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(A) FIR spectra of polyethylene (PE) coated with a thin film of water (W) recorded in the FIR region of 650–50 cm 1 . PE has one broad band at 540 cm 1 and one relatively sharp band at 73 cm 1 . All other bands can be attributed to water. (B) Cross-section of a PE pellet containing 0.6 mg of the pigment terra di Sienna (burnt). The cross-section shows homogeneous distribution of the pigment in the polyethylene. No air bubbles are visible and the PE pellet has a homogeneous thickness of approximately 1.0 mm (Optical Microscopy, original magnification 50x).
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Few research studies from the early seventies reported the use of far infrared (FIR) spectroscopy and its analytical potential. Especially in the field of cultural heritage, particular attention has not been given to this technique because of its destructive character; however, this can be overcome by employing Raman microscopy. Provided that enoug...
Contexts in source publication
Context 1
... FIR spectra of PE coated with a thin film of water is shown in Fig. 1(A). PE has one noticeable band at approximately 73 cm 1 and another weak and broad one at 540 cm 1 , which is usually covered by other bands coming from the pigment samples. Another band, whose origin is unknown (coming from the instrument, water or air), is at around 50 cm 1 , however, this band is not always present in the FIR spectra. ...
Context 2
... band at approximately 73 cm 1 and another weak and broad one at 540 cm 1 , which is usually covered by other bands coming from the pigment samples. Another band, whose origin is unknown (coming from the instrument, water or air), is at around 50 cm 1 , however, this band is not always present in the FIR spectra. The remaining bands seen in Fig. 1(A) can be attributed to water, which is present on this PE pellet as a thin film. Both water and PE bands have an intensity of less than 20% transmission and are therefore usually covered by actual pigment bands when PE pellets are mixed with a pigment. Figure 1(B) shows the cross-section of a PE pellet containing 0.6 mg of the standard ...
Context 3
... water and PE bands have an intensity of less than 20% transmission and are therefore usually covered by actual pigment bands when PE pellets are mixed with a pigment. Figure 1(B) shows the cross-section of a PE pellet containing 0.6 mg of the standard Kremer pigment terra di Sienna (burnt). The PE pellet has a diameter of 13 mm and a homogeneous thickness over the entire cross- section of approximately 1.05-1.08 ...
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Citations
... Except for breccia typical for Mass absorption coefficients of critical lunar minerals with characteristics similar to sulfides and ilmenites grouped into (A) oxyhydroxides (Stimson and O'Donnell, 1952 and JHU spectral library: https://speclib.jpl.nasa.gov/documents/jhu_desc; Salisbury et al., 1989;Murad and Bishop, 2000;Kendix et al., 2008) with values multiplied by 0.5 (hematite) and 2 (akaganeite) for clarity, (B) secondary rock-forming silicates (Stimson and O'Donnell, 1952 and JHU spectral library: https://speclib.jpl.nasa.gov/documents/jhu_ desc; Salisbury et al., 1987;, and (C) rarer primary rock-forming silicates (Salisbury et al., 1987). ...
Lunar sulfides and oxides are a significant source of noble and base metals and will be vital for future human colonies’ self-sustainability. Sulfide detection (pyrite and troilite) applies to many technological fields and use cases, for example, as a raw material source (available in situ on the Lunar surface) for new solar panel production methods. Ilmenite is the primary iron and titanium ore on the Moon and can provide helium-3 for nuclear fusion and oxygen for rocket fuel. The most important ore minerals have prominent absorption peaks in a narrow far-infrared (FIR) wavelength range of 20–40 μm, much stronger than the spectral features of other common minerals, including significant silicates, sulfates, and carbonates. Our simulations based on the linear mixing of pyrite with the silicates mentioned above indicated that areas containing at least 10%–20% pyrite could be detected from the orbit in the FIR range. MIRORES, Multiplanetary far-IR ORE Spectrometer, proposed here, would operate with a resolution down to <5 m, enabling the detection of areas covered by 2–3 m² of pyrite (or ilmenite) on a surface of ∼17 m² from an altitude of 50 km, creating possibilities for detecting large and local smaller orebodies along with their stockworks. The use of the Cassegrain optical system achieves this capability. MIRORES will measure radiation in eight narrow bands (0.3 µm in width) that can include up to five bands centered on the ore mineral absorption bands, for example, 24.3, 24.9, 27.6, 34.2, and 38.8 µm for pyrite, marcasite, chalcopyrite, ilmenite, and troilite, respectively. The instrument size is 32 x 32 x 42 cm, and the mass is <10 kg, which fits the standard microsatellite requirements.
