Between 1924 and 1947, Gino Severini decorated five churches in the Romand region of Switzerland ... more Between 1924 and 1947, Gino Severini decorated five churches in the Romand region of Switzerland with monumental religious wall paintings. This mural art played an important role in the Italian artist's career despite being mostly unknown and not easily found. The painting methods and materials of these modern Swiss murals were characterized by combining historical and archival research with onsite visual and scientific examination. Most pigments were identified with noninvasive methods integrating mapping techniques (i.e., technical photography and digital microscopy) with point analysis (x‐ray fluorescence and reflection FT‐IR spectroscopy). The results of these portable techniques were completed with SEM‐EDS, μFT‐IR FPA imaging, and μRaman analyses on micro‐samples which provided stratigraphic and compositional information to complement the noninvasive results. Overall, the data obtained show that Severini used both traditional pigments (e.g., Sangiovanni white and ochres/earths of various color) and modern ones, such as cadmium‐based pigments, with different painting techniques (e.g., zinc white was applied exclusively a secco). Apart from cerulean blue (cobalt stannate) and Naples yellow (lead antimonate) found only in two locations, the same set of pigments was documented in all of Severini's Swiss murals. The characterization of the artist's palette is important to understand the technical painting process followed by Severini, his interest on new painting materials available on the market and, at the same time, loyalty towards traditional painting methods, such as painting a fresco.
Lead white is known as one of the oldest pigments in art and can be used as a dating material. Up... more Lead white is known as one of the oldest pigments in art and can be used as a dating material. Upon production following the Stack process, the 14 C isotope of atmospheric carbon dioxide is fixed in the carbonate, and its radiocarbon dating can be used as a proxy for the age of a painting. The previously reported carbonate hydrolysis protocol reaches its limitation when confronted with samples presenting a mixture of carbonates, such as lead carbonate (cerussite or hydrocerussite), calcium carbonate (calcite), and/or calcium magnesium carbonate (dolomite). Thermogravimetric analyses indicate that decomposition of lead carbonate can be achieved at 350°C in TGA diagrams, as other mineral carbonates only decompose to carbon dioxide at temperatures above 700°C. Thus, a thermal approach is proposed to separate the various carbonates and isolate the specific 14 C signature to the lead carbonate. In practice, however, discrepancies between the measured radiocarbon ages and expected ages were observed. FTIR analyses pointed to the formation of metal carboxylates, an indicator that the organic binder is not inert and plays a role in the dating strategy. Upon drying, oxidation and hydrolysis take place leading to the formation of free fatty acids, which in turn interact with the different carbonates upon heating. Their removal was achieved by introduction of a solvent extraction step prior to the thermal treatment, which was confirmed by GC-MS analyses, and thus, the collected carbon dioxide at 350°C results can be assigned correctly to the decomposition of the lead white pigment. The proposed procedure was furthermore verified on mixed carbonate-bearing paint samples collected from a Baroque oil painting.
An artwork often is a complex, multilayered and multicomponent system build-up. Chemical interact... more An artwork often is a complex, multilayered and multicomponent system build-up. Chemical interaction between these components and layers, which age over time, influenced by environmental conditions, can lead to reactions that alter the visual impression, the integrity and the materials of an artwork. Conservation science is thus confronted with alterations at different interfaces and levels such as for example the pigment–environment (e.g. Cato et al. 2017), pigment-binder (Fig. 1, Ferreira et al. 2015) and the varnish-environment (e.g. Soulier et al. 2012) interface. To learn more about these phenomena, our current strategy is minimally invasive, combines the complementary techniques of infrared imaging (ATR-FTIR-FPA), Raman spectroscopy and scanning electron microscopy (VP-SEM, SE/BSE/EDS), applied sequentially to micro-samples. This combination not only covers a wide range of materials, but also delivers morphological and 2D stratigraphic information from minimal amounts of sample material. With respect to pigment identification on micro samples, Raman has many strong advantages in tracking down pigment traces, both inorganic and synthetic organic pigments. It probably even may be called ‘THE’ technique, when it comes to synthetic organic pigment detection and identification (e.g. Scherrer et al. 2009). Yet, in many cases, Raman cannot rely on simple routine measurements. This presentation gives some insight into non-standard behaviour at the laser-pigment interface and possible approaches to retrieve a useful spectrum. Literature References Cato E. et al. (2017). J Raman Spectrosc 1-10. doi.org/10.1002/jrs.5256 Ferreira E. et al. (2015). Herit Sci 3(1): 1-11. doi.org/10.1186/s40494-015-0052-3 Scherrer et al. (2009). Spectroc. Acta Pt. A-Molec. Biomolec. Spectr. 505-524. doi.org/10.1016/J.Saa.2008.11.029 Soulier et al. (2012). Z Kunsttechnol Konserv 108-117. https://www.hkb.bfh.ch/en/conservation-and-restoration/consulting-services
Zeitschrift für Kunsttechnologie und Konservierung, 2022
