The discoloring interaction between the artist's pigments cadmium yellow and the copper-containing malachite, an interaction that is conjectured to cause black spotting in oil paintings of the 19th ...and early 20th centuries, was examined using X-ray mapping and scatter diagram analysis. The application of these coupled techniques confirmed that copper sulfide phases were produced during discoloration reaction. Scatter diagram analysis indicated that two copper sulfide stoichiometries (CuS and Cu3S2) were present as reaction products where previously only crystalline CuS (covellite) had been identified by X-ray diffraction. The results demonstrate the potential of X-ray mapping coupled with scatter diagram analysis for the identification of both crystalline and X-ray amorphous phases produced by such complex heterogeneous interactions and their applicability to the investigation of interactions of artists' pigments.
Naturally occurring minerals or their synthetic analogues have been important as pigments used in artistic and cosmetic contexts in global antiquity. The analysis and identification of mineral ...pigments, though routine to the petrologist or mineralogist, also requires specialist knowledge of the archaeological contexts and available technologies and trade. This paper attempts to present an analytical approach to the study of mineral pigments in archaeology and also introduces the range of mineral pigments encountered in works of art and painted objects on archaeological sites and in museums. It attempts to cover the range of mineral and synthetic inorganic pigments used in global cultures from to the early Medieval period.
A comprehensive study of the luminescence properties of cadmium pigments was undertaken to determine whether these properties could be used for in situ identification and mapping of the pigments in ...paintings. Cadmium pigments are semiconductors that show band edge luminescence in the visible range and deep trap luminescence in the red/infrared range. Emission maxima, quantum yields, and excitation spectra from the band edge and deep trap emissions were studied for sixty commercial cadmium pigments that span the color range from yellow to red (reflectance transition 470 to 660 nm). For paints containing cadmium pigments, luminescence from deep traps was more readily observable than that from the band edge, although the yield varied widely from zero to around 4.5%. Optimal excitation for emission is found to be in the visible for both pigments in powder form and mixed with a medium. The maxima of the deep trap emission shift with the band gap energy, providing a potentially useful way to assign pigment type even when used in pigment mixtures. The usefulness of the results of the study on mockups was demonstrated by the mapping of cadmium pigments of different hues with the aid of calibrated luminescence imaging spectroscopy in a painting by Edward Steichen, entitled Study for ‘Le Tournesol’ (1920). Analysis of the luminescence image cube reveals at least six unique spectral components, associated with emission from white pigments, paint binder, and cadmium red and yellow pigments. The results were compared with those from X-ray fluorescence spectrometry (XRF) and fiber-optic reflection spectroscopy (FORS) and the results obtained on paint samples containing cadmium pigments. These results show that, when present, the emission from traps can be used as an analytical tool to identify cadmium pigments, to distinguish among cadmium sulfide, cadmium zinc sulfide, and cadmium sulfoselenide, and to map cadmium pigments, even in mixtures.
The chemistry of making color in art Cartechini, Laura; Miliani, Costanza; Nodari, Luca ...
Journal of cultural heritage,
July-August 2021, 2021-07-00, Letnik:
50
Journal Article
Recenzirano
In this review, the main technological processes involved in the production of color in glasses, ceramics and pigments are reported. Iron (as oxides or dispersed ion) is the main responsible of the ...color in archeological and historical ceramics and glasses, but other d-metals can be also found (Cu, Ag, Co, Cr, Ni) as nano-particles or dispersed ions. The final coloration is usually a result of the sapient choice of raw materials and firing conditions (temperature, atmosphere).
Some pigments are chosen to represent the different, often sophisticated, chemical processes that have been used during the history to produce them: solid state reaction (Egyptian and Chinese Blue, Naples Yellow, Ultramarine Blue), host-guest complexation (Maya Blue), corrosion/redox processes (Lead White, Verdigris), wet/solution synthesis (Prussian Blue, Cadmium Yellow).
In addition, a brief overview on the vast production of modern compounds (inorganic and mostly organic) is given.
This review shows how behind the artistic choice and way of expression lies a high level of technological skill and chemical knowledge achieved/reached by (ancient) craftsmen to obtain the desired colors.