... The greens that make up the stems and leaves of the plants, in various shades, were constructed from a mixture of yellow and blue paints-chrome yellow or strontium yellow with cobalt blue or Prussian blue, further modifying the color with a small amount of Naples yellow (Pb2Sb2O7) or yellow ochre. The FTIR spectra showed bands at 475 and 652 cm −1 , attributed to Pb-O stretching and bending vibrations in Naples yellow [37,38]. The bands observed at 459, 660, 790, and 895 cm −1 , with a strong band at 1030 cm −1 , were assigned to goethite and silicate in yellow ochre. ...
The scientific examination and comparative investigation of pigments are fundamental for further understanding and analysis of historic and artistic works, and particularly useful for conservators. In fine art authentication, investigations are strongly focused on the identification of the painting materials used by the author. This study is focused on the use of non-invasive analytical techniques to increase the knowledge of the painting technique of Olga Boznańska. The aim of this study was to assess the technology, painting technique, and materials used by Olga Boznańska. The pallets, tubes with the paints, and several oil paintings were studied. For each painting, a series of images were recorded using various ranges of electromagnetic radiation, including near-infrared, visible light, ultraviolet, and X-rays. In order to characterize the pigments present in the paint layer, measurements of the elemental composition by X-ray fluorescence spectroscopy (XRF) were carried out. The ground layers and paints were measured with infrared spectroscopy (FTIR). This allowed us to identify the artist’s painting technique and determine how she executed her painting, how she applied the paints, and what pigments she used.
... Indeed, hematite presents these characteristic peaks and seems to be the main element characterising the red inscription analyzed [6]. Among the various results obtained from the different analyses of the red inscription, a very repeatable spectrum is the one shown in Fig. 3, which seems to describe characteristic peaks of an iron oxide earth pigment, the burnt sienna, which typically has a reddish-brown color and it is identifiable together with the peaks at 291.5 cm -1 , 410 cm -1 , 666 cm -1 and the one at 1323 cm -1 , overlapping the same Raman band as hematite [7]. Their detection is probably related to the presence of iron in the find or in the excavated ground. ...
... Compared to FTIR and Raman spectroscopy, a relatively high amount of powder is required for XRD. Some inorganic compounds (oxides, sulfides, etc.) have no vibrational modes in the mid-infrared region (the most common region to study cultural heritage materials), and their identification is only possible if the FTIR spectrometer is equipped with a far-infrared detector (650 to 50 cm −1 ) [18,19]. This step helps in the set-up and selection of the most appropriate desalination treatments to remove harmful salts from the artefacts and monitor the effectiveness of the cleaning procedures by studying the composition of the surface patina developed after the conservation treatment. ...
The multi-analytical protocol currently in use at Historic England for the investigation of copper alloy artefacts recovered during underwater excavations aims to determine their manufacturing processes, identify repairs, and assess their state of preservation. Each step of the scientific analysis is described, and the results obtained from the study of a selection of copper alloy objects recovered from the Dutch East India Company (VOC) Rooswijk shipwreck (1740) are used as examples of the application of the protocol to gain archaeological, metallurgical, and conservation data. This information is crucial to plan the most appropriate procedures and determine treatment steps for the study and conservation of copper alloy artefacts from the marine environment.
... Raman and Fourier transform infrared (FT-IR) spectroscopies are commonly used to determine pictorial compounds on cultural items, as specific chemical signatures of molecular vibrations can be unambiguously linked to given material compositions. 1,2 The two spectroscopies are often employed in a joint approach as molecules can be infrared (IR) and/or Raman active depending on their structural symmetry. Broadly speaking, Raman spectroscopy is utilized to detect symmetric vibrations and polar groups by measuring the scattered photons from a laser-excited sample. ...
... The peaks at 363 cm À1 and at 201 cm À1 generated by Cu-O and Ca-O vibrations were not detected. 1,39,40 Pb-Based Pigments Lead oxides have several polymorphic forms. The pigment named massicot (β-PbO) is the orthorhombic lattice structure of the lead(II) oxide and it assumed a yellow color. ...