Adhesive meshes are micro-structured and honeycomb-shaped, flexible adhesive nets. They can be pr... more Adhesive meshes are micro-structured and honeycomb-shaped, flexible adhesive nets. They can be produced from a variety of adhesives such as water-soluble methylcelluloses or sturgeon glue. These two have proofed long-term stability for several decades now and have found wide application in the field of conservation. If a painting allows for temporary use of moisture, adhesive meshes provide an interesting alternative to common adhesives, such as acrylic dispersions and hot-melt adhesives, as their application does require neither heat nor organic solvents. The dry adhesive meshes are positioned in place and activated using a controlled supply of water. Depending on the accessibility of the bonding area, water can be sprayed or applied by a suitable carrier material like capillary non-wovens. After activation, the parts are joined under light pressure until dry. This technique provides an exceptionally uniform distribution of the adhesive throughout the bonding surface, a permeable and reversible bonding, and as such assuring a minimally invasive and highly controllable treatment. So far, several case studies underpin the practical applicability, comprising strip lining, full linings, the application of small patches at the tacking margin or the re-attachment of failing historic linings along the edges. Originating from a diploma project at the Dresden University of Fine Arts (HfBK Dresden), Germany, adhesive meshes were further investigated within a research project at the Bern University of Applied Sciences in cooperation with APM Technica AG, both Switzerland, and the HfBK Dresden. The outcome was an improved production process, commercial availability of adhesive meshes, and widening the product range by investigating basic adhesive properties of methylcellulose meshes. This current contribution explored adhesive meshes made of Methocel™ A4C (400 mPa·s) and Methocel™ A15LV (15 mPa·s) with respect to material and adhesive properties in comparison to the physical behavior of BEVA® 371 films. Commercial adhesive meshes, mass-produced by APM Technica, were compared to self-made adhesive meshes, manufactured using a laser-cut silicone mold. Canvas specimens were bonded with adhesive meshes, activated using a standardized spraying technique for laboratory tests. Bonding properties were determined by lap shear tests according to DIN EN 1465 that was adapted to canvas specimens. The results show that adhesive strength varies depending on the amount of activation water and the viscosity of the methylcellulose. Commercial and self-made adhesive meshes show similar tendencies despite the different weight per unit area (grammage). Both manufacturing modalities resulted in similar trends in bond strength. Due to the overall lower grammage, self-made Methocel™ A4C adhesive meshes require smaller amounts of water for activation, whereas APMˈs adhesive meshes are capable of higher maximum adhesive bond strengths when activated sufficiently. In general, the bond strength of adhesive meshes made from medium-viscosity Methocel™ A4C increases with the amount of activation water and can be adjusted over a wide range from slight to very strong adhesion. A moderate amount of activation water of ≥200 g/m² results in high to very high bond strengths, which are equal to and even exceed those of BEVA® 371 films. Adhesive meshes made from the low-viscosity Methocel™ A15LV achieve lower bond strengths, yet require smaller amounts of water ≤200 g/m² for activation. A higher water input leads to dissolution of the mesh, to a deeper penetration of the glue into the canvas and finally to a decrease in bond strength. In conclusion, adhesive meshes made from Methocel™ A4C meet the requirements when canvas bonding needs to withstand high tensile stress, e.g. with strip lining. Methocel™ A15LV meshes are, on the other hand, particularly suited to attach smaller patches exposed to low or moderate stress. They proved suitable for poorly accessible bonding surfaces and water-sensitive materials where only a minimum of humidity is acceptable.
Bereits seit dem frühen 20. Jahrhundert sind synthetisch organische Pigmente in kommerziellen Kün... more Bereits seit dem frühen 20. Jahrhundert sind synthetisch organische Pigmente in kommerziellen Künstlerfarben verwendet worden. In den heutigen Künstler- und Anstrichfarben haben diese die anorganischen Pigmente weitgehend verdrängt und machen den überwiegenden Anteil der Bunttöne in Künstlerfarben aus. Diese Tatsache bringt neue Konservierungsproblematiken moderner Künstlerfarben mit sich. Im Gegensatz zu den klassischen Ölfarben, wo die Lösemittelempfindlichkeit der Malfarben stark durch die Bindemitteleigenschaften dominiert sind, erweisen sich die Empfindlichkeiten der modernen Künstlerfarben als bedeutend komplexer. Insbesondere die Lösemittelempfindlichkeit der organischen Pigmente stellt eine neue Problematik für die Konservierungs- und Restaurierungspraxis dar. In diesem Kontext wurde die Lösemittelempfindlichkeit von synthetisch organischen Pigmenten und entsprechend pigmentierten Ölfarben untersucht. Die Arbeit fokussiert sich auf 23 Pigmente, welche kunsttechnologisch von Bedeutung sind. Die Auswahl erfolgte nach historischen und technologischen Kriterien. Dabei wurde darauf geachtet, dass die verschiedenen Farbtöne und unterschiedlichen Materialklassen abgedeckt wurden. Die Untersuchungen erfolgten mit verschiedenen Lösemitteln mit spezifischer Wechselwirkungsfähigkeiten, um selektive Bewertungen der Pigmentempfindlichkeit über das Polaritätsspektum zu ermitteln. Die Untersuchungen der zeitabhängigen Löslichkeiten erfolgten mit UV-VIS Spektrometrie an gealterten Farben. Das Löslichkeitsverhalten der reinen Pigmente und der entsprechend pigmentierten Künstlerfarben wurden quantitativ verglichen. Dabei wurden die verschiedenen Einflussfaktoren wie beispielsweise die Quellwirkung der Polymermatrix des Bindmittels erfasst und bewertet. Die verschiedenen Farbmittel unterscheiden sich stark voneinander. Weiter wurden morphologische Strukturveränderungen durch Farbmittelextraktionen aus den Malfarben mittels FTIR- und Raman-Spektrometrie, sowie Rasterelektronenmikroskopie charakterisiert. Basierend auf diesen Untersuchungen lassen sich generelle Aussagen zur Lösemittelempfindlichkeiten organisch pigmentierter Ölfarben ableiten
