Kate Helwig
Canadian Conservation Institute, Conservation Science Division, Department Member
- Kate Helwig earned an honours B.Sc. in Chemistry from the University of Toronto, a Master’s degree in Physical Chemis... moreKate Helwig earned an honours B.Sc. in Chemistry from the University of Toronto, a Master’s degree in Physical Chemistry from Stanford University in California and a Master’s Degree in Art Conservation from Queen’s Univeristy, Kingston. Since 1992, she has worked at the Canadian Conservation Institute where she is a Senior Conservation Scientist. She specializes in the analysis of art and archeological materials using Fourier transform infrared spectroscopy, Raman spectroscopy and light microscopy. Her research interests include: history and characterization of artists’ pigments; materials and techniques of Canadian painters; study of residues on archaeological artifacts; and efflorescence and soap formation in modern oil paints. She has published numerous articles in peer-reviewed journals and contributed a chapter on the iron oxide pigments to the fourth volume of the Artists’ Pigments series, published by the National Gallery in Washington. She is also a co-author of Jean Paul Riopelle: the Artist's Materials, the second book in the Artists’ Materials series published by the Getty Conservation Institute. She was an editor for the CCI symposium post prints Preserving Aboriginal Heritage, Technical and Traditional Approaches, Ottawa, Canada, September 24-28, 2007. She was also co-editor of the Canadian Association for Conservation (CAC) Bulletin from 2001 to 2004, has been an associate editor for the Journal of the CAC since 2003, and acted as co-editor of the Journal from 2008-2010.edit
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Water triggers crystallization of zinc soaps in polymer networks, especially when water is mixed with polar organic solvents. This finding has a big impact on conservation of oil paintings.
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The fluorescence from disordered phenanthrene adlayers on Al2O3(0001) was examined in ultrahigh vacuum at 20 K using laser-induced fluorescence techniques. The fluorescence spectra was consistent with emission from a phenanthrene excimer.... more
The fluorescence from disordered phenanthrene adlayers on Al2O3(0001) was examined in ultrahigh vacuum at 20 K using laser-induced fluorescence techniques. The fluorescence spectra was consistent with emission from a phenanthrene excimer. The fluorescence lifetime of the phenanthrene excimer was studied versus phenanthrene coverage and versus distance from the Al2O3(0001) surface using xenon spacers. As a function of coverage on Al2O3(0001), the fluorescence lifetime decreased from τ=34±0.5 ns at phenanthrene coverages of Θ≥20 ML to τ=7±0.5 ns at Θ=1 ML. As a function of xenon spacer distance from the Al2O3(0001) surface, the fluorescence lifetime also decreased from τ=34±0.5 ns at distances of d>100 Å to τ=7±0.5 ns at d=7 Å. Fluorescence measurements versus phenanthrene coverage on xenon, butane, acetonitrile and methanol multilayers revealed that the phenanthrene excimer fluorescence lifetime was constant at τ≊35 ns on the molecular multilayer surfaces. These results indicated that the reduction of the fluorescence lifetime was particular to the Al2O3(0001) surface. The fluorescence lifetimes versus phenanthrene coverage and xenon spacer distance on Al2O3(0001) were equivalent when the phenanthrene coverage was converted to total adlayer thickness. This correspondence suggested that the excited electronic energy in disordered phenanthrene adlayers transfers rapidly to phenanthrene excimers at the phenanthrene–vacuum interface. Subsequently, competition occurs between fluorescence quenching by the Al2O3(0001) surface and phenanthrene excimer fluorescence. In addition, fluorescence lifetime measurements vs phenanthrene coverage on CaF2 thin films displayed similar fluorescence quenching. Fluorescence lifetimes versus phenanthrene coverage on O2 molecular multilayers also revealed fluorescence quenching that was attributed to a charge-transfer mechanism. The observed fluorescence quenching on Al2O3(0001) indicates that the surface states of this ionic crystal may be accessible for electronic energy transfer even though Al2O3 is a known insulator. A Förster electronic energy transfer mechanism was used to analyze the observed fluorescence lifetimes vs phenanthrene coverage or xenon spacer distance on Al2O3(0001).
