Red Lead Pigment Research Articles

Insight into thermally-induced reduction of Plattnerite into red lead pigment

Insight into thermally-induced reduction of Plattnerite into red lead pigment

A combined theoretical and experimental investigation of the electronic and vibrational properties of red lead pigment

The electronic and vibrational properties of red lead pigment, the mixed valence lead oxide compound Pb3O4, known as minium, have been studied by means of first principle calculations based on Density Functional Theory (DFT) and Fourier Transform–Infra Red (FT-IR) and Raman spectroscopies. The aim of the present investigation is to validate an integrated theoretical-experimental approach for modelling the structural, electronic and spectroscopic properties of minium and to define its structure-properties relationships. The calculated band gap performed using GW approximation is in excellent agreement with the experimental one and improves previous results found in literature. The simulated vibrational IR and Raman spectra are able to reproduce the main features of the experimental spectra and to assign the normal modes related to the experimental bands. The combined theoretical and experimental study of the electronic and vibrational properties of Pb3O4 allows to clarify the mechanism of lead whitening as well as to interpret ambiguous Raman spectra of minium in terms of resonance effects.

Investigation of the Optical, Physical, and Chemical Interactions between Diammonium Hydrogen Phosphate (DAP) and Pigments

This research investigates and evaluates the optical, physical, and chemical interactions between diammonium hydrogen phosphate (DAP) and seven pigments commonly encountered in archaeological and historic fresco and secco wall paintings and polychrome monuments. The pigments include cinnabar, French ochre, chalk, lapis lazuli, raw sienna, burnt umber, and red lead. The raw pigments were analyzed before and after the interaction with DAP, and the reaction products resulting from the contact of the pigments with the DAP solution were evaluated to obtain a comprehensive understanding of the effects of diammonium hydrogen phosphate on the color, morphology, and chemical composition of the pigments. The results indicated no significant change of the color or of the chemistry of cinnabar, French ochre, and lapis lazuli. Carbonate-containing pigments, such as chalk and calcium carbonate, were transformed into calcium phosphate, though without a significant change in color. Phase and strong color changes occurred only for the red lead pigment, associated with the transformation of red lead into hydroxypyromorphite. These data established the parameters and identified the risks of the direct application of DAP solutions on pigments. Further research will be undertaken to assess the potential use of DAP as a consolidant of wall paintings and other polychrome surfaces through testing on wall painting/polychromy mockups and on-site archaeological/historic painted surfaces.

Degradation of red lead pigment in the oil painting during UV aging

AbstractThe degradation product and mechanism of red lead pigment (Pb3O4, minium) in pure powder and in modeled oil painting are dynamically tracked during ultraviolet light aging by the change of color, crystal structure, chemical composition, and surface morphology. After UV aging, the color of pure minium pigment gradually darkens from bright orange‐red into black, but the color of model paint samples made by minium and tung oil binder changes into brownish and whitish color (ΔE* = 56.60). After aging, the crystal structure of Pb3O4 powder is proved to transfer into plattnerite (β‐PbO2) by X‐ray diffraction (XRD) pattern, but the degradation product of Pb3O4 in model paint samples is identified as 2PbCO3·Pb(OH)2 by the noticeable peaks at 24.8°, 27.4°, and 34.3° in XRD pattern, and two new Fourier transform infrared peaks at 1393 cm−1 and 682 cm−1 attributed to the presence of , and a new peak at 1051 cm−1 in Raman spectroscopy. During UV aging, the model paint samples' surface is verified gradually from wrinkled surface into nanoscale sheet‐like structure and finally a regular hexagonal plate‐like crystal structure, showing hexagonal crystals of hydrocerussit 2PbCO3·Pb(OH)2. This reveals the interaction between organic tung oil binder and inorganic minium to accelerate the degradation of Pb3O4 pigment. Therefore, the degradation mechanism is deduced as that CO2 and H+ formed by oxidizing ester/carboxyl groups in tung oil reacts with Pb2+ to yield the white product of 2PbCO3·Pb(OH)2. It is believed that this study will contribute much to the complete understanding of the degradation of minium pigment in oil paintings.