The surface of an artwork is the interface to its environment and its viewer. The choice of a spe... more The surface of an artwork is the interface to its environment and its viewer. The choice of a specific behaviour and appearance by the artist is an essential part of the making and – of how we perceive the expression of the artist. Colour hue and intensity, reflectivity, surface structure, surface finishing and protection, etc. are elemental properties that are achieved with an often complex, multilayered and multicomponent system build-up of paintings or painted and varnished artwork. Chemical interaction between these components and layers, which age over time, influenced by environmental conditions, can lead to reactions that alter the visual impression and/or integrity of an artwork. Conservation science is thus confronted with alterations at different interfaces and levels such as for example the pigment–environment (e.g. Cato et al. 2017), pigment-binder (Fig. 1, Ferreira et al. 2015) and the varnish-environment (e.g. Soulier et al. 2012) interface. Contrary to the development of new materials, understanding and reconstructing the past is generally hampered by alterations through time, poor or lost documentation, the limited availability of sample material that is scarce and, in the case of e.g. paintings or musical instruments, is barely accessible due to the high value of the objects. Furthermore, the experimental nature of the artists leads to the situation where the analyst is confronted with non-standardised materials and unconventional working techniques, such as for example the “tempera” painting technique (e.g Zumbühl et al. 2014; Ferreira et al. 2015). The variety of painted substrates (paper, polymer, textile, leather, wood, metal, glass, rock, mortar…) also implies that we have to deal with a wide range of surface properties and interface behaviour. Generalised approaches thus end in casework when it comes to interpretation of analytical data. The lack of historic reference material may lead to experimental re-production according to ancient recipes, in the case of Guignet green unveiling temperature dependant surface behaviour of pigment particles and as such variable end products (Zumbühl et al. 2009). Our current strategy is minimally invasive, combines the complementary techniques of infrared imaging (ATR-FTIR-FPA), Raman spectroscopy and scanning electron microscopy (VP-SEM, SE/BSE/EDS), applied sequentially to micro-samples. This combination not only covers a wide range of materials, but also delivers morphological and 2D stratigraphic information from minimal amounts of sample material. Specific developments such as the methodology to derivatise interfering compounds prior to FTIR measurement have further helped to significantly increase the selectivity of infrared spectroscopy and reach a new level of information in reconstructing historic coatings (Zumbühl et al. 2017). Figure 1. a) ‚Portrait of a young girl’ by Filippo Franzoni (ca. 1888, oil on canvas). b) Close-up view of the surface showing ‚gold’ particles turning green. c-e) crosssection of metal particle showing alteration products from pigment-binder interaction. (Ferreira et al. 2015) Literature References Cato E. et al. (2017) J Raman Spectrosc 1-10. doi.org/10.1002/jrs.5256 Ferreira E. et al. (2015) Herit Sci 3(1): 1-11. doi.org/10.1186/s40494-015-0052-3 Ferreira E. et al. (2016) In: Beltinger K. & Nadolny J. (Eds) KUNSTmaterial 4, Archetype Pub., Zürich, 205-227. Soulier et al. (2012). Z Kunsttechnol Konserv 108-117. Zumbühl S. et al. (2009) Stud Conserv 54, 149-159. doi.org/10.1179/sic.2009.54.3.149 Zumbühl S. et al. (2014) Appl Spectrosc 68(4): 458-465. doi.org/10.1366/13-07280 Zumbühl, S. et al. (2017) Microchem J 134, 317-326. doi.org/10.1016/j.microc.2017.06.013 https://www.hkb.bfh.ch/en/campus/art-technological-laboratory
L'usage de métal réduit en poudre dans les métiers d'art est attesté dès le haut Moyen âg... more L'usage de métal réduit en poudre dans les métiers d'art est attesté dès le haut Moyen âge. C'est à l'ère du baroque tardif et du rococo que la poudre métallique a connu son apogée comme procédé de revêtement. Puis les artistes préromantiques et symbolistes ont découvert les possibilités picturales offertes par la poudre métallique.
During the examination of two 19th century oil paintings by Swiss artists, the Reading pastor (ca... more During the examination of two 19th century oil paintings by Swiss artists, the Reading pastor (ca. 1885) by Ferdinand Hodler (1853-1918) and Portrait of a young girl (ca. 1888) by Filippo Franzoni , it was observed that in particular locations, the surface had an unusually granular texture, given by the application of metallic particles and the presence of large translucent green agglomerates. In this paper we investigate the composition and origin of the metal particles and green agglomerates. A combination of bulk analysis (GC-MS and FTIR) and analytical microscopy techniques (X-ray tomographic microscopy, light microscopy, ATR-FTIR-FPA imaging and SEM-EDX) were used. It was concluded that the metal particles are composed of a lower quality brass (copper/zinc alloy) and ground from foil. The current appearance resulted from the reaction of the brass and its corrosion products with the fatty acids in the surrounding paint/varnish matrix. This has lead to the formation of agglomerates of zinc and copper carboxylates, the latter responsible for their green colour.
Cleaning strategies in restoration and conservation often involve the use of solvent mixtures, de... more Cleaning strategies in restoration and conservation often involve the use of solvent mixtures, despite the fact that the interaction between these and the objects under treatment is not always well known. Binary solvent mixtures behave nonideally; that is, the properties are not directly proportional or related to the mixing ratio. This fact contradicts the trivialized solubility charts, for example, the Teas chart, known and applied in practical restoration. The description of the dissolving action of binary systems therefore requires additional information such as the solvation and solubilization mechanisms involved. The effects of binary solvent mixtures on oil and alkyd paints were systematically investigated, with particular focus on the swelling action and leaching of binding media components. In total, 75 binary mixtures made from the solvents nhexane, toluene, chloroform, diethyl ether, acetone, and ethanol were experimentally applied to free paint films by immersion. The so...
