Investigation of degradation mechanisms by portable Raman spectroscopy and thermodynamic speciation: The wall painting of Santa María de Lemoniz (Basque Country, North of Spain)

On the stability of mediaeval inorganic pigments: a literature review of the effect of climate, material selection, biological activity, analysis and conservation treatments

“…Copper basic sulphates (CuSO 4 ·yCu(OH) 2 ·zH 2 O: brochantite, langite, posnjakite, antlerite) are formed according to pH, humidity and temperature [119,127,129]. Copper chlorides and sulphates can further react to form other salts [127].…”

“…Acidic conditions are commonly found in, and surrounding, polychrome objects, as a result of biological activity on the object [53] or of degradation of the organic binders (e.g. oxalic acid [129,135]). Diluted acids decompose malachite (for example acetic, hydrochloric, nitric acid [126]), causing the release of Cu 2+ ions, and the formation of the most stable phase according to pH and other present ions.…”

On the Use of the Unusual Green Pigment Brochantite (Cu4(SO4)(OH)6) in the 16th-Century Portuguese-Flemish Paintings Attributed to The Master Frei Carlos Workshop

“…In the literature a few examples of the presence of brochantite in green pigment in mural paintings, usually interpreted as a natural mineral associated to malachite in copper ores (Bersani et al, 2003) or as the result of malachite degradation are mentioned (Pérez-Alonso et al, 2006;Castro et al, 2008). Although this pigment was not frequently identified, its use was also reported in illuminations from the 14th century in Europe (Gilbert et al, 2003) and 16th-century Italian oil paintings on copper (Pitarch et al, 2011).…”

“…There are several related minerals, such as dolerophanite Cu 2 O(SO 4 ), antlerite Cu 3 (SO 4 )(OH) 4 , posnjakite Cu 4 (SO 4 )(OH) 6 (H 2 O), langite Cu 4 (SO 4 )(OH) 6 2(H 2 O), and wroewulfite Cu 4 (SO 4 )(OH) 6 2(H 2 O) (Frost, 2003;Martens et al, 2003;Pérez-Alonso et al, 2006) that show similar Raman bands. Therefore, μ-XRD was applied to characterize crystalline phases in the pigment layer (Fig.…”

Raman spectroscopic analysis of a belltower commemorative wall decoration

“…From the identification of mineral pigment composition, degradation and substrates in ancient frescoes and wall paintings [6][7][8][9][10] and in polychrome statuary [11] to the discovery and evaluation of biological degradation in organic dyes [12,13], textiles [14,15], endangered rock art exposed to hostile environments [16][17][18][19][20] and on the pigments on historiated manuscripts and parchments [21][22][23][24][25][26][27][28][29][30][31][32][33][34] much novel information has been revealed at both a microscopic and macroscopic level of molecular interrogation. In particular, for manuscript pigment analysis and characterisation, a combination of Raman spectroscopic and other microanalytical techniques is found to be extremely useful.…”