Research Interests: Engineering, Chemistry, Photochemistry, Fluorescence, Chemical Physics, and 12 moreFluorescence Lifetime, Thin Film, Physical sciences, Laser Induced Fluorescence, CHEMICAL SCIENCES, Surface Properties, Low Temperature, Energy Transfer, Phenanthrene, Charge transfer, Excimer, and Fluorescence quenching
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The new högbomite-group mineral magnesiohögbomite-6N12S, ideally Mg5Al11TiO23(OH), was found in calcite “vein-dikes” at the DeWitts Corners occurrence, lots 10 and 11, concession 1, Bathurst Township, Ontario, Canada. It forms tabular and... more
The new högbomite-group mineral magnesiohögbomite-6N12S, ideally Mg5Al11TiO23(OH), was found in calcite “vein-dikes” at the DeWitts Corners occurrence, lots 10 and 11, concession 1, Bathurst Township, Ontario, Canada. It forms tabular and short-prismatic crystals up to 5 mm in size. The major forms are pinacoid {0001} and hexagonal pyramid {11${\bar 2}$1}, sometimes modified by hexagonal prism {11${\bar 2}$0}. The associated minerals are magnesiohögbomite-2N3S, spinel, corundum, diopside, magnesio-hastingsite, pargasite, clinochlore and calcite. Magnesiohögbomite-6N12S is dark brown to black with brown streak and vitreous lustre. It has no cleavage and its fracture is uneven. The Mohs hardness is 6½. Dcalc is 3.87 g/cm3. The infrared spectrum is reported. The composition (wt.%) is MgO 13.09, ZnO 0.46, FeO 11.91, Fe2O3 6.84, Al2O3 62.70, TiO2 4.44, H2O 0.99, total 100.43. The empirical formula calculated on the basis of 17 cations, excluding H+, is (Mg2.95Fe2+1.51Al0.49Zn0.05)Σ5(Al10...
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Alex Janvier is a prolific painter who played a key role in the development of contemporary Indigenous art in Canada. While his works are generally in very good condition, the large-scale, oil on canvas painting Womenizer is an exception.... more
Alex Janvier is a prolific painter who played a key role in the development of contemporary Indigenous art in Canada. While his works are generally in very good condition, the large-scale, oil on canvas painting Womenizer is an exception. Although the painting initially appeared to dry normally, areas of the work are now tacky, and some paint has become almost liquid. This article describes the painting’s history, conservation issues, and a detailed analysis of the paint. Pigments and fillers were identified with a combination of FTIR, SEM/EDX, Raman, PLM and XRD. The overall composition of the drying oil was studied with FTIR and Py-GCMS. In addition, extraction of pre-weighed samples using a silylating reagent followed by GCMS allowed the composition and relative quantity of the non-crosslinked fraction of the oil to be determined. While the overall Py-GCMS results were typical for a young oil paint film and similar for all samples, the GCMS results for the non-cross-linked fracti...
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Abstract Alpine ice patches were caribou and sheep hunting territories for southern Yukon First Nations people for thousands of years. With increasing global temperatures, well-preserved projectile weapons that were frozen for centuries... more
Abstract Alpine ice patches were caribou and sheep hunting territories for southern Yukon First Nations people for thousands of years. With increasing global temperatures, well-preserved projectile weapons that were frozen for centuries are now melting out of the ice. The study of organic residues on recovered projectiles is part of a larger effort to learn about traditional hunting technology. Here we identify the residue on a recently recovered, 6000-year-old throwing dart as castoreum, harvested from the castor sacs of butchered beavers. FTIR spectroscopy and pyrolysis-GC-MS analysis of the residue indicated substituted phenols, phenolic dimers, coumarins and xanthenes as well as cholesterol derivatives and traces of protein. Comparative analysis of reference material extracted from the castor sacs of recently trapped beavers confirmed the identity of the residue as castoreum. This finding represents the earliest evidence of castoreum use in the fabrication of weaponry and the first chemical identification of this material in the archaeological record.
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A new arrojadite-group mineral manganoarrojadite-(KNa), ideally KNa5MnFe13Al(PO4)11(PO3OH)(OH)2, was found in a phosphate-bearing granite pegmatite at the Palermo No. 1 mine, New Hampshire, USA. It forms anhedral grains up to 1 × 1.5 cm... more
A new arrojadite-group mineral manganoarrojadite-(KNa), ideally KNa5MnFe13Al(PO4)11(PO3OH)(OH)2, was found in a phosphate-bearing granite pegmatite at the Palermo No. 1 mine, New Hampshire, USA. It forms anhedral grains up to 1 × 1.5 cm in size combined in aggregates with vivianite, goyazite, quartz and calcite. The mineral is olive green with a pale green streak and vitreous to greasy lustre. The cleavage is good in one direction. The Mohs hardness is 4½. Dcalc is 3.53 g/cm3. Manganoarrojadite-(KNa) is optically biaxial (–), α = 1.658(2), β = 1.666(2), γ = 1.670(2), 2Vmeas. = 67(1)° and 2Vcalc. = 70° (589 nm). The infrared spectrum is reported. The composition (wt.%) is Na2O 6.97, K2O 1.78, CaO 0.31, MgO 2.17, MnO 12.30, FeO 31.17, Al2O3 2.43, P2O5 40.48, F 0.30, H2O 1.32, O = F2 –0.13, total 99.10. The empirical formula calculated on the basis of 12 P and (O+OH+F) = 50 apfu is Na4.73K0.80Ca0.12Mg1.13Mn2+3.65Fe2+9.13Al1.00P12.00O46.59OH3.08F0.33. The ideal structural formula is A1K...
