Pigments used in Roman wall paintings in the Vesuvian area

Abstract

Powdered pigments found in bowls from the Pompeii archaeological site and some wall-painting fragments from the Vesuvian area (conserved in the National Archaeological Museum of Naples) were investigated by microscopic Raman and FTIR spectroscopies, X-ray diffraction and scanning electron microscopy-energy dispersive X-ray. Brown, red and yellow pigments are common ochres based on goethite and haematite. The blue pigment is Egyptian blue: the presence of tridymite and cristobalite indicates firing temperatures in the 1000-1100 • C range. Pink pigments were prepared both with purely inorganic materials, by mixing haematite and Egyptian blue (violet hue), or presumably by adding an organic dye to an aluminium-silica matrix. A white powder found in a bowl is composed mainly of the unusual pigment huntite (CaMg 3 (CO 3 ) 4 ). Celadonite is found in the green samples from the wall paintings, together with Egyptian blue and basic lead carbonate, while the heterogeneous green pigment in a bowl shows malachite mixed with goethite, Egyptian blue, haematite, carbon, cerussite and quartz.

Raman spectroscopy as a tool to diagnose the impact and conservation state of Pompeian second and fourth style wall paintings exposed to diverse environments (House of Marcus Lucretius)

“…4, all the measurements in which gypsum and other sulfate salts (i.e. mirabilite) appear (1)(2)(3)(4)(5)(6) are from within the first 30 µm of the face in direct contact with the atmosphere. In all those measurements gypsum was identified, but in the rest of the measurements performed deeper than 30 µm sulfates were not found.…”

“…Sulfates (SO 4 2− ) and other anions (F − , Cl − , NO 3 − and C 2 O 4 2− ) were considered for the quantification, apart from the soluble cations (Na + , NH 4 + , K + , Mg 2+ and Ca 2+ ). As the wall fragments W-1 and W-1 were detached from the same place, for the quantification of soluble salts, the external layer of both fragments (W-1 intonaco) and the inner parts of both fragments (W-1 arriccio) were respectively mixed.…”

“…Some Raman spectrum obtained after the point-by-point Raman analysis from the outer to the inner part of the mortar showing the massive superficial (more or less 10 µm) presence of gypsum(1)(2)(3)(4)(5)(6) and the absence of this salts in the inner parts(7)(8)(9).…”

Characterisation of the pigments in a Ptolemaic Egyptian Book of the Dead papyrus

“…A valuable white pigment was represented by huntite, a calcium magnesium carbonate [CaMg 3 (CO 3 ) 4 ] used almost exclusively for wall paintings from the Predynastic period (3900-3150 BC) up to the Late period (664-525 BC;Riederer 1987;Heywood 2001;Uda 2004;Scott et al 2009). This pigment has been identified in samples either alone or with chalk (CaCO 3 ) and gypsum (CaSO 4 ·2H 2 O; Shedid 1988) and occurs for instance also within Roman wall paintings in Italy ( Baraldi et al 2007) and pigments from Pompeii (Aliatis et al 2010). While huntite can be associated to dolomite [CaMg(CO 3 ) 2 ] and magnesite [Mg(CO 3 )] deposits located near Abu Rawash in the north-western Desert (Riederer 1987;Hühnerfuß et al 2006), calcium carbonate is more or less available in all over Egypt and gypsum in the upper part of the Nile river (Colombo 1995); besides the employment of eggshells and seashells supposed by Lucas (1962), an important source of marine sediments exploited during Roman times for obtaining the so-called paraetonium is located on the coast of the Libyan Desert (Colombo 1995;Pliny Hist Nat, XXXV, 36).…”

Raman spectroscopy in art and archaeology

“…Powdered pigments found in bowls from the Pompeii archaeological site and some wall painting fragments from Vesuvian area (conserved in the National Archaeological Museum of Naples) were investigated by Aliatis et al [24] using microscopic Raman and FTIR spectroscopies, XRD and SEM-EDX. Apart from the common pigment materials expected for the Roman wall paintings, some unexpected pigments and mixtures were identified, namely, (a) huntite (CaMg 3 (CO 3 ) 4 ) in a white powder found in a bowl, (b) Celadonite found in the green samples from the wall paintings, together with Egyptian blue and basic lead carbonate and (c) a mixture of malachite, goethite, Egyptian blue, hematite, carbon, cerussite and quartz in a heterogeneous green pigment in another bowl.…”