. Limited alterations in water absorption and aesthetic appearance confirmed the general compatibility of the phosphate treatment.

Advances in the application of nanomaterials for natural stone conservation

“…Once applied on weathered stones onsite, good consolidation results were obtained in the treatments of a marble gravestone [54], a marble byzantine sarcophagus [55], and a Hellenistic-Roman tomb in marlstone from Cyprus [56]. Promising results were also obtained from a 3-year monitoring program of naturally weathered marble specimens and a 17 th century marble sculpture from the Park of the Royal Palace in Versailles (France), proving that some of the phosphate-based materials were able to hinder marble deterioration [57].…”

Using Maxwell’s Theory to model and quantify the fracture evolution of cyclothymic deposition phosphate rock

“…(a) The slip and diffusion resistance to mineral crystals have a close relationship with the lattice constant and its spatial structure (Li, 2009;Wang et al, 2015;Sassoni et al, 2021). It was pointed out in the literature that dolomite crystals belong to the trigonal system and its molecular formula is CaMg [CO 3 ] 2 and a 0 = 0.601 nm.…”

Advanced mapping of inorganic treatments on porous carbonate stones by combined synchrotron radiation high lateral μXRPD and μXRF

“…Since the mid-1990s, various inorganic treatments have been developed to restore microstructural cohesion within damaged stones matrixes 2 – 4 . In such context, ammonium oxalate (AmOx) and di-ammonium phosphate (DAP) solutions have gained prominence for carbonate stones in the past two decades 5 – 7 . These water-soluble salts react with the carbonate matrix of the stone substrate to produce micrometric reaction products (ranging from 0.1 to 4 µm in crystal size) 8 .…”