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ABSTRACT Class Ib resinites are the most common subclass of amber and are found throughout the world. They have a macromolecular structure based on co-polymerized communic acid, communol and biformenes. Because this class of resinite does... more
ABSTRACT Class Ib resinites are the most common subclass of amber and are found throughout the world. They have a macromolecular structure based on co-polymerized communic acid, communol and biformenes. Because this class of resinite does not contain succinic acid, crosslinking of the polymer through esterification of communol moieties has never been theorized. Analysis of Class Ib resinites from Grassy Lake and Cedar Lake in western Canada was performed using pyrolysis-gas chromatography-mass spectrometry with in situ hexamethyldisilazane derivatization, using a thermal separation probe to perform the pyrolysis and sample introduction. This has allowed larger, more complex fragments to be released from the polymer matrix than previously possible using instantaneous pyrolysis methodologies. The results show for the first time that Class Ib resinite can undergo self-crosslinking between the communol and communic acid moieties in the polylabdane matrix. The chromatographic results also show that a portion of the monoterpenes and non-polymerizable diterpenes in the resinite are bound to the polymer matrix and not fully occluded as was previously theorized. Fourier transform infrared (FTIR) spectra of the resinites are presented and a more accurate spectral interpretation is proposed, based on the chromatographic results.
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In an on-going study of the materials and techniques of twentieth-century Canadian painters, similar conservation issues in oil paintings by various artists have been noted. These include delamination and lifting paint, zinc soap... more
In an on-going study of the materials and techniques of twentieth-century Canadian painters, similar conservation issues in oil paintings by various artists have been noted. These include delamination and lifting paint, zinc soap protrusions and surface efflorescence or accretions. Examples of these phenomena are presented. Delamination in an oil painting from 1956 was found to be related to an underlayer with a high concentration of zinc fatty acid salts (zinc soaps). In two paintings that date from 1936 and 1937, zinc soaps have aggregated and formed protrusions that have broken through the paint surface. The protrusions were analysed using a combination of SEM-EDX, GCMS and FTIR. The FTIR spectra were compared to those of synthetic zinc palmitate, stearate, azelate and oleate. The combined GCMS and FTIR results indicate that the protrusions contain primarily zinc palmitate and stearate. Peak splitting in the FTIR spectrum, which is not observed in synthetic zinc palmitate, stearate or binary palmitate-stearate salts, is likely due to structural distortion. The final example describes a disfiguring surface accretion on a 1952–1954 painting caused by the reaction of zinc with a low molecular weight carboxylic acid (2-hydroxypropanoic or lactic acid).
Research Interests: Chemistry, Painting, FTIR spectroscopy, Painting Conservation, Science for Conservation and Restoration of Cultural Heritage, and 9 moreGC-MS, Zinc, Paint Analysis, Fourier transform infrared spectroscopy, Micro-Raman and FTIR spectroscopy, FTIR SPECTROSCOPY CULTURAL HERITAGE, Stearic Acid, Efflorescence, and Springer Ebooks
Research Interests: Archaeology, Materials Science, Art, Painting, FTIR spectroscopy, and 9 moreVisual Arts, Painting Conservation, Science for Conservation and Restoration of Cultural Heritage, GC-MS, Mixed Media Artwork, Fourier transform infrared spectroscopy, FTIR SPECTROSCOPY CULTURAL HERITAGE, Turpentine, and Alkyd
Non-invasive techniques are being increasingly used for the study of heritage objects. This article describes the results of pigment analysis on a fragmentary Egyptian sculpture using two non-invasive infrared methods: external... more
Non-invasive techniques are being increasingly used for the study of heritage objects. This article describes the results of pigment analysis on a fragmentary Egyptian sculpture using two non-invasive infrared methods: external reflectance Fourier-transform infrared (ER-FTIR) spectroscopy and visible-induced infrared luminescence (VIL) photography. ER-FTIR spectroscopy was used to identify certain of the pigments used on the sculpture, including Egyptian blue, in variously coloured areas. An optimized VIL photographic technique, using a high-resolution camera combined with focus-stacking, permitted detailed mapping of the location of Egyptian blue on the sculpture, including sub-millimeter grains of the pigment scattered across the object’s surface, which were not visible to the naked eye.
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ABSTRACT This article describes a study of adhesive residues on 16 projectile weapons, 15 from ice patches in southwest Yukon and one from the Selwyn Mountains, Northwest Territories. The objects selected for analysis cover much of the... more
ABSTRACT This article describes a study of adhesive residues on 16 projectile weapons, 15 from ice patches in southwest Yukon and one from the Selwyn Mountains, Northwest Territories. The objects selected for analysis cover much of the Holocene, with radiocarbon dates from 8103 to 170 cal. yr. BP and represent both throwing-dart and bow-and-arrow technology. The goal of the study was to identify the residues associated with hafting and to determine if patterns of material use exist. The residues were analyzed using a combination of analytical techniques: Fourier transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GC-MS), Raman spectroscopy, scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) and polarized light microscopy (PLM). Hafting adhesive residues were found on nine objects that relate to throwing-dart technology and on two objects related to bow-and-arrow technology. In all cases where adhesive was found, the projectiles included chipped stone components. All adhesives, regardless of age, were found to be conifer resin, more specifically identified as spruce (Picea sp.). While the majority of adhesives were relatively pure, homogeneous spruce resin, in the case of three stone dart points, the spruce resin was intentionally mixed with red ochre to produce a compound adhesive. A fourth stone dart point showed the use of spruce “callus” resin, a type of resin produced during wound closure on the surface of the tree, which has a unique chemical signature.