•11 fungal isolates from cultural heritage institutions’ interiors were screened for xerophilic trait.•Specially designed incubators were constructed to hold specific RH levels of 55%, 63% and ...74.%•Fungal growth was monitored at low relative humidity on wood and glass supports painted by traditional artists’ paints.•Effects of pigments, support materials and strain variability are discussed.
Even though contamination of painted artwork by xerophilic moulds frequently causes aesthetical, physical and/or biochemical biodeterioration, mould growth on paints, prepared from assorted traditional artists’ pigments, has yet to be systematically evaluated especially with regard to low relative humidity (RH) levels and painted support materials. Therefore, we investigated 11 fungal strains isolated mostly from cultural heritage institutions’ interiors for their potential to grow on egg tempera paint films prepared with different colouring agents and applied on wooden and glass supports which were maintained in monoculture in specially designed incubators at three different RH levels of 55%, 63% and 74%. The growth rate of mould over the surface was assessed using fluorescent microscopy after Calcofluor White staining. Additionally, these stains were screened for their xerophilic and hydrolytic potential using standard microbiological assays. Results show that when comparing growth rates on egg tempera paint films, 6 isolates grew exclusively on wood, exemplifying the greater susceptibility of this supporting material to mould attack. Prussian blue paint also stimulated the growth of 6 isolates, and the maximum overall expansion (38%) was observed on Prussian blue painted wood. RH was the key factor limiting growth, and at RH of 55% only a slight growth of 2 isolates was observed on Prussian blue painted wood. On the same samples incubated at RH of 63%, 10 isolates exhibited a moderate to strong growth and 4 of these showed an additional increase in growth at 74% RH. Paints consisting of artists’ pigments carmine lake or lead white in general completely prevented the development of moulds. Nevertheless, tolerance was species/strain dependant and the growths of isolates Cladosporium halotolerans EXF-15,333, Aspergillus niger EXF-14,897 and Aspergillus creber EXF-15,148 on lead white paint (containing ions and salts of heavy metal lead (Pb+2)) even exceeds 11%. Standard microbiological tests showed that all stains had hydrolytic potential and proved positive for xerophilic trait, nevertheless their ability to develop on egg tempera paint films was mostly dependant of very specific conditions.
•The first immunofluorescence microscopy attempt of targeting two different types of proteins on the same cultural heritage micro sample.•A two-step antibody hybridization procedure to analyse two ...different types of protein binders in real wall paintings.•This procedure allowed us to reduce the costs and operational difficulties, which are normally encountered, when mixing two types of primary antibodies.•Ovalbumin was found in 3 micro samples and casein in 1 micro sample; and none proved positive for both binder types.
The aim of the study was to use immunofluorescence microscopy to identify two types of protein binders in 10 polished cross sections of micro samples, which were obtained from real and mock-up wall paintings. A two-step antibody hybridisation procedure was employed, in which the same micro samples were hybridised with anti-ovalbumin and subsequently with anti-casein antibodies and between the hybridisation steps, the sample's cross section was slightly re-polished and cleaned in order to remove all primary and secondary antibody remnants, which remained attached from the first hybridisation step (anti-ovalbumin). This allowed us to reduce the costs and operational difficulties, which are normally encountered, when antibodies, targeting two different proteins, are simultaneously mixed together. To reduce unspecific fluorescence, to amplify the fluorescence of the proteinaceous binders and to construct 3D surface topography models, apart from widefield fluorescence, laser-scanning confocal microscopy was performed. In parallel, FTIR spectroscopy analysis, of finding proteinaceous materials in micro sample cross sections, was also conducted. Results show that our two-step hybridisation procedure allowed for an accurate localisation of both types of proteinaceous binders without any interference from the first hybridisation step. Three micro samples proved positive for ovalbumin and one for casein and none of these proved positive for both analysed binder types. For eight micro samples, FTIR spectroscopy results completely matched those of immunofluorescence microscopy. According to our knowledge, this was the first immunofluorescence microscopy attempt of targeting two different types of proteins on the same cultural heritage micro sample.