This work demonstrates terahertz time-domain spectroscopy (THz-TDS) in reflection configuration on a class of inorganic and
mineral pigments. The technique is validated for pictorial materials against the limitations imposed by the back-reflection of the
THz signal, such as weak signal intensity, multiple signal losses and distortion, as well as the current scarce databases. This work
provides a detailed description of the experimental procedure and method used for the determination of material absorption
coefficient of a group of 10 pigments known to be used in ancient frescoes, that are, Cu-based (azurite, malachite, and Egyptian
blue), Pb-based (minium and massicot), Fe-based (iron oxide yellow, dark ochre, hematite, and Pompeii red) pigments and
mercury sulfide (cinnabar), and classified the vibrational modes of the molecular oxides and sulfides for material identification.
The results of this work showed that the mild signal in reflection configuration does not limit the application of THz-TDS on
inorganic and mineral pigments as long as (i) the THz signal is normalized with a highly reflective reference sample, (ii) the
secondary reflected signals from inner interfaces are removed with a filtering procedure, and (iii) the limitations at high
frequencies imposed by the dynamic range of the instrument are considered. Under these assumptions, we were able to
differentiate molecular phases of the same metal and identify azurite, Egyptian blue, minium, and cinnabar, isolating the
molecular vibrations up to 125 cm-1. The established approach demonstrated to be reliable, and it can be extended for the
study of other materials, well beyond the reach of the heritage domain.
... Materials that have no vibrational modes in the mid-infrared region, such as certain sulphides and oxides, can be analysed using a far-infrared (FIR) detector as these materials may absorb in the far-IR region (400-50 cm −1 ). 7,19 One of the first papers using IR spectroscopy to investigate ancient artefacts was published in 1966. 17 Here, an improvement of spectral resolution and detection limit was noted due to the development of FTIR spectroscopy in place of dispersive IR; the former technique has contributed enormously to archaeometry and conservation of cultural heritage since 1980s. ...
Scientific investigation of cultural heritage objects plays a vital role in a responsible modern approach to conservation and archaeology. Recent advances in spectroscopy, such as the development of Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy and ATR-FTIR spectroscopic imaging, have opened up a window of opportunities for characterisation of materials in artefacts and collections from museums. This review summarises some of the recent advances and applications of these ATR-FTIR spectroscopic analytical techniques in the area of cultural heritage studies, including examples of cross-sections of oil paintings, paper, textiles, plastic objects, potteries, glasses and mineral artefacts. Two of the major advantages of ATR mode measurements are minimal or no requirements for sample preparation and its provision for high lateral spatial resolution. In addition to conventional single point detection, two-dimensional mapping and imaging is especially beneficial for chemical visualisation of multi-layered structure cultural objects. This review also explores the implications of these advantages as well as some limitations and provides a brief outlook for the possible future developments in this area.
... Regarding the pigments, the Raman spectrum of the red pigment clearly shows the characteristic peaks of iron oxide at 225 cm −1 , 293 cm −1 , 410 cm −1 , 497 cm −1 , 611 cm −1 , 1317 cm −1 , assigned to ν s (Fe-O), δ s (Fe-O), and ν as (Fe-OH) [42,43]. An additional peak at 659 cm −1 may belong to iron impurity in the form of magnetite, or to a disorder band in the crystalline structure of hematite, caused by exposure to a high temperature during burning [44,45]. On the other hand, the lampblack pigment is characterized by the two broad bands of amorphous carbon-at 1315 cm −1 and 1591 cm −1 -assigned to the D-and G-bands of CC, respectively [46,47]. ...
Fluorescence analysis of materials used as binders and coatings in artworks is often hampered by numerous factors, leading to uncertainties in data interpretation. Fluorescence lifetime (FL) measurements enable improvement of the specificity with respect to steady-state measurements by resolving the decay dynamics of the fluorophore emissions. In this work, layers of natural resin, oil, and wax—in pure form, pigmented, in mixtures, and spread on different substrates—were analyzed using a compact, portable, fiber-based FL instrument. FL data were processed via the phasor method and integrated with Raman spectroscopy to obtain complementary chemical information on the different substances. It was observed that the τ-phase of the mixtures is affected by both the pigments and the dispersing medium, and that the presence of the metal substrate contributes to changes in the FL of mixtures. The results obtained with our portable FL system combined with Raman spectroscopy pave the way for a systematic study of a larger number of materials for future in situ applications on works of art.
