Two case studies of calcium fatty acid salts in oil paint are presented. The first is a nineteent... 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.
Non-invasive techniques are being increasingly used for the study of heritage objects. This artic... 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.
The Kwäday Dän Ts'inchi Discovery project is one of two confirmed projects within the IPY Act... 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...
Alex Janvier is a prolific painter who played a key role in the development of contemporary Indig... 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...
The formation of crystalline zinc soaps (zinc salts of fatty acids) in oil paint layers is a comm... 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...
A new arrojadite-group mineral manganoarrojadite-(KNa), ideally KNa5MnFe13Al(PO4)11(PO3OH)(OH)2, ... 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...
Paintings and painted objects are quite susceptible to degradation, as paint layers are usually c... 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...
This article describes the identification of a hafting adhesive on an antler point, slotted for m... more This article 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 B.P. (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 ...
The ammonium, NHâ/sup +/, and tetrammineplatinum (II), (Pt(NHâ)â)/sup 2 +/, cation vibrational mo... more The ammonium, NHâ/sup +/, and tetrammineplatinum (II), (Pt(NHâ)â)/sup 2 +/, cation vibrational modes in self-supporting wafers of (NHâ)Na-Y and (Pt(NHâ)â)Na-Y have been directly probed by in situ Fourier transform far-infrared (FT-far-IR) spectroscopy in the 300-30-cmâ»Â¹ range. These ..cap alpha..-cage cations are found to absorb in the far-IR region at room temperature, around 169 and 42 cmâ»Â¹, respectively. By subjecting these
Probing Extra-Framework Cations in Alkali-and Alkaline-Earth-Metal Linde Type A ... Zeolites by F... more Probing Extra-Framework Cations in Alkali-and Alkaline-Earth-Metal Linde Type A ... Zeolites by Fourier Transform Far-Infrared Spectroscopy ... Mark D. Baker,? John Godber,: Kate Helwig,s and Geoffrey A. Ozin* ... Lash Miller Chemical Laboratories, Department of ...
Close Document Image Close Document Printer Image Print This Document! Conservation Information N... more 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 ...
For years, the recovery of amber beads and other objects with amber components from archaeologica... more For years, the recovery of amber beads and other objects with amber components from archaeological sites in Canada has raised questions concerning the deposit site sources for this highly traded material. Objects found at one site may have originated elsewhere, thus, the accurate characterisation of amber could aid in establishing trade. In this investigation, 12 distinct amber specimens from 11 deposit sites in Canada were studied in order to determine their subclass and other distinguishing chemical features. The ambers were analysed using Fourier transform infrared spectrometry (FTIR) in combination with pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS), using a thermal separation probe (TSP) to perform the pyrolysis and sample introduction. Analysis of the amber from the 11 deposits in Canada showed that they represent three different classes: Class Ib (based on regular-labdanes), Class Ic and Class Id (both based on enantio-labdanes). Different forms were found within the Class Ib and Ic ambers, based on the presence and absence of self-crosslinking and free succinic acid. The techniques identified polymeric crosslinking in three subclasses. These include self-crosslinking of communol and communic acid moieties in two Class Ib (form 2) ambers, self-crosslinking of ozol and ozic acid moieties in one Class Ic (form 2) amber and succinylation of the Class Id ambers. Other important characteristics were discovered, including the presence of free succinic acid in six Class Ib (form 1) ambers and one Class Ic (form 1) amber, the presence of diagenetic analogues of both dehydroabietic acid and callitrisic acid in all Class Ib (form 1) ambers, and the attachment of non-polymerisable terpenoids to the macromolecular structures of two Class Ib ambers and one Class Id amber. Amber beads recovered from three Thule sites in the Canadian arctic were characterised and compared to the 12 reference specimens. The beads from site TkAu-1 (Ellesmere Island) were found to originate from the local deposit at Lake Hazen. However, beads from the QeJu-1 (Cornwallis Island) and OkRn-1 (Banks Island) sites closely matched amber specimens from the major deposit at Cedar Lake (Manitoba). This may indicate movement of the Cedar Lake amber to the arctic via trade.
ABSTRACT Class Ib resinites are the most common subclass of amber and are found throughout the wo... 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.
The role of David Alfaro Siqueiros (1896-1974) and his use of pyroxyline-based paints are crucial... 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 ...
Close Document Image Close Document Printer Image Print This Document! Conservation Information N... more Close Document Image Close Document Printer Image Print This Document! Conservation Information Network (BCIN). Author: Corbeil, Marie-Claude; Helwig, Kate; Poulin, Jennifer Editor: Roy, Ashok; Smith, Perry Title Article ...
Abstract In an on-going study of the materials and techniques of twentieth-century Canadian paint... 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).
... Registry No. C6H50H, 108-95-2; Rh, 7440-16-6; C6H50, 2122-46-5; co, 630-08-0; "C... more ... Registry No. C6H50H, 108-95-2; Rh, 7440-16-6; C6H50, 2122-46-5; co, 630-08-0; "C6H5OH, 89059-34-7. Diffusion of Ethylene and Xenon in Thin Pyrazine Layers Douglas Blue: Kate Helwig,t and Martin Moskovits* Department ...