Research Interests: Archaeology, Geology, Geochemistry, Archaeological Science, FTIR spectroscopy, and 13 moreArchaeometry, Alpine Archaeology, Science for Conservation and Restoration of Cultural Heritage, GC-MS, Lithic Projectile Hafting system, Ice Patch Archaeology, Natural resin, White spruce resin adhesive, Late Glacial Archaeology, Arctic and Subarctic hunter-gatherers, Red Ochre, Archeology, and Hafting Adhesives
The Kwäday Dän Ts'inchi Discovery project is one of two confirmed projects within the IPY Activity #435 titled "Recovery Research and Stabilization of Culturally and Scientifically Significant Specimens From Melting Ice and... more
The Kwäday Dän Ts'inchi Discovery project is one of two confirmed projects within the IPY Activity #435 titled "Recovery Research and Stabilization of Culturally and Scientifically Significant Specimens From Melting Ice and Cryosols." This activity involves science and social science research that has been initiated as a result of the recent melting of glaciers and alpine ice patches. Melting of these scientific "deep freezes" is providing unanticipated data sources that are giving us insight into past northern societies, flora/fauna, environments, and their changes through time. The field work is occurring in different northern Canadian jurisdictions (both Yukon/B.C. and Nunavut), and is operating under the leadership of northern governments (territorial or state) and/or First Nations government representatives. Local communities are directly involved in the projects, directing and/or participating in the fieldwork. They are also intimately involved in the s...
Two case studies of calcium fatty acid salts in oil paint are presented. The first is a nineteenth-century oil on canvas painting, and the second is a decoratively painted ceiling. In both cases, the calcium soaps have formed in the lower... more
Two case studies of calcium fatty acid salts in oil paint are presented. The first is a nineteenth-century oil on canvas painting, and the second is a decoratively painted ceiling. In both cases, the calcium soaps have formed in the lower layers of the paint systems and are associated with significant delamination and paint loss. The results of analysis of samples from the two works using FTIR, SEM-EDX, Raman, PLM, and Py-GC-MS are presented. The components of the paint and ground involved in the soap formation, the conditions that may have led to their formation, and the treatment strategies that were chosen are described.
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The formation of crystalline zinc soaps (zinc salts of fatty acids) in oil paint layers is a common sign of paint degradation. In this study, we have used infrared spectroscopy to systematically identify differences in structure and... more
The formation of crystalline zinc soaps (zinc salts of fatty acids) in oil paint layers is a common sign of paint degradation. In this study, we have used infrared spectroscopy to systematically identify differences in structure and composition of crystalline zinc soap phases, and report data analysis methods for structure attribution in challenging oil paint samples. Supported by reported crystal structures, it was possible to distinguish two distinct types of zinc soap geometry: a highly symmetrical packing for long-chain saturated soaps (type B) and an alternating packing for zinc soaps with short, unsaturated, or dicarboxylic chains (type A). These two types of packing can be identified by a single or split asymmetric COO stretch vibration band. With this new information, we studied the structure and composition of zinc soaps formed in a zinc white model paint and in a cross-section from the painting Equations in Space by Lawren Harris. Using non-negative matrix factorization, b...
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Alpine ice patches were caribou and sheep hunting territories for southern Yukon First Nations people for thousands of years. With increasing global temperatures, well-preserved projectile weapons that were frozen for centuries are now... more
Alpine ice patches were caribou and sheep hunting territories for southern Yukon First Nations people for thousands of years. With increasing global temperatures, well-preserved projectile weapons that were frozen for centuries are now melting out of the ice. The study of organic residues on recovered projectiles is part of a larger effort to learn about traditional hunting technology. Here we identify the residue on a recently recovered, 6000-year-old throwing dart as castoreum, harvested from the castor sacs of butchered beavers. FTIR spectroscopy and pyrolysis-GC-MS analysis of the residue indicated substituted phenols, phenolic dimers, coumarins and xanthenes as well as cholesterol derivatives and traces of protein. Comparative analysis of reference material extracted from the castor sacs of recently trapped beavers confirmed the identity of the residue as castoreum. This finding represents the earliest evidence of castoreum use in the fabrication of weaponry and the first chemi...