Zwischgold (also part-gold in English) is a two-layered metal foil made of gold and silver that w... more Zwischgold (also part-gold in English) is a two-layered metal foil made of gold and silver that was historically applied to altarpieces, sculptures and panel paintings. It tends to oxidize quickly in air and therefore was usually applied with a protective varnish layer. The purpose of applying Zwischgold is an interesting topic in the research of art history and art technologies. The identification of Zwischgold helps to define its application areas and thus the purpose of its application. However, when the Zwischgold surface is still well preserved, it can be challenging to differentiate it from surfaces applied with gold foils. In this paper, we present a handheld XRF analyser, "Niton XL3t GOLDD+", for a qualitative identification of Zwischgold surfaces. Its performance has been evaluated through measurements of Zwischgold models and also a 15-century altar figure applied with Zwischgold. The identification of Zwischgold by the "Niton XL3t GOLDD+" has proven to...
Effective and responsible use of solvents is an important competence of a conservator/restorer. T... more Effective and responsible use of solvents is an important competence of a conservator/restorer. The goal to selectively remove components such as varnishes from the surface without affecting underlying paint is a common challenge in the field of restoration. The complexity of the processes of solvation and dissolution has given rise to several approaches by various groups to simplify solvent action and deliver some selection criteria to the restorer. In general, however, these approaches lack both a qualitative and quantitative description of the dissolution processes. In the context of practical conservation needs, knowledge of the rate of solvent action will decide the ability to control a conservation treatment. Since the kinetics of solvent action mainly depend on an entropy change in the dissolving process, a different approach is necessary to satisfy the demands of current conservation practice.
During the examination of two 19th century oil paintings by Swiss artists, the Reading pastor (ca... more During the examination of two 19th century oil paintings by Swiss artists, the Reading pastor (ca. 1885) by Ferdinand Hodler (1853–1918) and Portrait of a young girl (ca. 1888) by Filippo Franzoni (1857–1911), it was observed that in particular locations, the surface had an unusually granular texture, given by the application of metallic particles and the presence of large translucent green agglomerates. In this paper we investigate the composition and origin of the metal particles and green agglomerates. A combination of bulk analysis (GC–MS and FTIR) and analytical microscopy techniques (X-ray tomographic microscopy, light microscopy, ATR–FTIR–FPA imaging and SEM–EDX) were used. It was concluded that the metal particles are composed of a lower quality brass (copper/zinc alloy) and ground from foil. The current appearance resulted from the reaction of the brass and its corrosion products with the fatty acids in the surrounding paint/varnish matrix. This has lead to the formation of...
Augusto Giacometti’s painting The Circling of the Planets (1907; 268 × 218 cm) is in a highly fra... more Augusto Giacometti’s painting The Circling of the Planets (1907; 268 × 218 cm) is in a highly fragile state, suffering from widespread flaking paint. These flakes are very brittle and rigid; none of the usual consolidation techniques managed to achieve necessary ductility to secure lifting paint flakes. In the blue areas, both absorbent protein-oil (lean tempera), as well as non-absorbent oil-protein (tempera grassa) layers were revealed by FTIR analysis. Furthermore, numerous adhesive materials, like wax and PVAc from past conservation treatments, were detected. This paper discusses systematic experiments performed to develop a viscosity-adjusted consolidating filler to secure displaced paint flakes, without mobilising residues of old adhesives or penetrating the lean tempera paint. The properties were controlled to ensure high viscosity, minimal shrinkage, and no build-up of tensile stress, as this could be harmful to the fragile flakes. To apply such a consolidating filler precis...
Between 1924 and 1947, Gino Severini decorated five churches in the Romand region of Switzerland ... more Between 1924 and 1947, Gino Severini decorated five churches in the Romand region of Switzerland with monumental religious wall paintings. This mural art played an important role in the Italian artist's career despite being mostly unknown and not easily found. The painting methods and materials of these modern Swiss murals were characterized by combining historical and archival research with onsite visual and scientific examination. Most pigments were identified with noninvasive methods integrating mapping techniques (i.e., technical photography and digital microscopy) with point analysis (x‐ray fluorescence and reflection FT‐IR spectroscopy). The results of these portable techniques were completed with SEM‐EDS, μFT‐IR FPA imaging, and μRaman analyses on micro‐samples which provided stratigraphic and compositional information to complement the noninvasive results. Overall, the data obtained show that Severini used both traditional pigments (e.g., Sangiovanni white and ochres/earths of various color) and modern ones, such as cadmium‐based pigments, with different painting techniques (e.g., zinc white was applied exclusively a secco). Apart from cerulean blue (cobalt stannate) and Naples yellow (lead antimonate) found only in two locations, the same set of pigments was documented in all of Severini's Swiss murals. The characterization of the artist's palette is important to understand the technical painting process followed by Severini, his interest on new painting materials available on the market and, at the same time, loyalty towards traditional painting methods, such as painting a fresco.
Lead white is known as one of the oldest pigments in art and can be used as a dating material. Up... more Lead white is known as one of the oldest pigments in art and can be used as a dating material. Upon production following the Stack process, the 14 C isotope of atmospheric carbon dioxide is fixed in the carbonate, and its radiocarbon dating can be used as a proxy for the age of a painting. The previously reported carbonate hydrolysis protocol reaches its limitation when confronted with samples presenting a mixture of carbonates, such as lead carbonate (cerussite or hydrocerussite), calcium carbonate (calcite), and/or calcium magnesium carbonate (dolomite). Thermogravimetric analyses indicate that decomposition of lead carbonate can be achieved at 350°C in TGA diagrams, as other mineral carbonates only decompose to carbon dioxide at temperatures above 700°C. Thus, a thermal approach is proposed to separate the various carbonates and isolate the specific 14 C signature to the lead carbonate. In practice, however, discrepancies between the measured radiocarbon ages and expected ages were observed. FTIR analyses pointed to the formation of metal carboxylates, an indicator that the organic binder is not inert and plays a role in the dating strategy. Upon drying, oxidation and hydrolysis take place leading to the formation of free fatty acids, which in turn interact with the different carbonates upon heating. Their removal was achieved by introduction of a solvent extraction step prior to the thermal treatment, which was confirmed by GC-MS analyses, and thus, the collected carbon dioxide at 350°C results can be assigned correctly to the decomposition of the lead white pigment. The proposed procedure was furthermore verified on mixed carbonate-bearing paint samples collected from a Baroque oil painting.