Two case studies of calcium fatty acid salts in oil paint are presented. The first is a nineteent... 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.
Non-invasive techniques are being increasingly used for the study of heritage objects. This artic... 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.
The Kwäday Dän Ts'inchi Discovery project is one of two confirmed projects within the IPY Act... 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...
Alex Janvier is a prolific painter who played a key role in the development of contemporary Indig... 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...
The formation of crystalline zinc soaps (zinc salts of fatty acids) in oil paint layers is a comm... 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...
A new arrojadite-group mineral manganoarrojadite-(KNa), ideally KNa5MnFe13Al(PO4)11(PO3OH)(OH)2, ... 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...
Paintings and painted objects are quite susceptible to degradation, as paint layers are usually c... 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...
This article describes the identification of a hafting adhesive on an antler point, slotted for m... more This article 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 B.P. (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 ...
The ammonium, NHâ/sup +/, and tetrammineplatinum (II), (Pt(NHâ)â)/sup 2 +/, cation vibrational mo... more The ammonium, NHâ/sup +/, and tetrammineplatinum (II), (Pt(NHâ)â)/sup 2 +/, cation vibrational modes in self-supporting wafers of (NHâ)Na-Y and (Pt(NHâ)â)Na-Y have been directly probed by in situ Fourier transform far-infrared (FT-far-IR) spectroscopy in the 300-30-cmâ»Â¹ range. These ..cap alpha..-cage cations are found to absorb in the far-IR region at room temperature, around 169 and 42 cmâ»Â¹, respectively. By subjecting these
Probing Extra-Framework Cations in Alkali-and Alkaline-Earth-Metal Linde Type A ... Zeolites by F... more Probing Extra-Framework Cations in Alkali-and Alkaline-Earth-Metal Linde Type A ... Zeolites by Fourier Transform Far-Infrared Spectroscopy ... Mark D. Baker,? John Godber,: Kate Helwig,s and Geoffrey A. Ozin* ... Lash Miller Chemical Laboratories, Department of ...
Close Document Image Close Document Printer Image Print This Document! Conservation Information N... more 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 ...
For years, the recovery of amber beads and other objects with amber components from archaeologica... more For years, the recovery of amber beads and other objects with amber components from archaeological sites in Canada has raised questions concerning the deposit site sources for this highly traded material. Objects found at one site may have originated elsewhere, thus, the accurate characterisation of amber could aid in establishing trade. In this investigation, 12 distinct amber specimens from 11 deposit sites in Canada were studied in order to determine their subclass and other distinguishing chemical features. The ambers were analysed using Fourier transform infrared spectrometry (FTIR) in combination with pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS), using a thermal separation probe (TSP) to perform the pyrolysis and sample introduction. Analysis of the amber from the 11 deposits in Canada showed that they represent three different classes: Class Ib (based on regular-labdanes), Class Ic and Class Id (both based on enantio-labdanes). Different forms were found within the Class Ib and Ic ambers, based on the presence and absence of self-crosslinking and free succinic acid. The techniques identified polymeric crosslinking in three subclasses. These include self-crosslinking of communol and communic acid moieties in two Class Ib (form 2) ambers, self-crosslinking of ozol and ozic acid moieties in one Class Ic (form 2) amber and succinylation of the Class Id ambers. Other important characteristics were discovered, including the presence of free succinic acid in six Class Ib (form 1) ambers and one Class Ic (form 1) amber, the presence of diagenetic analogues of both dehydroabietic acid and callitrisic acid in all Class Ib (form 1) ambers, and the attachment of non-polymerisable terpenoids to the macromolecular structures of two Class Ib ambers and one Class Id amber. Amber beads recovered from three Thule sites in the Canadian arctic were characterised and compared to the 12 reference specimens. The beads from site TkAu-1 (Ellesmere Island) were found to originate from the local deposit at Lake Hazen. However, beads from the QeJu-1 (Cornwallis Island) and OkRn-1 (Banks Island) sites closely matched amber specimens from the major deposit at Cedar Lake (Manitoba). This may indicate movement of the Cedar Lake amber to the arctic via trade.
ABSTRACT Class Ib resinites are the most common subclass of amber and are found throughout the wo... 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.
The role of David Alfaro Siqueiros (1896-1974) and his use of pyroxyline-based paints are crucial... 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 ...
Close Document Image Close Document Printer Image Print This Document! Conservation Information N... more Close Document Image Close Document Printer Image Print This Document! Conservation Information Network (BCIN). Author: Corbeil, Marie-Claude; Helwig, Kate; Poulin, Jennifer Editor: Roy, Ashok; Smith, Perry Title Article ...
Abstract In an on-going study of the materials and techniques of twentieth-century Canadian paint... 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).
... Registry No. C6H50H, 108-95-2; Rh, 7440-16-6; C6H50, 2122-46-5; co, 630-08-0; "C... more ... Registry No. C6H50H, 108-95-2; Rh, 7440-16-6; C6H50, 2122-46-5; co, 630-08-0; "C6H5OH, 89059-34-7. Diffusion of Ethylene and Xenon in Thin Pyrazine Layers Douglas Blue: Kate Helwig,t and Martin Moskovits* Department ...
Uploads
Papers by Kate Helwig