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ABSTRACT Shortly after a major renovation at the Royal Ontario Museum, it was noticed that the glass panels in many of the new display cases exhibited fogging or hazing on the surface, sometimes in very specific patterns. Cleaning removed... more
ABSTRACT Shortly after a major renovation at the Royal Ontario Museum, it was noticed that the glass panels in many of the new display cases exhibited fogging or hazing on the surface, sometimes in very specific patterns. Cleaning removed the fogging temporarily, but it began to reappear within 12 months. An investigation of fogged glass panels in display cases was undertaken to understand the source of the fogging and to develop an appropriate cleaning method. This included the analysis of residues from glass panels in several galleries, and surface imaging and compositional analysis of glass panels. The fogging residues on the glass panels consist mainly of sodium salts of organic acids and inorganic anions. Sources of the sodium in the residues include air particulate matter and the glass itself. The organic acids and inorganic anions that form salts with the sodium cations likely originate from volatile organic compounds (VOCs) and particulate matter in the air. Examination of the fogging patterns on the glass panels revealed that the sodium salts grow on marks made during cleaning attempts and the manufacturing process. These cleaning and manufacturing marks contain greasy residues that encourage crystal growth. Because of the variation in surface cleanliness, panels with more cleaning and manufacturing residues appear to be heavily fogged while those with less may appear to be unfogged in the museum display cases. A cleaning protocol was tested on two of the glass panels, and was found to remove all traces of grease and fogging residue. GRAPHICAL ABSTRACT
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Paintings and painted objects are quite susceptible to degradation, as paint layers are usually composed of complex mixtures of materials that can participate in chemical degradation processes. The identification of the constituent... more
Paintings and painted objects are quite susceptible to degradation, as paint layers are usually composed of complex mixtures of materials that can participate in chemical degradation processes. The identification of the constituent materials in paint (including binders, pigments, and fillers) and the degradation products within paint layers is of particular importance to ensuring the conservation of paintings, by providing important information both about their material history as well as their state of conservation. Metal fatty acid salts (metal soaps) are degradation products that can form in situ from interactions between inorganic pigments and free fatty acids in oil-based binding media, and can cause significant condition issues in paintings. Fourier transform infrared (FTIR) spectroscopy is one of the leading analytical techniques for the study of metal soaps. In this article, the materials analysis of several cross-sections from paintings and painted objects from works in Can...
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ABSTRACT This paper describes an investigation into the causes of specific degradation phenomena in three oil paintings from the 1960s by eminent Indigenous Canadian painter Rita Letendre. A comprehensive technical study of the paintings... more
ABSTRACT This paper describes an investigation into the causes of specific degradation phenomena in three oil paintings from the 1960s by eminent Indigenous Canadian painter Rita Letendre. A comprehensive technical study of the paintings was undertaken using a combination of SEM-EDS, FTIR spectroscopy, Py-GC-MS, Raman spectroscopy, XRD, and polarised light microscopy to determine pigments, fillers, additives, paint medium, and degradation products. Compositional factors, including high abundances of manufacturers’ additives such as aluminum stearate and castor wax, have likely contributed to the formation of oil exudates and fatty acid efflorescence. Cross sections illustrated an inhomogeneous distribution of additives and incomplete mixing of components in some colours. This appears to be due to the migration of components over time and also to Letendre’s technique, which included application of thick paint directly from the tube and the addition of extra medium to some impastos. Cracking, lifting, and protrusions in several areas were caused by the crystallization of zinc soaps below the paint surface. FTIR mapping allowed the spatial distribution of crystalline and ionomeric-type zinc soaps to be determined within a problematic paint layer.
Research Interests: Archaeology and Art
Chemical and microscopical analyses were undertaken of samples from the rock painting sites Azcona (El Bolsón) in Río Negro Province and Campo Moncado 1 (Valle de Piedra Parada) and Cerro Pintado (Cholila) in Chubut Province, Argentina,... more
Chemical and microscopical analyses were undertaken of samples from the rock painting sites Azcona (El Bolsón) in Río Negro Province and Campo Moncado 1 (Valle de Piedra Parada) and Cerro Pintado (Cholila) in Chubut Province, Argentina, by the Canadian Conservation Institute. Representative microsamples were removed from rock paintings and substrate rock to investigate the pigments and any mineral accretions present. Analysis by x-ray microanalysis (scanning electron microscopy) and x-ray microdiffraction revealed the presence of hematite, lepidocrocite, and green earth (celadonite or glauconite) pigments as well as calcium oxalates (whewellite structure). (AATA Nos: 2006-108423 and 40-2592; Abstractor: Ian N.M. Wainwright)
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ABSTRACT This article describes the investigation of white efflorescence on eight wooden African objects from Malawi and Zambia and the treatment of the objects to remove the deposits. The source of the efflorescence on these objects was... more
ABSTRACT This article describes the investigation of white efflorescence on eight wooden African objects from Malawi and Zambia and the treatment of the objects to remove the deposits. The source of the efflorescence on these objects was determined to be the heartwood from which they were carved. Using gas chromatography-mass spectrometry and Fourier transform infrared spectrometry, the crystalline efflorescence was found to consist of homopterocarpin and pterocarpin, two isoflavonoid compounds found in woods and shrubs belonging to the genus Pterocarpus, and African Baphida nitida. The crystal growth appeared to be heaviest on areas of the objects that were more deeply carved as well as on those objects without a surface finish. The storage conditions of the collection were studied and found to have likely accelerated the rate and extent of the natural movement of the pterocarpan compounds from the interior of the heartwood to the outer surfaces.
