Influence des solvants aromatiques sur les propriétés optiques du bleu de phtalocyanine de cuivre en milieu pictural

peer reviewedActuellement, cinq formes de bleu de phtalocyanine de cuivre sont utilisées comme pigments artistiques: PB15, :1, :2, :3, :4, et :6. PB15 qui correspond à la forme la plus utilisée après PB15 :3 est sujette à la cristallisation. Ce phénomène qui s’observe plus particulièrement en présence de solvants aromatiques entraîne un glissement de teinte du bleu vers le vert et une perte du pouvoir couvrant du pigment. Or, l’usage de solvants aromatiques dans le champ de la conservation-restauration de peintures de chevalet est relativement commun. Citons par exemple, le toluène et les xylènes qui entrent dans la composition de certains mélanges de solvants, de certains types vernis (Laropal A81) et d’adhésifs (Beva 371). C'est pourquoi il est nécessaire d’effectuer une recherche de manière à déterminer si les conditions d’utilisation des solvants aromatiques en conservation-restauration provoquent la cristallisation de PB15. Dans cet article, les premiers résultats obtenus sur des échantillons de PB15, :1, :2, :3, :4 et :6 en poudre sont présentés. Les cinq formes susmentionnées ont été examinées sous microscope polarisant et analysées par spectroscopie infrarouge à transformée de Fourier et diffraction de rayons X, avant et après leur immersion dans les solvants aromatiques, de façon à pouvoir comparer les propriétés optiques et chimiques.NACH

Polyurethane coatings in 20th century outdoor painted sculptures: discrimination of major subgroups by means of ATR-FTIR spectroscopy

Like acrylics and alkyds, polyurethanes (PUs) represent an important class of industrial paints adopted by 20th and 21st artists; primarily by those creating outdoor painted sculptures (OPS). Because PU coatings offer a compromise between aesthetic and performance expectations, unachievable with other types of paints, they are commonly recognized as the most appropriate option for painted artworks intended for an outdoor setting. However, the PU class includes various systems and subgroups possessing very different properties, for instance two package solvent-borne, two package water-borne, one package water-borne and fluoropolymer polyurethanes. The present research aims to provide to the conservation professionals a better understanding of the versatility and diversity of PU coatings through compositional information and to outline markers helpful to differentiate the major PU subgroups from OPS by means of ATR-FTIR spectroscopy. The ATR-FTIR study conducted on a wide range of PU reference materials from the Getty Conservation Institute (GCI) reference collection highlights the relevance of this routine analytical method to discriminate certain subgroups of PU coatings. Indeed, by investigating well-known specimen it was possible to outline diagnostic FTIR features for three specific systems; fluoropolymer PU, one package water-borne PU made from acrylic latexes and two package water-borne PU prepared with PU dispersions. Furthermore, the FTIR measurements performed on various activators and co-reactants emphasizedthesignificantcontributionofthepolyisocyanateabsorptionsinthespectraofthe activated two package PU systems. However, the results obtained for various unmodified and water dispersible HDI polyisocyanate activators showed that the FTIR-ATR technique does not allow the discrimination within both types

Towards portable X-ray spectroscopic imaging of Palaeolithic cave art. Insights into used pigments and wall taphonomy at three Palaeolithic key cave sites

Palaeolithic cave art has taken a more and more important place in our cultural heritage. Its preservation is one of the major issues and involves necessarily a better understanding of the cave environments and of their evolution over time. However, the on-site geo-physico- chemical study of archaeological record stays dif cult and the conservation of its integrity imposes restrictions. Taking bene t of recent analytical developments in the X-ray eld, new perspectives of acquiring statistically relevant data for archaeological interpretation directly in the eld are provided by the implementation of portable and non-invasive characterization methods. It allows the improvement of archaeological and physico-chemical knowledge about the pigments used, the evaluation of the state of wall decorated surfaces over time and a better assessment of the relationship between pigment and wall support. For these purposes, complementary self-built portable spectrometers (X-ray uorescence in one and two dimensional mode, X-ray diffraction) are combined to perform qualitative and quantitative characterization of the pigments and cave walls as well as for chemical imaging on a decimetre scale. By using this combination of portable instruments the feasibility of analysis under very dif cult conditions speci c to the cave environments (humidity, temperature, dif cult access to the caves and to the decorated panels) was shown. Special spectrum evaluation procedures have been developed to take into account the heterogeneity of the cave walls in order to gain reliable data for chemical characterisation. The ef ciency of the analytical procedure has been demonstrated for three major cave sites featuring Palaeolithic art: Font-de-Gaume and Rouf gnac cave in Dordogne (France) and La Garma in Cantabria (Spain). A large assortment of colours can be observed in these caves (red, black, yellow and purple), associated to different mineral phases (iron and/or manganese oxides, charcoal and mixtures). Their detailed characterization provides an improved comprehension of the pictorial techniques used. Furthermore, it allows a better comparison between representations in a same cave, giving more detailed insights into its pictorial homogeneity and the different execution phases of its gures. As an example, the results obtained at Rouf gnac cave showed that heterogeneous mixtures of manganese oxides have been employed to design the 65 Great Ceiling gures whereas a unique pigment mixture has been used for the drawing of the Ten Mammoths Frieze. Further information has been obtained on the taphonomic wall processes. The spectroscopic study of these cave art illustrate the strong potential of such combined in situ and non-invasive analyses to better characterize the prehistoric gures in their cave environment and in a wider perspective to better understand the symbolic practices of past societies, appreciate possible cultural changes and relationships within the Franco-Cantabrian region