An artwork often is a complex, multilayered and multicomponent system build-up. Chemical interact... more An artwork often is a complex, multilayered and multicomponent system build-up. Chemical interaction between these components and layers, which age over time, influenced by environmental conditions, can lead to reactions that alter the visual impression, the integrity and the materials of an artwork. Conservation science is thus confronted with alterations at different interfaces and levels such as for example the pigment–environment (e.g. Cato et al. 2017), pigment-binder (Fig. 1, Ferreira et al. 2015) and the varnish-environment (e.g. Soulier et al. 2012) interface. To learn more about these phenomena, our current strategy is minimally invasive, combines the complementary techniques of infrared imaging (ATR-FTIR-FPA), Raman spectroscopy and scanning electron microscopy (VP-SEM, SE/BSE/EDS), applied sequentially to micro-samples. This combination not only covers a wide range of materials, but also delivers morphological and 2D stratigraphic information from minimal amounts of sample material. With respect to pigment identification on micro samples, Raman has many strong advantages in tracking down pigment traces, both inorganic and synthetic organic pigments. It probably even may be called ‘THE’ technique, when it comes to synthetic organic pigment detection and identification (e.g. Scherrer et al. 2009). Yet, in many cases, Raman cannot rely on simple routine measurements. This presentation gives some insight into non-standard behaviour at the laser-pigment interface and possible approaches to retrieve a useful spectrum. Literature References Cato E. et al. (2017). J Raman Spectrosc 1-10. doi.org/10.1002/jrs.5256 Ferreira E. et al. (2015). Herit Sci 3(1): 1-11. doi.org/10.1186/s40494-015-0052-3 Scherrer et al. (2009). Spectroc. Acta Pt. A-Molec. Biomolec. Spectr. 505-524. doi.org/10.1016/J.Saa.2008.11.029 Soulier et al. (2012). Z Kunsttechnol Konserv 108-117. https://www.hkb.bfh.ch/en/conservation-and-restoration/consulting-services
Zeitschrift für Kunsttechnologie und Konservierung, 2022
Adhesive meshes are micro-structured and honeycomb-shaped, flexible adhesive nets. They can be pr... more Adhesive meshes are micro-structured and honeycomb-shaped, flexible adhesive nets. They can be produced from a variety of adhesives such as water-soluble methylcelluloses or sturgeon glue. These two have proofed long-term stability for several decades now and have found wide application in the field of conservation. If a painting allows for temporary use of moisture, adhesive meshes provide an interesting alternative to common adhesives, such as acrylic dispersions and hot-melt adhesives, as their application does require neither heat nor organic solvents. The dry adhesive meshes are positioned in place and activated using a controlled supply of water. Depending on the accessibility of the bonding area, water can be sprayed or applied by a suitable carrier material like capillary non-wovens. After activation, the parts are joined under light pressure until dry. This technique provides an exceptionally uniform distribution of the adhesive throughout the bonding surface, a permeable and reversible bonding, and as such assuring a minimally invasive and highly controllable treatment. So far, several case studies underpin the practical applicability, comprising strip lining, full linings, the application of small patches at the tacking margin or the re-attachment of failing historic linings along the edges. Originating from a diploma project at the Dresden University of Fine Arts (HfBK Dresden), Germany, adhesive meshes were further investigated within a research project at the Bern University of Applied Sciences in cooperation with APM Technica AG, both Switzerland, and the HfBK Dresden. The outcome was an improved production process, commercial availability of adhesive meshes, and widening the product range by investigating basic adhesive properties of methylcellulose meshes. This current contribution explored adhesive meshes made of Methocel™ A4C (400 mPa·s) and Methocel™ A15LV (15 mPa·s) with respect to material and adhesive properties in comparison to the physical behavior of BEVA® 371 films. Commercial adhesive meshes, mass-produced by APM Technica, were compared to self-made adhesive meshes, manufactured using a laser-cut silicone mold. Canvas specimens were bonded with adhesive meshes, activated using a standardized spraying technique for laboratory tests. Bonding properties were determined by lap shear tests according to DIN EN 1465 that was adapted to canvas specimens. The results show that adhesive strength varies depending on the amount of activation water and the viscosity of the methylcellulose. Commercial and self-made adhesive meshes show similar tendencies despite the different weight per unit area (grammage). Both manufacturing modalities resulted in similar trends in bond strength. Due to the overall lower grammage, self-made Methocel™ A4C adhesive meshes require smaller amounts of water for activation, whereas APMˈs adhesive meshes are capable of higher maximum adhesive bond strengths when activated sufficiently. In general, the bond strength of adhesive meshes made from medium-viscosity Methocel™ A4C increases with the amount of activation water and can be adjusted over a wide range from slight to very strong adhesion. A moderate amount of activation water of ≥200 g/m² results in high to very high bond strengths, which are equal to and even exceed those of BEVA® 371 films. Adhesive meshes made from the low-viscosity Methocel™ A15LV achieve lower bond strengths, yet require smaller amounts of water ≤200 g/m² for activation. A higher water input leads to dissolution of the mesh, to a deeper penetration of the glue into the canvas and finally to a decrease in bond strength. In conclusion, adhesive meshes made from Methocel™ A4C meet the requirements when canvas bonding needs to withstand high tensile stress, e.g. with strip lining. Methocel™ A15LV meshes are, on the other hand, particularly suited to attach smaller patches exposed to low or moderate stress. They proved suitable for poorly accessible bonding surfaces and water-sensitive materials where only a minimum of humidity is acceptable.
