Studies on the effects of mixed light-thermal ageing on parchment by vibrational spectroscopy and micro hot table method

Abstract The damaging effects of mixed light-thermal ageing on parchment were studied by exposing mock-ups to artificial light (162 W/m2 irradiance) at controlled temperature and relative humidity (52 °C, 30% RH) for up to 748 h, with testing being made during this time incrementally. The physical–chemical changes (deterioration) resulting from these conditions were analysed by applying FTIR-ATR and Raman spectroscopy, colorimetric measurements and MHT. The deterioration found includes the formation of collagen-destabilised intermediate states which then progressively convert to disorganised structures, e.g. pregelatinised collagen and gelatin. The process is characterized by molecular changes of collagen associated with its photo-oxidation. These are shown by changes in the position and intensity of the main FTIR absorption bands of collagen, namely those of Amide I, Amide II, and Amide III, as well as by the occurrence and the increase of a shoulder at 1740 cm−1. The shrinking activity of the collagen fibres in the parchment mock-ups was measured by the micro-hot-table (MHT) method, which revealed the presence of multiple collagen populations with distinct thermal stabilities and confirmed the deterioration pattern suggested by the molecular changes

What about Phenol Formaldehyde (PF) Foam in Modern-Contemporary Art? Insights into the Unaged and Naturally Aged Material by a Multi-Analytical Approach

The ageing behavior of phenol formaldehyde (PF) foam, a material increasingly used in modern‐contemporary art, was investigated by a multi‐analytical approach. PF foams with open and closed‐cell structures were selected and analyzed in their unaged and naturally indoor‐aged state by employing optical microscopy (OM) and fiber optical reflectance spectroscopy (FORS) for assessing their morphology and color alteration. Micro‐Fourier transform infrared spectroscopy (μ‐ FTIR) was used for determining chemical changes and oxidation processes, and the acidity was monitored by pH measurements. The results clearly showed the extreme sensitivity of both open and closed‐cell PF foams to conditions typically found in indoor museums. OM indicated that the cells of the foams are prone to disrupt, and a tendency towards a red color shift was observed with FORS. μ‐FTIR revealed the formation of quinone groups resulting from oxidation reactions. Finally, a slight decrease in the acidity was found by pH measurements.The ageing behavior of phenol formaldehyde (PF) foam, a material increasingly used in modern‐contemporary art, was investigated by a multi‐analytical approach. PF foams with open-and closed‐cell structures were selected and analyzed in their unaged and naturally indoor‐aged state by employing optical microscopy (OM) and fiber optical reflectance spectroscopy (FORS) for assessing their morphology and color alteration. Micro‐Fourier transform infrared spectroscopy (μ‐ FTIR) was used for determining chemical changes and oxidation processes, and the acidity was monitored by pH measurements. The results clearly showed the extreme sensitivity of both open-and closed‐cell PF foams to conditions typically found in indoor museums. OM indicated that the cells of the foams are prone to disrupt, and a tendency towards a red color shift was observed with FORS. μ‐FTIR revealed the formation of quinone groups resulting from oxidation reactions. Finally, a slight decrease in the acidity was found by pH measurements

Linking of Cu(I) units by tetrahedral Mo2E2 complexes (E = P, As)

The reaction of [Cp2Mo2(CO)(4)(mu,eta(2:2)-E-2)] (A: E=P,B: E=As, Cp=C5H5) with the WCA-containing Cu(I)salts ([Cu(CH3CN)(4)][Al{OC(CF3)(3)}(4)] (CuTEF,C), [Cu(CH3CN)(4)][BF4] (D) and [Cu(CH3CN)(3.5)][FAl{OC6F10(C6F5)}(3)] (CuFAl,E)) affords seven unprecedented coordination compounds. Depending on the E(2)ligand complex, the counter anion of the copper salt and the stoichiometry, four dinuclear copper dimers and three trinuclear copper compounds are accessible. The latter complexes reveal first linear Cu(3)arrays linked by E(2)units (E=P, As) coordinated in an eta(2:1:1)coordination mode. All compounds were characterized by X-ray crystallography, NMR and IR spectroscopy, mass spectrometry and elemental analysis. To define the nature of the Cu...Cu...Cu interactions, DFT calculations were performed

Discrete and polymeric organometallic‐organic hybrid materials based on the diphosphorus complex [Cp₂Mo₂(CO)₄(η²‐P₂)], Cu salts, and 2,2′‐bipyrimidine