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Abstract In an on-going study of the materials and techniques of twentieth-century Canadian painters, similar conservation issues in oil paintings by various artists have been noted. These include delamination and lifting paint, zinc soap... more
Abstract In an on-going study of the materials and techniques of twentieth-century Canadian painters, similar conservation issues in oil paintings by various artists have been noted. These include delamination and lifting paint, zinc soap protrusions and surface efflorescence or accretions. Examples of these phenomena are presented. Delamination in an oil painting from 1956 was found to be related to an underlayer with a high concentration of zinc fatty acid salts (zinc soaps). In two paintings that date from 1936 and 1937, zinc soaps have aggregated and formed protrusions that have broken through the paint surface. The protrusions were analysed using a combination of SEM-EDX, GCMS and FTIR. The FTIR spectra were compared to those of synthetic zinc palmitate, stearate, azelate and oleate. The combined GCMS and FTIR results indicate that the protrusions contain primarily zinc palmitate and stearate. Peak splitting in the FTIR spectrum, which is not observed in synthetic zinc palmitate, stearate or binary palmitate-stearate salts, is likely due to structural distortion. The final example describes a disfiguring surface accretion on a 1952–1954 painting caused by the reaction of zinc with a low molecular weight carboxylic acid (2-hydroxypropanoic or lactic acid).
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This article describes a study of adhesive residues on 16 projectile weapons, 15 from ice patches in southwest Yukon and one from the Selwyn Mountains, Northwest Territories. The objects selected for analysis cover much of the Holocene,... more
This article describes a study of adhesive residues on 16 projectile weapons, 15 from ice patches in southwest Yukon and one from the Selwyn Mountains, Northwest Territories. The objects selected for analysis cover much of the Holocene, with radiocarbon dates from 8103 to 170 cal. yr. BP and represent both throwing-dart and bow-and-arrow technology. The goal of the study was to identify the residues associated with hafting and to determine if patterns of material use exist. The residues were analyzed using a combination of analytical techniques: Fourier transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GC-MS), Raman spectroscopy, scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) and polarized light microscopy (PLM). Hafting adhesive residues were found on nine objects that relate to throwing-dart technology and on two objects related to bow-and-arrow technology. In all cases where adhesive was found, the projectiles included chipped stone components. All adhesives, regardless of age, were found to be conifer resin, more specifically identified as spruce (Picea sp.). While the majority of adhesives were relatively pure, homogeneous spruce resin, in the case of three stone dart points, the spruce resin was intentionally mixed with red ochre to produce a compound adhesive. A fourth stone dart point showed the use of spruce “callus” resin, a type of resin produced during wound closure on the surface of the tree, which has a unique chemical signature.
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Describes the identification of a hafting adhesive on an antler point slotted for microblade insertion. The adhesive, found in the slots of the point, would have held the microblades in place. Radiocarbon dated to 7310 ± 40 BP... more
Describes the identification of a hafting adhesive on an antler point slotted for microblade insertion. The adhesive, found in the slots of the point, would have held the microblades in place. Radiocarbon dated to 7310 ± 40 BP (uncalibrated), the point is one of the oldest and best-preserved artifacts recovered from the melting alpine ice patches in southwestern Yukon, Canada. Because the artifact was frozen, the organic components have not degraded, and a detailed chemical analysis was possible. Analyses of residue in the slots of the point by Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry showed that a conifer resin adhesive was used. The high concentration of diterpene resin acids with an abietane or pimerane skeleton confirmed a Pinaceae source for the resin. There were no chemical markers to indicate that the resin had been strongly heated to produce tar or pitch. Based on a comparison with five Pinaceae resins from trees common to southern Yukon, the resin from the slotted point most closely resembles the chemical profile of spruce (Picea sp.).
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This paper describes a new sub-category of Class I resinites based on labdanoid diterpenes having an enantiomeric configuration, including ozic acid, ozol and enantio biformenes, and incorporating succinic acid. This hitherto unnamed... more
This paper describes a new sub-category of Class I resinites based on labdanoid diterpenes having an enantiomeric configuration, including ozic acid, ozol and enantio biformenes, and incorporating succinic acid. This hitherto unnamed resinite sub-class, now designated as Class Id, has been identified in three distinct deposits in Canada: two sites in Nunavut and one site in British Columbia. The composition of Class Id resinites was determined using pyrolysis-gas-chromatography-mass spectrometry with in situ trimethylsilylation with hexamethyldisilazane, Py(HDMS)-GC-MS. Fourier transform infrared spectroscopy (FTIR) of the resinites was also carried out and provided evidence of partial esterification of the ozol with succinic acid.
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This paper describes the examination and analysis of four mixed media paintings from the 1960s and 1970s by Canadian artist Jack Chambers (1931-1978). The documentary evidence about his materials and methods is summarized and compared to... more
This paper describes the examination and analysis of four mixed media paintings from the 1960s and 1970s by Canadian artist Jack Chambers (1931-1978). The documentary evidence about his materials and methods is summarized and compared to the results of analysis of multilayer paint samples. The combination of FTIR and GC-MS allowed the components of paint media to be characterized: ortho-phthalate alkyd resins, iso-phthalate alkyd resins, drying oils, dammar, Pinaceae resin and turpentine were identified in varying proportions. Many pigments and fillers were identified by FTIR and Raman and are enumerated. The effect that Chambers’ complex technique has had on the aging and degradation of the paintings is discussed. The severe cracking of the paint layers in one of the four paintings may be the result of a high proportion of dammar and turpentine diluent mixed with the alkyd paint and may also be related to the type of alkyd resin medium. Different history and environmental conditions may also be factors.