Bereits seit dem frühen 20. Jahrhundert sind synthetisch organische Pigmente in kommerziellen Kün... more Bereits seit dem frühen 20. Jahrhundert sind synthetisch organische Pigmente in kommerziellen Künstlerfarben verwendet worden. In den heutigen Künstler- und Anstrichfarben haben diese die anorganischen Pigmente weitgehend verdrängt und machen den überwiegenden Anteil der Bunttöne in Künstlerfarben aus. Diese Tatsache bringt neue Konservierungsproblematiken moderner Künstlerfarben mit sich. Im Gegensatz zu den klassischen Ölfarben, wo die Lösemittelempfindlichkeit der Malfarben stark durch die Bindemitteleigenschaften dominiert sind, erweisen sich die Empfindlichkeiten der modernen Künstlerfarben als bedeutend komplexer. Insbesondere die Lösemittelempfindlichkeit der organischen Pigmente stellt eine neue Problematik für die Konservierungs- und Restaurierungspraxis dar. In diesem Kontext wurde die Lösemittelempfindlichkeit von synthetisch organischen Pigmenten und entsprechend pigmentierten Ölfarben untersucht. Die Arbeit fokussiert sich auf 23 Pigmente, welche kunsttechnologisch von Bedeutung sind. Die Auswahl erfolgte nach historischen und technologischen Kriterien. Dabei wurde darauf geachtet, dass die verschiedenen Farbtöne und unterschiedlichen Materialklassen abgedeckt wurden. Die Untersuchungen erfolgten mit verschiedenen Lösemitteln mit spezifischer Wechselwirkungsfähigkeiten, um selektive Bewertungen der Pigmentempfindlichkeit über das Polaritätsspektum zu ermitteln. Die Untersuchungen der zeitabhängigen Löslichkeiten erfolgten mit UV-VIS Spektrometrie an gealterten Farben. Das Löslichkeitsverhalten der reinen Pigmente und der entsprechend pigmentierten Künstlerfarben wurden quantitativ verglichen. Dabei wurden die verschiedenen Einflussfaktoren wie beispielsweise die Quellwirkung der Polymermatrix des Bindmittels erfasst und bewertet. Die verschiedenen Farbmittel unterscheiden sich stark voneinander. Weiter wurden morphologische Strukturveränderungen durch Farbmittelextraktionen aus den Malfarben mittels FTIR- und Raman-Spektrometrie, sowie Rasterelektronenmikroskopie charakterisiert. Basierend auf diesen Untersuchungen lassen sich generelle Aussagen zur Lösemittelempfindlichkeiten organisch pigmentierter Ölfarben ableiten
The surface of an artwork is the interface to its environment and its viewer. The choice of a spe... more The surface of an artwork is the interface to its environment and its viewer. The choice of a specific behaviour and appearance by the artist is an essential part of the making and – of how we perceive the expression of the artist. Colour hue and intensity, reflectivity, surface structure, surface finishing and protection, etc. are elemental properties that are achieved with an often complex, multilayered and multicomponent system build-up of paintings or painted and varnished artwork. Chemical interaction between these components and layers, which age over time, influenced by environmental conditions, can lead to reactions that alter the visual impression and/or integrity of an artwork. Conservation science is thus confronted with alterations at different interfaces and levels such as for example the pigment–environment (e.g. Cato et al. 2017), pigment-binder (Fig. 1, Ferreira et al. 2015) and the varnish-environment (e.g. Soulier et al. 2012) interface. Contrary to the development of new materials, understanding and reconstructing the past is generally hampered by alterations through time, poor or lost documentation, the limited availability of sample material that is scarce and, in the case of e.g. paintings or musical instruments, is barely accessible due to the high value of the objects. Furthermore, the experimental nature of the artists leads to the situation where the analyst is confronted with non-standardised materials and unconventional working techniques, such as for example the “tempera” painting technique (e.g Zumbühl et al. 2014; Ferreira et al. 2015). The variety of painted substrates (paper, polymer, textile, leather, wood, metal, glass, rock, mortar…) also implies that we have to deal with a wide range of surface properties and interface behaviour. Generalised approaches thus end in casework when it comes to interpretation of analytical data. The lack of historic reference material may lead to experimental re-production according to ancient recipes, in the case of Guignet green unveiling temperature dependant surface behaviour of pigment particles and as such variable end products (Zumbühl et al. 2009). Our current strategy is minimally invasive, combines the complementary techniques of infrared imaging (ATR-FTIR-FPA), Raman spectroscopy and scanning electron microscopy (VP-SEM, SE/BSE/EDS), applied sequentially to micro-samples. This combination not only covers a wide range of materials, but also delivers morphological and 2D stratigraphic information from minimal amounts of sample material. Specific developments such as the methodology to derivatise interfering compounds prior to FTIR measurement have further helped to significantly increase the selectivity of infrared spectroscopy and reach a new level of information in reconstructing historic coatings (Zumbühl et al. 2017). Figure 1. a) ‚Portrait of a young girl’ by Filippo Franzoni (ca. 1888, oil on canvas). b) Close-up view of the surface showing ‚gold’ particles turning green. c-e) crosssection of metal particle showing alteration products from pigment-binder interaction. (Ferreira et al. 2015) Literature References Cato E. et al. (2017) J Raman Spectrosc 1-10. doi.org/10.1002/jrs.5256 Ferreira E. et al. (2015) Herit Sci 3(1): 1-11. doi.org/10.1186/s40494-015-0052-3 Ferreira E. et al. (2016) In: Beltinger K. & Nadolny J. (Eds) KUNSTmaterial 4, Archetype Pub., Zürich, 205-227. Soulier et al. (2012). Z Kunsttechnol Konserv 108-117. Zumbühl S. et al. (2009) Stud Conserv 54, 149-159. doi.org/10.1179/sic.2009.54.3.149 Zumbühl S. et al. (2014) Appl Spectrosc 68(4): 458-465. doi.org/10.1366/13-07280 Zumbühl, S. et al. (2017) Microchem J 134, 317-326. doi.org/10.1016/j.microc.2017.06.013 https://www.hkb.bfh.ch/en/campus/art-technological-laboratory
L'usage de métal réduit en poudre dans les métiers d'art est attesté dès le haut Moyen âg... more L'usage de métal réduit en poudre dans les métiers d'art est attesté dès le haut Moyen âge. C'est à l'ère du baroque tardif et du rococo que la poudre métallique a connu son apogée comme procédé de revêtement. Puis les artistes préromantiques et symbolistes ont découvert les possibilités picturales offertes par la poudre métallique.
