Abstract
Fires can have a negative impact on the environment, human health, property and ultimately also on various objects of cultural heritage (CH). This paper deals with an investigation into the ...degradation of selected proteinaceous paint layers that were exposed to fire-related effects (i.e., fire effluents and/or high temperatures) in a modified cone-calorimeter system. Paint layers of egg yolk adhesive (E) and lead white tempera (E + LW) were exposed to fire-related impacts on top of a CH stack and in a specially designed CH test chamber. On the CH stack, the proteinaceous paint layers were exposed to fire effluents and high temperatures, while in the CH test chamber, the samples were exposed mainly to fire effluents. The molecular changes to the exposed paint layers were analysed by invasive and non-invasive spectroscopic analyses (i.e., FTIR and Raman spectroscopy) and complimented with pyrolysis-GC–MS, while the colour changes were evaluated using colourimetry. It was concluded that the proteinaceous binder degrades into aromatic amino acids and/or fatty acids after exposure to the overall impacts of the fire. Aromatic amino acids were detected by means of the FTIR and py-GC–MS analyses. In the case of the lead white tempera exposure, partial dissociation of the lead white pigment was confirmed by the detection of alteration products, such as lead oxide and lead carbonate. Moreover, the investigation of the E + LW samples exposed for longer times revealed the presence of lead carboxylates. On the other hand, no significant molecular changes were observed with the CH samples exposed to fire effluents in the CH test chamber. The research offered us an insight into the fire-induced effects on selected paints for the first time.
Raman spectral references for various formulations of iron gall inks, logwood inks and mixtures of both types were acquired during this study. The samples, either liquid or dry inks and applied on ...paper, were analysed using a portable Raman spectrometer, both with 852 and 785 nm excitation lines, and a confocal dispersive Raman microscope with two different excitations, namely 785 and 532 nm. It was found that longer wavelengths are more suitable for the analysis of iron gall inks and that the spectral response of logwood inks is relatively more dependent on the excitation line. For the mixtures, it is suggested analyses be performed with both longer and shorter wavelengths, since with a 785 nm line mainly the characteristic features of the metal-polyphenol complex in iron gall inks are detected, while the spectra collected with a 532 nm excitation contain information on the presence of logwood inks. The study was complemented by non-invasive reflectance infrared spectroscopy, which enabled the detection of tannic acid in iron gall inks and in the mixtures, and by micro-Fourier transform infrared (FTIR) spectroscopy to complement the reference set. The study aims to contribute to the development of non-invasive protocols for identification of inks in historic and artistic works on paper, such as manuscripts and drawings.
Graphical Abstract
Literature research revealed that scientific work on the characteristics of historical decorative laminates (DLs), like typology, and particularly the material-technical aspects related to the ...composition and build-up is scarce in the field of conservation-restoration of modern materials. This paper aims to take the first step towards filling in this knowledge gap by demonstrating that an in-depth literature research and complementary chemical-physical analytical techniques are useful in characterising and contextualising historic decorative laminates. This research focused on gaining additional information within chemical analyses on material-technical insights. This could serve as a basis for a more comprehensive historical context. Several historical samples from different sample-catalogues and museum objects, spanning a period from 1953 to 1993, were collected and their respective cross-sections were characterised with infrared (mapping), FT-Raman, and dispersive micro-Raman spectroscopy. The different layers, such as the protective, decorative, and core layers were investigated, and materials such as melamine formaldehyde, urea formaldehyde, cellulose, lignin, titanium dioxide (rutile), zinc sulphide, synthetic organic pigments PR112 (monoazo pigment, Naphthol AS), and PG8 (azo metal complex, Pigment Green B) were detected.
Graphical Abstract
In this study, a painted beehive panel from the collection of the Slovene Ethnographic Museum was examined with respect to its material composition with the aim to reveal the painting technique. Due ...to the state of degradation due to outdoor weathering (UV irradiation, rainfall, extreme temperature and humidity fluctuations), as well as past conservation interventions, the object represented a complex analytical challenge. We aimed for non-invasive techniques (FTIR in reflection mode, Raman spectroscopy and hyperspectral imaging in the range of 400–2500 nm); however, in order to explore paint layers, cross-sections were also analysed using Raman spectroscopy. FTIR spectroscopy in transmission mode and gas chromatography coupled to mass spectrometry were also used on sample fragments. Various original materials were identified such as pigments and binders. The surface coating applied during conservation interventions was also characterised. Additionally, organic compounds were found (oxalate, carboxylate), representing transformation products. The potential use of Prussian blue as a background paint layer is discussed.