... 13 The spectral region accessed by far-FTIR has been exploited for overcoming the limitations of mid-FTIR and Raman spectroscopy in pigment identification, especially for inorganic compounds derived from minerals. 14,15 Far-IR radiation excites lattice vibrations that are unique to specific solid-state structures with significantly different frequencies found for crystalline polymorphs of the same chemical compound. ...
Terahertz spectroscopy, a non-invasive and non-destructive analytical technique used in art conservation and restoration, can provide compelling data concerning the composition and condition of culturally valuable and historical objects. Terahertz spectral databases of modern and ancient artists’ pigments exist, but lack explanations for the origins of the unique spectral features. Solid-state density functional theory simulations can provide insight into the molecular and intermolecular forces that dominate the observed absorption features, as well as reveal deviations from simple harmonic vibrational behavior that can complicate these spectra. The characteristic terahertz spectra of solid azurite, malachite, and verdigris are presented here, along with simulations of their crystalline structures and sub-3.0 THz lattice vibrations. The powerful combination of theory and experiment enables unambiguous spectral assignment of these complex materials and highlights the challenges that anharmonic peak broadening in organic-containing materials may present in the construction of reference pigment databases.
... (1) There are a number of interesting inorganic compounds (pigments, some fillers, and minerals) that have characteristic absorption bands in the region of 500-80 cm -1 and are often present in samples or on their surfaces at concentrations high enough for ATR-FT-IR analysis [8,9,12,13]. In general, vibrations involving heavy atoms as well as lattice vibrations in crystals are found in that region. ...
In this paper, a spectral collection of over 150 ATR-FT-IR spectra of materials related to cultural heritage and conservation science has been presented that have been measured in the extended region of 4000-80 cm–1 (mid-IR and far-IR region). The applicability of the spectra and, in particular, the extended spectral range, for investigation of art-related materials is demonstrated on a case study. This collection of ATRFT-IR reference spectra is freely available online (http:// tera. chem. ut. ee/ IR_ spectra/ ) and is meant to be a useful tool for researchers in the field of conservation and materials science.
... Although the majority of infrared studies is performed in the mid-IR range (4000-400 cm À 1 ) where so-called fingerprint region for organic compounds is located, in the case of inorganic compounds a number of informative vibrational bands are shifted to the far-IR region (roughly defined as below 400 cm À 1 ). Far-IR spectroscopy has proven itself to be a valuable technique, e.g. to study the spin crossover compounds [1], phonons and plasmons in semiconductor superlattices [2], intermolecular interactions between cations and anions in ionic liquids [3] and even for analyzing inorganic pigments and corrosion products found on art objects [4,5]. ...
... Insufficient transparency of the pellets made of PE powder is a well-known problem in the field of far-IR spectroscopy, and several methods have been suggested to solve it, at least to some extent. Heating of the pellet die during pellet formation up to the melting point of the PE ( $ 130-180 C) allows one to homogenize the pellet [4,6], approaching the transmission properties of the PE matrix to bulk PE material. But this approach can be applied only for thermally stable samples. ...
Similar to potassium bromide (KBr), which is used in mid-IR as a matrix for pellet preparation, polyethylene (PE) is widely applied in far-IR because it is an inert material without intensive absorption lines in this range. However, despite the material itself being transparent, the transmission of pellet made of PE powder strongly depends on the wavelength tending to decrease almost to zero in a short-wave part of the far-IR range. Heating of the pellet to PE melting temperature significantly improves its transparency, but this approach can only be applied to thermally stable compounds. In this work 8 types of PE powders of different mean particle size (MPS) ranging from 43 to 3 µm have been synthesized. Far-IR spectra of PE pellets made of these powders at room temperature have been measured and the inverse correlation between overall far-IR pellet transparency and MPS of its PE powder has been found. The imaginary part of the effective refractive index of the studied pellets obeys light-scattering scale invariance rule, indicating that the transmission of PE pellets is limited by light scattering by PE grains. It has been shown that PE powders with MPS of ~4 µm or less are suitable as a matrix for pellet preparation in far-IR spectroscopy without the necessity of pellet melting.