During the examination of two 19th century oil paintings by Swiss artists, the Reading pastor (ca... more During the examination of two 19th century oil paintings by Swiss artists, the Reading pastor (ca. 1885) by Ferdinand Hodler (1853-1918) and Portrait of a young girl (ca. 1888) by Filippo Franzoni , it was observed that in particular locations, the surface had an unusually granular texture, given by the application of metallic particles and the presence of large translucent green agglomerates. In this paper we investigate the composition and origin of the metal particles and green agglomerates. A combination of bulk analysis (GC-MS and FTIR) and analytical microscopy techniques (X-ray tomographic microscopy, light microscopy, ATR-FTIR-FPA imaging and SEM-EDX) were used. It was concluded that the metal particles are composed of a lower quality brass (copper/zinc alloy) and ground from foil. The current appearance resulted from the reaction of the brass and its corrosion products with the fatty acids in the surrounding paint/varnish matrix. This has lead to the formation of agglomerates of zinc and copper carboxylates, the latter responsible for their green colour.
Cleaning strategies in restoration and conservation often involve the use of solvent mixtures, de... more Cleaning strategies in restoration and conservation often involve the use of solvent mixtures, despite the fact that the interaction between these and the objects under treatment is not always well known. Binary solvent mixtures behave nonideally; that is, the properties are not directly proportional or related to the mixing ratio. This fact contradicts the trivialized solubility charts, for example, the Teas chart, known and applied in practical restoration. The description of the dissolving action of binary systems therefore requires additional information such as the solvation and solubilization mechanisms involved. The effects of binary solvent mixtures on oil and alkyd paints were systematically investigated, with particular focus on the swelling action and leaching of binding media components. In total, 75 binary mixtures made from the solvents nhexane, toluene, chloroform, diethyl ether, acetone, and ethanol were experimentally applied to free paint films by immersion. The so...
Zwischgold (also part-gold in English) is a two-layered metal foil made of gold and silver that w... more Zwischgold (also part-gold in English) is a two-layered metal foil made of gold and silver that was historically applied to altarpieces, sculptures and panel paintings. It tends to oxidize quickly in air and therefore was usually applied with a protective varnish layer. The purpose of applying Zwischgold is an interesting topic in the research of art history and art technologies. The identification of Zwischgold helps to define its application areas and thus the purpose of its application. However, when the Zwischgold surface is still well preserved, it can be challenging to differentiate it from surfaces applied with gold foils. In this paper, we present a handheld XRF analyser, "Niton XL3t GOLDD+", for a qualitative identification of Zwischgold surfaces. Its performance has been evaluated through measurements of Zwischgold models and also a 15-century altar figure applied with Zwischgold. The identification of Zwischgold by the "Niton XL3t GOLDD+" has proven to...
Effective and responsible use of solvents is an important competence of a conservator/restorer. T... more Effective and responsible use of solvents is an important competence of a conservator/restorer. The goal to selectively remove components such as varnishes from the surface without affecting underlying paint is a common challenge in the field of restoration. The complexity of the processes of solvation and dissolution has given rise to several approaches by various groups to simplify solvent action and deliver some selection criteria to the restorer. In general, however, these approaches lack both a qualitative and quantitative description of the dissolution processes. In the context of practical conservation needs, knowledge of the rate of solvent action will decide the ability to control a conservation treatment. Since the kinetics of solvent action mainly depend on an entropy change in the dissolving process, a different approach is necessary to satisfy the demands of current conservation practice.
During the examination of two 19th century oil paintings by Swiss artists, the Reading pastor (ca... more During the examination of two 19th century oil paintings by Swiss artists, the Reading pastor (ca. 1885) by Ferdinand Hodler (1853–1918) and Portrait of a young girl (ca. 1888) by Filippo Franzoni (1857–1911), it was observed that in particular locations, the surface had an unusually granular texture, given by the application of metallic particles and the presence of large translucent green agglomerates. In this paper we investigate the composition and origin of the metal particles and green agglomerates. A combination of bulk analysis (GC–MS and FTIR) and analytical microscopy techniques (X-ray tomographic microscopy, light microscopy, ATR–FTIR–FPA imaging and SEM–EDX) were used. It was concluded that the metal particles are composed of a lower quality brass (copper/zinc alloy) and ground from foil. The current appearance resulted from the reaction of the brass and its corrosion products with the fatty acids in the surrounding paint/varnish matrix. This has lead to the formation of...