Compte rendu de Restauration et non-restauration en art contemporain 2

Cécile Dazord « L’art contemporain confronté aux phénomènes d’obsolescence technologique - ou l’impact des évolutions technologiques sur la préservation des œuvres d’art contemporain », in Restauration et non-restauration en art contemporain, dir. Marie-Hélène Breuil, Actes de journées d’études des 14 février et 6 avril 2007, École des Beaux Arts de Tours, 2008, pp. 57-71 Sous le titre Restauration et non-restauration en art contemporain sont rassemblés et publiés les actes des deux journées ..

Exploration des fonds : La famille Soler de Pablo Picasso

Histoire matérielle de l’oeuvreEn juin 1939, se tint entre les murs de la galerie Theodore Fischer, à Lucerne, la très controversée vente aux enchères de peintures et sculptures de maîtres modernes provenant des musées allemands : formule pudique qui désignait en réalité une vente destinée à débarrasser les musées allemands d’un art considéré comme dégénéré, autrement dit, non conforme à l’idéologie du Troisième Reich. Parmi les cent vingt-cinq œuvres mises en vente se trouvait le portrait de..

Future Talks,

La conservation des matériaux modernes et les difficultés qui la caractérisent étaient l’objet du colloque international Future Talks, organisé par Die Neue Sammlung, The International Design Museum, les 22 et 23 octobre 2009 à Munich. Conservateurs-restaurateurs spécialisés, représentants des  institutions muséales les plus prestigieuses d’Europe et d’outre-Atlantique ainsi que chercheurs en sciences appliquées y ont présenté leurs travaux et recherches. En matière de design, d’art moderne e..

Restauration et non-restauration en art contemporain 2,

La diversification autant que la profusion des matériaux et techniques mis en œuvre dans le champ de la création artistique actuelle implique le collectage d’une documentation tout aussi riche et diversifiée de la part des responsables de collection.  Documenter l’art contemporain, c’est précisément sur ce thème que s’est clôturé le 5 juin 2008,le cycle des journées d’étude organisé par la section conservation-restauration des œuvres sculptées de l’École supérieure des beaux-arts de Tours (Es..

Influence des solvants aromatiques sur les propriétés optiques du bleu de phtalocyanine de cuivre en milieu pictural

Currently, five forms of copper phthalocyanine blue, PB15, :1, :2, :3, :4, and :6, are used as artistic pigments. PB15, the most widespread form afterwards PB15:3 is prone to crystallisation. This phenomenon changes the metastable α form into a coarsely crystalline form with an attendant loss of tinctorial strength. Crystal growth can occur in many media but is most often seen in paints containing aromatic solvents. The use of aromatic solvents as part of conservation treatments of paintings is relatively common. For example, the toluene and  the xylenes found in  lining adhesives (as Beva 371), of some types varnish (as Laropal A81), and several mix of solvents used for cleaning or removal of the varnish. In conclusion, a search must be undertaken to determine if the conditions of use of aromatic solvents in conservation involves the crystallisation of PB15.In this paper  we will present the first results corresponding to the study of PB15, :1, :2, :3, :4, :6. These fives forms have been examined by polarized light microscopy and analysed with Fourier transform IR spectroscopy and X ray diffraction  in order to compare optical and chemical properties before and after they have been in contact with aromatic solvents