Aloe plants have been widely documented in artists’ treatises dating from the sixteenth to the ni... more Aloe plants have been widely documented in artists’ treatises dating from the sixteenth to the nineteenth century as a source of colorant to achieve lustrous golden glazes on tin- and silver-foiled objects and warm-toned finishes on musical instruments, such as violins. Aloe extracts contain characteristic anthraquinone and phenolic components which impart a distinctive orange tone and fluorescence to mixtures containing them. Because of the low concentration of colorant in the coatings and its probable degradation by high temperature during manufacture, the identification of aloe in heated oil–resin mixtures represents an analytical challenge. For this reason, the possible presence of aloe in glazes and coatings has been largely overlooked. This paper describes various analytical approaches to the identification of aloe in historic samples, from comparison with results obtained from reference standards and mock-up samples. Complementary analytical techniques including thermally assisted hydrolysis and methylation–gas chromatography–mass spectrometry, high-performance liquid chromatography, laser desorption–mass spectrometry, matrix-assisted laser desorption-ionization-mass spectrometry and surface-enhanced Raman scattering were used. Different chemical markers were identified by the individual methods and the advantages and limitations of each technique for the identification of aloe in oil–resin varnishes are discussed.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
As a non-invasive or micro-invasive technique attenuated total reflectance Fourier transform infr... more As a non-invasive or micro-invasive technique attenuated total reflectance Fourier transform infrared spectroscopic (ATR-FTIR) microscopy is a valuable tool for the analysis of materials in works of art. An application for which it has received growing interest is in the analysis of paint cross-sections. However, FTIR microscope configurations, objectives’ geometries and low spatial resolutions, and issues of sample preparation have often hampered the characterization of individual layers or features in cross-sections. With the use of case studies, it is demonstrated here that an ATR-FTIR microscope featuring a crystal of optimized geometry and a viewing capability feature allows characterization of individual layers, or areas within layers, of 10 μm thickness or less in single measurements. Of particular value is a remote aperturing feature which allows the analysis of selected areas within the contact footprint of the ATR crystal. Since the technique is non-destructive, the same area can be analyzed by complementary microscopic techniques such as Raman spectroscopy and scanning electron microscopy with energy-dispersive spectroscopy. Pyrolysis gas chromatography-mass spectrometry was also used in some cases to corroborate the spectroscopic data. The analyses presented provided data which were important in informing art historical interpretation and conservation of the artworks examined. Figure Paint cross section from an 18th century American armchair painted white and selectively gilded. The original surface finish is characterized by trough and peaks from brush marks with accumulation of surface dirt. ATR-FTIR micro-spectroscopy performed on areas of the original and restoration layers allowed clear differentiation in medium and pigment distribution in visually similar white paint applications.
Aloe plants have been widely documented in artists’ treatises dating from the sixteenth to the ni... more Aloe plants have been widely documented in artists’ treatises dating from the sixteenth to the nineteenth century as a source of colorant to achieve lustrous golden glazes on tin- and silver-foiled objects and warm-toned finishes on musical instruments, such as violins. Aloe extracts contain characteristic anthraquinone and phenolic components which impart a distinctive orange tone and fluorescence to mixtures containing them. Because of the low concentration of colorant in the coatings and its probable degradation by high temperature during manufacture, the identification of aloe in heated oil–resin mixtures represents an analytical challenge. For this reason, the possible presence of aloe in glazes and coatings has been largely overlooked. This paper describes various analytical approaches to the identification of aloe in historic samples, from comparison with results obtained from reference standards and mock-up samples. Complementary analytical techniques including thermally assisted hydrolysis and methylation–gas chromatography–mass spectrometry, high-performance liquid chromatography, laser desorption–mass spectrometry, matrix-assisted laser desorption-ionization-mass spectrometry and surface-enhanced Raman scattering were used. Different chemical markers were identified by the individual methods and the advantages and limitations of each technique for the identification of aloe in oil–resin varnishes are discussed.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
As a non-invasive or micro-invasive technique attenuated total reflectance Fourier transform infr... more As a non-invasive or micro-invasive technique attenuated total reflectance Fourier transform infrared spectroscopic (ATR-FTIR) microscopy is a valuable tool for the analysis of materials in works of art. An application for which it has received growing interest is in the analysis of paint cross-sections. However, FTIR microscope configurations, objectives’ geometries and low spatial resolutions, and issues of sample preparation have often hampered the characterization of individual layers or features in cross-sections. With the use of case studies, it is demonstrated here that an ATR-FTIR microscope featuring a crystal of optimized geometry and a viewing capability feature allows characterization of individual layers, or areas within layers, of 10 μm thickness or less in single measurements. Of particular value is a remote aperturing feature which allows the analysis of selected areas within the contact footprint of the ATR crystal. Since the technique is non-destructive, the same area can be analyzed by complementary microscopic techniques such as Raman spectroscopy and scanning electron microscopy with energy-dispersive spectroscopy. Pyrolysis gas chromatography-mass spectrometry was also used in some cases to corroborate the spectroscopic data. The analyses presented provided data which were important in informing art historical interpretation and conservation of the artworks examined. Figure Paint cross section from an 18th century American armchair painted white and selectively gilded. The original surface finish is characterized by trough and peaks from brush marks with accumulation of surface dirt. ATR-FTIR micro-spectroscopy performed on areas of the original and restoration layers allowed clear differentiation in medium and pigment distribution in visually similar white paint applications.
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