In this work, we showed the potential of photoreduced surface‐enhanced Raman spectroscopy or surface‐enhanced Raman scattering (SERS) substrate for the detection of organic colourants (in mixtures) ...in lipid and proteinaceous paint layers. Different organic colourants such as madder lake pigment, cochineal lake pigment and lac dye were included in the study. SERS procedure with different approaches was tested, namely, direct application, soaking (incubation) of the sample in the substrate and hydrolysis with the hydrofluoric (HF) acid vapours. For the analysis of colourants bound in linseed oil, a pretreatment step was required (soaking/incubating or hydrolysing with HF). Moreover, exposing a cross‐section of a sample taken from a polychrome work of art to the vapours of HF enabled SERS detection of the cochineal lake pigment in the paint layer of this cross‐section. Therefore, the SERS substrate could be used also for the study of stratigraphy of real cultural heritage samples. As the analyses by means of SERS are (minimally) invasive, the potential of noninvasive reflection FTIR‐spectroscopy analyses for the identification of organic colourants was tested as well. Reflection infrared spectra of organic colourants are presented and discussed. Furthermore, within this study, it was shown that madder lake pigment could be identified in paint layers based on the characteristic bands of the hydrated alumina.
The potential of photoreduced SERS substrate for the detection of the organic colourants (in mixtures) in lipid and proteinaceous paint layers is presented. Three different organic colourants and the cross‐section of the sample from a polychrome work of art were included in the study. As the analyses by means of SERS are (minimally) invasive, the potential of noninvasive reflection FTIR analyses for the identification of organic colourants was tested as well.
Identification of organic dyes together with possible degradation products is often complicated in the field of cultural heritage. The main focus of this work is utilization and comparison between ...non-invasive reflection infrared spectroscopy, transmission infrared spectroscopy, and surface-enhanced Raman spectroscopy (SERS), a minimally invasive technique in order to understand the ageing behaviour of paint layers containing organic dye alizarin carmine (alizarin red S, sodium alizarin sulfonate, ARS) in lipid and proteinaceous binder. The results obtained with both Fourier transform infrared (FTIR) spectroscopies highlight a significant degradation of ARS paint layers where changes in hydroxyl, sulfonate, and carbonyl groups of alizarin red S were observed. In most of the cases, the intensity of IR bands belonging to the degraded alizarin red S was so weak or shifted that would make its positive identification questionable in an unknown sample. After all, it was apparent that SERS is a powerful technique to detect even the trace ARS molecules. Furthermore, degradation was even more pronounced for the paint layers of ARS combined with linseed oil. Namely, a transparent white layer of sodium sulfate was formed above the aged ARS glaze layer.
•Degradation of alizarin carmine paint layers (different binders)•Detection of Na2SO4 in a transparent layer present on the surface of the aged paint layer•Non-invasive reflection FTIR spectroscopy complemented with SERS
•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.
•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 primary purpose of the study, as part of the planned conservation work, was to uncover all aspects of autochthonous biofilm pertaining to the formation of numerous deterioration symptoms ...occurring on the limestone Rožanec Mithraeum monument in Slovenia. Using state-of-the-art sequencing technologies combining mycobiome data with observations made via numerous light and spectroscopic (FTIR and Raman) microscopy analyses pointed out to epilithic lichen
Gyalecta jenensis
and its photobiont, carotenoid-rich
Trentepohlia aurea
, as the origin of salmon-hued pigmented alterations of limestone surface. Furthermore, the development of the main deterioration symptom on the monument, i.e., biopitting, was instigated by the formation of typical endolithic thalli and ascomata of representative Verrucariaceae family (
Verrucaria
sp.) in conjunction with the oxalic acid-mediated dissolution of limestone. The domination of lichenized fungi, as the main deterioration agents, both on the relief and surrounding limestone, was additionally supported by the high relative abundance of
lichenized
and
symbiotroph
groups in FUNGuild analysis. Obtained results not only upgraded knowledge of this frequently occurring but often overlooked group of extremophilic stone heritage deteriogens but also provided a necessary groundwork for the development of efficient biocontrol formulation applicable in situ for the preservation of similarly affected limestone monuments.
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