•Can pigments within a paint hinder proteinous binder characterization using immunofluorescence microscopy?.•Eight out of 10 tested pigments did not interfere with binder characterization using ...immunofluorescence microscopy.•Five pigments exhibited weak autofluorescence, which did not interfere with immunofluorescence microscopy.•Confocal fluorescence gave clearer results to widefield fluorescence.•Cross sections with smooth surfaces gave a much clearer immunofluorescence microscopy picture.
The aim of the study was to address the problematics of proteinous binder characterization, within a cross section of painted model samples, using immunofluorescence microscopy. Problems arise from certain pigments which can alter the epitope sites of target binders (lead white and verdigris) or can exhibit a strong natural autofluorescence (lake pigments). Therefore, dual layered model samples were prepared containing a lower egg tempera paint and an upper oil paint, and both paints were made of the same pigment. As an extra challenge for fluorescence microscopy, half of samples were additionally covered with pure linseed oil (as a third layer), which is known to physically reflect fluorescence. Cross-sections were hybridized with anti-ovalbumin antibodies and with FITC labelled secondary antibodies. To reduce unspecific fluorescence, apart from widefield fluorescence, laser-scanning confocal immunofluorescence microscopy was performed. Finally, 3D surface topography models were constructed which were used to check off any unspecific fluorescence originating from cracks or holes. Results show that immunofluorescence microscopy in the widefield observation mode was successful in its specificity and clarity of highlighting the egg paint layer in the presence of 8 out of 10 pigments, including the problematic lead white and verdigris pigments. Several of these pigments (lead white, malachite, yellow ochre, madder lake and carbon black) exhibited autofluorescence; however it was not bright enough to interfere with the successful immunofluorescence microscopy result. In the widefield mode, immunofluorescence microscopy was unsuccessful in the presence of 2 pigments; carmine lake (pigment adsorbs antibodies) and Dragon's blood (pigment dissolved during resin curing at 50 °C). The confocal observation mode in comparison to the widefield mode achieved a much more specific and clear immunofluorescence microscopy picture (especially in the presence of Prussian blue, Vermilion and carbon black) and removed nearly all of the unspecific fluorescence originating from resin's surface reflection, from pure oil binder, from small indentations and from illumination glair that would have otherwise spread across different layers. Lastly, 3D topography models showed that in general samples with smooth surfaces gave a much clearer immunofluorescence microscopy picture.
Shift of Raman peaks of the artists’ pigment α-copper phthalocyanine to higher wavenumbers (red spectrum) with increasing pressure in a diamond-anvil cell.
•Use of diamond-anvil cell micro-Raman ...spectroscopy in a forensic art study.•Easy distinction between the α- and β-copper phthalocyanine polymorphs.•The α-polymorph does not exhibit any structural changes.•The β-polymorph exhibits a reversible phase transition at 2.0GPa.
The two polymorphs of copper phthalocyanine, α- and β-CuPc, have been examined by micro-Raman spectroscopy at pressures approaching 5.0GPa. The metastable α-polymorph does not exhibit any structural changes, while the more thermodynamically stable β-polymorph does exhibit a reversible phase transition at 2.0GPa. The pressure dependences (dν/dP) for a selected number of vibrational modes are reported. Two regions of the Raman spectra, 800–900cm−1 and 1100–1200cm−1, are sensitive to pressure such that they can be used as indicators of the polymorphic form.
While the most famous historical green earth deposits in Italy and Cyprus were exceptionally rich in celadonite, the deposits near Kadaň, Czech Republic, consisted of thin Fe‐rich celadonite ...impregnations accompanied by interstratified celadonite/smectite. In superimposed tuffs, smectites become prevalent and their colour changes from forest to olive green. Powder X‐ray microdiffraction and infrared microspectroscopy permit us to distinguish between green earth minerals in microsamples taken from works of art. The Ti contents and the Fe/Mg ratios help to indicate the presence of Bohemian green earth from Kadaň. We found this material in local 18th‐century works of art and also in paintings by Anton Kern (1709–47).
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