Augusto Giacometti’s painting The Circling of the Planets (1907; 268 × 218 cm) is in a highly fra... more Augusto Giacometti’s painting The Circling of the Planets (1907; 268 × 218 cm) is in a highly fragile state, suffering from widespread flaking paint. These flakes are very brittle and rigid; none of the usual consolidation techniques managed to achieve necessary ductility to secure lifting paint flakes. In the blue areas, both absorbent protein-oil (lean tempera), as well as non-absorbent oil-protein (tempera grassa) layers were revealed by FTIR analysis. Furthermore, numerous adhesive materials, like wax and PVAc from past conservation treatments, were detected. This paper discusses systematic experiments performed to develop a viscosity-adjusted consolidating filler to secure displaced paint flakes, without mobilising residues of old adhesives or penetrating the lean tempera paint. The properties were controlled to ensure high viscosity, minimal shrinkage, and no build-up of tensile stress, as this could be harmful to the fragile flakes. To apply such a consolidating filler precis...
Uploads
Papers by Nadim Scherrer
Originating from a diploma project at the Dresden University of Fine Arts (HfBK Dresden), Germany, adhesive meshes were further investigated within a research project at the Bern University of Applied Sciences in cooperation with APM Technica AG, both Switzerland, and the HfBK Dresden. The outcome was an improved production process, commercial availability of adhesive meshes, and widening the product range by investigating basic adhesive properties of methylcellulose meshes. This current contribution explored adhesive meshes made of Methocel™ A4C (400 mPa·s) and Methocel™ A15LV (15 mPa·s) with respect to material and adhesive properties in comparison to the physical behavior of BEVA® 371 films. Commercial adhesive meshes, mass-produced by APM Technica, were compared to self-made adhesive meshes, manufactured using a laser-cut silicone mold. Canvas specimens were bonded with adhesive meshes, activated using a standardized spraying technique for laboratory tests. Bonding properties were determined by lap shear tests according to DIN EN 1465 that was adapted to canvas specimens. The results show that adhesive strength varies depending on the amount of activation water and the viscosity of the methylcellulose. Commercial and self-made adhesive meshes show similar tendencies despite the different weight per unit area (grammage). Both manufacturing modalities resulted in similar trends in bond strength. Due to the overall lower grammage, self-made Methocel™ A4C adhesive meshes require smaller amounts of water for activation, whereas APMˈs adhesive meshes are capable of higher maximum adhesive bond strengths when activated sufficiently. In general, the bond strength of adhesive meshes made from medium-viscosity Methocel™ A4C increases with the amount of activation water and can be adjusted over a wide range from slight to very strong adhesion. A moderate amount of activation water of ≥200 g/m² results in high to very high bond strengths, which are equal to and even exceed those of BEVA® 371 films. Adhesive meshes made from the low-viscosity Methocel™ A15LV achieve lower bond strengths, yet require smaller amounts of water ≤200 g/m² for activation. A higher water input leads to dissolution of the mesh, to a deeper penetration of the glue into the canvas and finally to a decrease in bond strength. In conclusion, adhesive meshes made from Methocel™ A4C meet the requirements when canvas bonding needs to withstand high tensile stress, e.g. with strip lining. Methocel™ A15LV meshes are, on the other hand, particularly suited to attach smaller patches exposed to low or moderate stress. They proved suitable for poorly accessible bonding surfaces and water-sensitive materials where only a minimum of humidity is acceptable.
Originating from a diploma project at the Dresden University of Fine Arts (HfBK Dresden), Germany, adhesive meshes were further investigated within a research project at the Bern University of Applied Sciences in cooperation with APM Technica AG, both Switzerland, and the HfBK Dresden. The outcome was an improved production process, commercial availability of adhesive meshes, and widening the product range by investigating basic adhesive properties of methylcellulose meshes. This current contribution explored adhesive meshes made of Methocel™ A4C (400 mPa·s) and Methocel™ A15LV (15 mPa·s) with respect to material and adhesive properties in comparison to the physical behavior of BEVA® 371 films. Commercial adhesive meshes, mass-produced by APM Technica, were compared to self-made adhesive meshes, manufactured using a laser-cut silicone mold. Canvas specimens were bonded with adhesive meshes, activated using a standardized spraying technique for laboratory tests. Bonding properties were determined by lap shear tests according to DIN EN 1465 that was adapted to canvas specimens. The results show that adhesive strength varies depending on the amount of activation water and the viscosity of the methylcellulose. Commercial and self-made adhesive meshes show similar tendencies despite the different weight per unit area (grammage). Both manufacturing modalities resulted in similar trends in bond strength. Due to the overall lower grammage, self-made Methocel™ A4C adhesive meshes require smaller amounts of water for activation, whereas APMˈs adhesive meshes are capable of higher maximum adhesive bond strengths when activated sufficiently. In general, the bond strength of adhesive meshes made from medium-viscosity Methocel™ A4C increases with the amount of activation water and can be adjusted over a wide range from slight to very strong adhesion. A moderate amount of activation water of ≥200 g/m² results in high to very high bond strengths, which are equal to and even exceed those of BEVA® 371 films. Adhesive meshes made from the low-viscosity Methocel™ A15LV achieve lower bond strengths, yet require smaller amounts of water ≤200 g/m² for activation. A higher water input leads to dissolution of the mesh, to a deeper penetration of the glue into the canvas and finally to a decrease in bond strength. In conclusion, adhesive meshes made from Methocel™ A4C meet the requirements when canvas bonding needs to withstand high tensile stress, e.g. with strip lining. Methocel™ A15LV meshes are, on the other hand, particularly suited to attach smaller patches exposed to low or moderate stress. They proved suitable for poorly accessible bonding surfaces and water-sensitive materials where only a minimum of humidity is acceptable.