Efficiency of applying ammonium oxalate for protection of monumental limestone by poultice, immersion and brushing methods

Abstract

Samples of cretaceous limestone have been treated with three application methods (poultice, immersion and brushing) using different concentrations of ammonium oxalate solution (AmOx) and varying treatment time in order to test the efficiency of surface and in-depth formation of a protective layer of calcium oxalate (CaOx). Synchrotron-based microanalytical techniques (SR-µXRD with 12.5 µm × 7.5 µm (H × V ) probe size, SR-µFTIR with 10 µm × 10 µm and 8 µm × 20 µm probe sizes) and laboratory µFTIR, XRD and SEM have been employed for analysis of the treated samples. Synchrotron-based techniques showed variations in the CaOx distribution along the surface on a micrometer scale. All treatments resulted in the

Micro‐Raman analysis on the combined use of ammonium oxalate and ammonium phosphate for the consolidation and protection of carbonate stone artifacts

“…These type of stones along with sandstones are indeed among the most vulnerable toward environmental factors and in particular toward acid rain and condensation phenomena, which are frequently encountered in urban environments. In particular, treatments based on the passivating/ protective action of ammonium oxalate ((NH 4 ) 2 C 2 O 4 , AmOx) and on the consolidating effect of di‐ammonium phosphate ((NH 4 ) 2 HPO 4 , DAP) have been proposed over the last two decades . These inorganic agents show similar hydrophilic properties as well as a high affinity for limestones.…”

Semi‐quantitative analysis of the formation of a calcium oxalate protective layer for monumental limestone using combined micro‐XRF and micro‐XRPD

“…AmOx has been applied by brushing, immersion or poultice methods. The different treatment methods are described elsewhere . After treatment with AmOx, the samples were cut in half to 5 × 2.5 × 3 cm 3 to allow for cross‐sectional measurement of the calcium oxalate layer.…”

“…The main AmOx impregnation method, utilized by the Opificio delle Pietre Dure in Florence, involves the exposure of the stone surface for a period of 24 to 36 h to a saturated AmOx solution (5%) by means of a cellulose poultice . A recent study by the authors compares the effectiveness of different methods for the application of AmOx to the stone surface as well as the influence of treatment time and AmOx concentration used.…”

“…The scope of this paper is limited to the semi‐quantitative analysis route used for the comparison of different methods for the application of AmOx to calcite stone surfaces. The actual comparison of the different treatment methods as well as the influence of the treatment time and AmOx concentration used are discussed elsewhere …”

Ananalytical Study of Marble Consolidation by Oxalate Precipitation Using Density, Ftir and Powder-XRD Measurements

“…In the present study, typically 14220 interferograms were collected covering a spectral range from 4000 to 800 cm -1 at a resolution of 4 cm -1 with standard KBr beam splitter. Interferometer: Rock Solid, Permanent aligned, high stability, Scan Speed 3 velocities, 2.2 -20 kHz [8][9][10][11]. Also an analysis was made with X-Ray Powder Diffraction evidenced the presence of whewellite crystallites deposited on top of calcite.…”