A multi-analytical approach for the study of red stains on heritage marble

Abstract

Red stains are a common discolouration on stone cultural heritage all over the world.

Weathering mechanism of red discolorations on Limestone object: a case study from Lingyan Temple, Jinan, Shandong Province, China

“…Studies carried out by micro-Raman spectroscopy showed the presence of minium (Pb 3 O 4 ), which confirmed the inorganic substance [8]. Subsequently, a series of research shows that red discoloration critically depends on the environment bacteria, decorate pigment, and human intervention [9]. The chromatic alteration process includes three parts: (a) enzymatic decolorization of bacterial pigments [10], (b) atmospheric attack of lead building components [11], and (c) production of hematite through washing and leaching of alkaline silicates [12].…”

The San Giovanni Baptistery in Florence (Italy): Assessment of the State of Conservation of Surfaces and Characterization of Stone Materials

“…In the Table 2 the mineralogical, petrographic, and isotopic features of white and veined marbles are reported. Previous research, consisting of a multi-analytical approach for the study of the presence of red discouloration on the white marble of the external cladding of the Bapstistery, pointed out that the red staining is due to the presence of minium (lead tetraoxide) concentrated prevalently in the calcite crystal boundaries [26].…”

“…All mortar samples suffered a strong recrystallization of the binder in the form of spathic calcite. In different depths of S5, some differences in the aggregate characteristics were present: S5 (7-12) cm was composed of abundant binder/aggregate (B/A 1/3) and fine grain size predominant, while S5 (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26) cm and S5 (26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38) cm were characterized by less binder/aggregate (B/A 1/2-1/3), and a fine-medium size was predominant (Figure 9e). Furthermore, a different amount of carbonate rock fragment was registered, with respect to the attic mortar samples (a higher entity in S5 samples).…”

“…The TGA analyzes were performed on representative samples: the selection was based on petrographic observations. The samples from attic: S1 (10-15) cm, S2 (9-14) cm, S3 (0-4) cm, S4 (4-20) cm; from the women's gallery: S5 (7-12) cm, S5 (12-26) cm, S5 (26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38) cm; and from the basement S8 (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38) cm, S12 (0-4) cm, S14 (0-4) cm, and S16 (4-12) cm were analyzed. The variation of hydraulic behavior in the depth were evaluated in samples collected from the women's gallery (S5).…”

“…This is the case of the sample in Figure7, where the Raman analysis shows the presence of a yellow brownish pigment, yellow ochre (iron oxides and hydroxides), calcite (1086 cm −1 ), gypsum (1007 cm −1 ), and calcium sulphate (1019 cm −1 ). The results suggest that the yellow patina is linked to a previous maintenance intervention of color toning of the window frame: in fact, it is assumed that it has been given a coating with lime water and yellow ochre.Previous research, consisting of a multi-analytical approach for the study of the presence of red discouloration on the white marble of the external cladding of the Bapstistery, pointed out that the red staining is due to the presence of minium (lead tetraoxide) concentrated prevalently in the calcite crystal boundaries[26].…”