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The red iron oxide pigment known as burnt yellow earth has been used as a substitute for naturally occurring red earth since earliest times. Documentary evidence indicates that this pigment was often produced by heating yellow earth from... more
The red iron oxide pigment known as burnt yellow earth has been used as a substitute for naturally occurring red earth since earliest times. Documentary evidence indicates that this pigment was often produced by heating yellow earth from a few minutes to several hours at temperatures below 800°C. When yellow earth is burnt under these conditions, its constituent goethite is transformed to red iron oxide with an anomalous diffraction pattern corresponding to a disordered hematite crystal structure. Using pigments of known origin and processing, it is shown that x-ray microdiffractometry can be used to classify very small samples of red iron oxide pigments and that, in some cases, the diffraction pattern can provide evidence to support or refute the use of burnt yellow earth.
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Close Document Image Close Document Printer Image Print This Document! Conservation Information Network (BCIN). Author: Helwig, Kate Title Article/Chapter: "Mars colours: preparation methods and chemical composition ...
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"Jean Paul Riopelle (1923–2002) was one of the most important Canadian artists of the twentieth century, yet he is relatively unknown in the U.S. He began his career in Montreal in the 1940s, where he played a role in the influential... more
"Jean Paul Riopelle (1923–2002) was one of the most important Canadian artists of the twentieth century, yet he is relatively unknown in the U.S. He began his career in Montreal in the 1940s, where he played a role in the influential Automatist movement, and established his reputation in the burgeoning art scene of postwar Paris, where his circle included André Breton, Samuel Beckett, and Sam Francis. During his career, Riopelle produced over six thousand works, including more than two thousand paintings.
This volume, the second in the Artist’s Materials series, grew out of a research project of the Canadian Conservation Institute. Initial chapters present an overview of Riopelle’s life and situate his work within the context of twentieth century art. Subsequent chapters address Riopelle’s materials and techniques, focusing on his oil paintings and mixed media works, and on conservation issues. The preface is by Yseult Riopelle, the artist’s eldest daughter and editor of his catalogue raisonné. This first book-length study of the artist in English will interest curators, conservators, conservation scientists, and general readers."
This volume, the second in the Artist’s Materials series, grew out of a research project of the Canadian Conservation Institute. Initial chapters present an overview of Riopelle’s life and situate his work within the context of twentieth century art. Subsequent chapters address Riopelle’s materials and techniques, focusing on his oil paintings and mixed media works, and on conservation issues. The preface is by Yseult Riopelle, the artist’s eldest daughter and editor of his catalogue raisonné. This first book-length study of the artist in English will interest curators, conservators, conservation scientists, and general readers."
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A retrospective exhibition of Yves Gaucher's work was recently organized by the Musée d'art contemporain de Montréal. This exhibition, which opened .in 2003, was the starting point for a research project on the studio painting materials... more
A retrospective exhibition of Yves Gaucher's work was recently organized by the Musée d'art contemporain de Montréal. This exhibition, which opened .in 2003, was the starting point for a research project on the studio painting materials of the artist. The three main aspects of the project were: to gather documentary information about the artist's technique, to develop a database of the materials found in his studio, and to analyze selected paint materials from the studio to determine their chemical composition. A total of 375 samples was taken from the studio, documented in a database, and archived for future use. Analysis of 36 of the purest materials was undertaken using scanning electron microscopy combined with energy dispersive spectroscopy (SEM-EDX), Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), and polarized light microscopy (PLM). The documentation and analysis provided information about the working methods and materials of the artist. Gaucher used a wide range of modern materials; three different types of acrylic media and a large number of pigments were identified. The pigments included organic compounds such as naphthol reds, Hansa yellows, and phthalocyanine green, among others. Inorganic materials included pigments such as cadmium reds and yellows, iron oxides, and ultramarine blue, as well as an unusual extender, nepheline syenite, a sodium potassium aluminum silicate.
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Close Document Image Close Document Printer Image Print This Document! Conservation Information Network (BCIN). Author: Corbeil, Marie-Claude; Helwig, Kate; Poulin, Jennifer Title Article/Chapter: "Une étude scientifique... more
Close Document Image Close Document Printer Image Print This Document! Conservation Information Network (BCIN). Author: Corbeil, Marie-Claude; Helwig, Kate; Poulin, Jennifer Title Article/Chapter: "Une étude scientifique ...