The reaction of the diphosphorus complex [Cp2Mo2(CO)(4)((2)-P-2)] (1), with the Cu-I salts [Cu(CH3CN)(4)][BF4] or [Cu(CH3CN)(4)][PF6], and a mixture of [Cu(CH3CN)(4)][BF4] and CuCl in the presence of 2,2-bipyrimidine (2) is studied. Depending on the Cu-I salts used and the layering solvent involved in the crystallisation, a variety of novel coordination compounds are accessible in moderate to excellent yields (26-80%): the novel dicationic molecular organometallic-organic hybrid complexes [{Cp2Mo2(CO)(4)(mu(3),(1:2:2)-P-2)}(4)(mu(2),(1:1:1:1)-C8H6N4)Cu-2][BF4](2) (3) and [{Cp2Mo2(CO)(4)(mu(3),(1:2:2)-P-2)}(2){Cp2Mo2(CO)(4)(mu(3),(2:2:2)-P-2)}(2)(mu(2),(1:1:1:1)-C8H6N4)Cu-2][PF6](2) (4), the unique neutral 1D organometallic-organic hybrid polymer [{Cp2Mo2(CO)(4)(mu(4),(1:1:2:2)-P-2)}(2)(mu(2),(1:1:1:1)-C8N6N4)(CuCl)(2)](n) (5) and the unprecedented 2D organometallic-organic hybrid polymer [{Cp2Mo2(CO)(4)(mu(4),(1:1:2:2)-P-2)}(mu(2),(1:1:1:1)-C8H6N4){Cu-2(mu-Cl)}](2)[BF4](2n) (6)

Investigation of ancient gold objects from Artemision at Ephesus using portable µ-XRF

During two measurement campaigns in the Archaeological Museum in Istanbul and the Ephesus Museum in Selçuk, Turkey, more than 80 ancient gold objects (e.g. appliqués, statuettes and coins) from the 8th-6th centuries BC were analyzed using portable XRF instruments in order to obtain information on the chemical composition and homogeneity of the artefacts discovered during excavations in the sanctuary of Artemis at Ephesus. These results and complementary studies on the manufacturing techniques employed for making these objects will contribute to our knowledge of metalworking, trade, as well as the transfer of ideas and technologies at Ephesus and in Western Asia in the Archaic period. The objects can be characterized as homogeneous alloys, mainly consisting of gold (Au), silver (Ag) and copper (Cu). A high compositional variation of Au and Ag between different objects could be determined (Au between 48.7 and 99.9%, Ag between <detection limit (dl) and 50.9%, Cu between <dl and 4.4%). These results demonstrated the range of gold alloys represented within the collection and allowed a discrimination between natural and artificial gold alloys (including the identification of ‘refined’ gold). In some cases, objects which were closely related from a typological, stylistic and/or technological point of view were also similar in composition, differing only in the sub-percent range.Plus de 80 objets anciens en or (p.ex. appliques, statuettes et monnaies) datés du viiie-vie siècle av. J.-C. et trouvés lors des fouilles du sanctuaire d’Artémise à Ephèse, ont été analysés au moyen d’un équipement de FX portable pendant les deux campagnes de mesure réalisées au musée archéologique d’Istanbul et au musée d’Ephèse à Selçuk, Turquie, de façon à obtenir des informations sur leur composition chimique et sur leur homogénéité. Ces résultats, complémentés par des études sur leurs techniques de fabrication, contribuent à la connaissance du travail du métal, de son commerce, ainsi que du transfert d’idées et technologies à Ephèse et dans l’Asie de l’Ouest pendant la période Archaïque. Les objets ont été fabriqués avec des alliages homogènes, se composant en majorité d’or (Au), argent (Ag) et cuivre (Cu). Une forte variation de teneurs a pu être mise en évidence pour l’Au et l’Ag dans le cas de différents objets (Au entre 48,7 and 99,9 %, Ag entre < limite de détection (dl) et 509 %, Cu entre < dl et 4,4 %). Ces résultats montrent la gamme d’alliages d’or de la collection et permettent de discriminer entre alliages d’or naturels et artificiels (en incluant l’identification d’or « affiné »). Dans certains cas d’objets de typologie, style et/or techniques de fabrication proches, leurs compositions sont identiques, la différence n’apparaissant qu’au niveau du sous-pourcent

Multianalytical Approach to explain the darkening process of hematite pigment in paintings from ancient Pompeii after accelerated weathering experiments

[EN] In this paper, recently excavated fresco painting fragments from the House of Marcus Lucretius (Pompeii) and not exposed to the atmosphere since the eruption of the Mount Vesuvius were subjected to a controlled SO2 atmosphere and high relative humidity. These experiments were conducted in order to simulate under accelerated conditions the possible deterioration of the hematite pigment and plaster. The mineralogical transformation of the polychromy and plaster was monitored using mainly Raman spectroscopy, a non-destructive technique, but also infrared spectroscopy (FT-IR) and scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS). After different exposure cycles to SO2, it was confirmed that hematite red pigment (Fe2O3) can be reduced into magnetite (Fe3O4), which provides the darkened colour to the pigment. While Fe(III) from hematite is reduced into Fe(II) or mixed Fe(III) and Fe(II), the SO2 can be oxidized (SO3) and hydrated to experience a subsequent wet deposition (H2SO4 aerosol) causing also the transformation of calcite into gypsum. Finally, it was assessed that high concentrations of SO2 can also cause the sulphation of hematite pigment promoting its transformation into paracoquimbite/coquimbite (Fe2(SO4)3$9H2O). Moreover, in some areas of the deteriorated painting fragments, non-expected iron(II) sulphate and sulphite species were also identified