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Describes the scientific analysis of the original materials of an 18th-century japanned long case clock from the collection of the Royal British Columbia Museum in Victoria, British Columbia. Analysis showed that the wood was prepared... more
Describes the scientific analysis of the original materials of an 18th-century japanned long case clock from the collection of the Royal British Columbia Museum in Victoria, British Columbia. Analysis showed that the wood was prepared with a thick gesso layer composed of calcium carbonate (chalk) in a protein medium. This white ground was followed with a single application of an opaque, light blue layer pigmented with indigo, lead white, and calcium carbonate, also in a protein medium. The colored japanned layers, applied on top of the light blue layer, are composed of translucent layers of smalt in a natural resin medium, followed by layers of unpigmented natural resin. In both the colored japanned layers and the unpigmented layers, the natural resin was found to be from a tree source rather than shellac. Raised decoration was produced with a paste of calcium carbonate mixed in a drying oil medium applied to the surface and then sealed with natural resin. Examination of selected surface decorations showed the use of gold leaf, powdered brass, and powdered tin, all applied to a mordant pigmented with vermilion. Pigments employed for the painted decoration included iron oxide pigments, carbon black, and vermilion. The materials identified on the clock are compared to those described in historic treatises on japanning.
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The role of David Alfaro Siqueiros (1896-1974) and his use of pyroxyline-based paints are crucial in the transition from oil to acrylic paints. During the early 20th century, his experimentation with this innovative paint medium had a... more
The role of David Alfaro Siqueiros (1896-1974) and his use of pyroxyline-based paints are crucial in the transition from oil to acrylic paints. During the early 20th century, his experimentation with this innovative paint medium had a great impact on North American traditional painting ...
Describes the examination of an early scientific instrument known as the Christian Island "astrolabe." Its discovery in the 1920s in the ruins of Fort Ste. Marie II, near Penetang, Ontario, links the astrolabe with the Jesuit missionaries... more
Describes the examination of an early scientific instrument known as the Christian Island "astrolabe." Its discovery in the 1920s in the ruins of Fort Ste. Marie II, near Penetang, Ontario, links the astrolabe with the Jesuit missionaries who spent the 1649-50 winter there. While it is not a true astrolabe, it is engraved with many of the scales found on such instruments. The metal was found to be a copper alloy whose composition is consistent with historic "brasses" and is very brittle. An x-radiograph suggested the presence of lead or tin solder along one of the cracks. A clumsy repair composed of shellac mixed with talc and brass flakes was not removed because of the fragility of the surrounding metal. Corrosion products, identified as malachite and cuprite, were well attached and generally stable. The existing glass mounting system keeps the fragile metal flat and stable; its historical quality also argues for retention of the mount. While the glass may hinder visibility somewhat, this problem is offset by the availability of photographic and descriptive material produced during the examination.
Focuses on specific aspects of the technique of Canadian abstract painter, Jean-Paul Riopelle. Riopelle's early works were painted in oil. He painted thickly and mixed matte and lustrous paint. This technique has resulted in several... more
Focuses on specific aspects of the technique of Canadian abstract painter, Jean-Paul Riopelle. Riopelle's early works were painted in oil. He painted thickly and mixed matte and lustrous paint. This technique has resulted in several conservation problems, such as the cracking of matte paint and the appearance of exudates. The same pigment/oil combinations were found in samples of damaged blue paint and of blue paint that showed no defects. Analysis confirmed that the exudate is oil that has leached out from the paint: linseed or poppy-seed oil, or mixtures of these two drying oils. One consequence of Riopelle's use of matte and glossy paint is that his paintings should never be varnished. In the 1980s, Riopelle started using more nontraditional materials, including aerosol paint and paint for crafts and fabrics, which introduced a new set of conservation concerns for his work. Two types of aerosol paint were identified, one based on an isophthalate alkyd, the other containing a melamine-formaldehyde-sulfonamide resin, which acts as a carrier for fluorescent pigments. The same medium, consisting of an acrylic ester-acrylonitrile-styrene copolymer, was found in most of the nonaerosol paint samples, including nacreous paints based on ironoxide-mica pigments. (See also AATA 38-1907 and 41-4016.)
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Technical examination of an oil painting on canvas attributed to Louis Dulongpré has provided insight into the nature of the ground layer responsible for the poor condition of the work. The paint and ground layers exhibited extensive... more
Technical examination of an oil painting on canvas attributed to Louis Dulongpré has provided insight into the nature of the ground layer responsible for the poor condition of the work. The paint and ground layers exhibited extensive cracking, cleavage, cupping, and loss throughout. Cross sections from several areas of the painting were examined, and components were identified using a combination of x-ray microanalysis, x-ray diffraction, Fourier transform infrared spectroscopy, and polarized light microscopy. The examination showed that three distinct ground layers were applied to the canvas before the portrait was painted. Cross sections and x-radiographs provided evidence that these ground layers had cracked even before the application of the paint layers. The first ground layer applied to the canvas was found to be composed of starch, protein, gypsum, and a red iron oxide pigment. The presence of a high concentration of starch granules in this layer indicated that the material was not heated sufficiently to form a paste. This explains the lack of cohesion within the ground layer and the ensuing cracking and cleavage. Although the use of pigmented, starch-based preparatory layers is mentioned in documentary sources, this type of ground has rarely been identified in a painting.