A new approach to the determination of the synthetic or natural origin of red pigments through spectroscopic analysis

This work suggests a way of differentiation between the natural or synthetic origin of inorganic materials that were historically used in the Cultural Heritage field. An exhaustive review of different reported procedures of synthesis of pigments was conducted, as well as a review of the accompanying minerals in case of natural pigments. The natural or synthetic origin of the pigments studied in this work was performed through the characterization of the accompanying minerals, in the case of the natural pigments, or the trace elements that are present as part of synthesis by-products or washing/purifying reagents and/or reactants that have only been partly removed in the final steps of these processes. This work characterized red pigments due to their wide variety, complexity and possibility of use in different mixtures. The following pigments were studied: cinnabar-vermilion, red lead and iron pigments. Also mixtures of these pigments between them and with red lake were also studied. Natural cinnabar was accompanied by silicon oxide (opal, chalcedony or quartz), calcite, clay minerals and, sometimes, pyrite. K together with S indicated a synthetic pigment (vermilion) obtained through the wet method. Nevertheless, K has not been found in layers containing only vermilion in our samples. The presence of Sn in some cases indicated vermilion that came from the dry process. K from the synthesis always appeared in the red lead pigment. The red natural ochre was confirmed by presence of clay minerals and iron. It should be said that Ca and S, and sometimes Al and K, were usually found in Mars red pigment. The presence of Al and Ca allowed the identification of carmine lake.

Construction of Spectral Discoloration Model for Red Lead Pigment by Aging Test and Simulating Degradation Experiment

The construction of spectral discoloration model, based on aging test and simulating degradation experiment, was proposed to detect the aging degree of red lead pigment in ancient murals and to reproduce the spectral data supporting digital restoration of the ancient murals. The degradation process of red lead pigment under the aging test conditions was revealed by X-ray diffraction, scanning electron microscopy, and spectrophotometer. The simulating degradation experiment was carried out by proportionally mixing red lead and lead dioxide with referring to the results of aging test. The experimental result indicated that the pure red lead was gradually turned into black lead dioxide, and the amount of tiny particles of the aging sample increased faced with aging process. Both the chroma and lightness of red lead pigment decreased with discoloration, and its hue essentially remains unchanged. In addition, the spectral reflectance curves of the aging samples almost started rising at about 550 nm with the inflection moving slightly from about 570 nm to 550 nm. The spectral reflectance of samples in long- and in short-wavelength regions was fitted well with the logarithmic and linear function. The spectral discoloration model was established, and the real aging red lead pigment in Dunhuang murals was measured and verified the effectiveness of the model.

Synchrotron-based scanning macro-X-ray fluorescence applied to fragments of Roman mural paintings

Roman wall fragments dating from 2nd and 3rd centuries AD, from two sites of the Roman province of Germania Superior, near the present day towns of Wössingen (Baden-Württemberg) and Mülheim-Kärlich (Rheinland-Pfalz), were analyzed with synchrotron-based scanning macro-X-ray fluorescence (SR-MA-XRF) at the FLUO beamline (ANKA Synchrotron Radiation Facility, Karlsruhe Institute of Technology). Lead, iron, copper, calcium, potassium, among other elements, were detected and are correlated with red, blue, yellow and green pigments. In the fragments from Mülheim-Kärlich, red has high correlation with Pb (red lead pigment), Fe and Ca were detected in 2 different hues of yellow respectively, and Cu is correlated with the blue pigment. The green pigment investigated in the Wössingen's fragments has high correlation with Fe and K, indicating the use of green earth, and the red pigment is correlated with iron, indicating the use of the red ochre. Synchrotron-based scanning macro-X-ray fluorescence applied in fragments of wall paintings has shown to be a fast, non-destructive and effective technique in the identification and discrimination of the pigments, plaster, different layers and impurities in paintings through the 2D elemental distribution.

Spectroscopic analysis of pigments and inks in manuscripts. III. Old-Slavonic manuscripts with multicolored rubication

Raman spectroscopy, FTIR spectroscopy and SEM-EDS were applied in characterization of pigments and inks in five old-Slavonic manuscripts: Kičevo Four Gospel (16th century), Zrze Four Gospel (16th/beginning of 17th century), Struga Four Gospel (beginning of 17th century), Kruševo Ochtoechos (second half of 15th century) and Psalter with rituals (beginning of the 16th century). The illuminations used in the first four manuscripts are in so called Balkan style characterized with interlaced rings and floral motifs, with rarely seen, multicolored rubication text: in Kičevo and Zrze Four Gospel manuscripts are written in four colored inks: black-brown, blue, red and purple-red while in Struga and Kruševo Ochtoechos manuscripts is black-brown, blue and red inks. Psalter with rituals is a manuscript from the same period, with typical rubication in red and was included in the study as standard form of manuscript. In addition to several types of gall ink identified as brown-black ink used in the manuscripts, carbon black ink and logwood ink were also identified. In colored inks, azurite or mixture of azurite and indigo were used as blue ink while vermilion or mixture of vermilion and red lead was used as red ink. Another, purple-red ink of organic nature was used as well. The pigments identified in ornaments are: azurite and indigo in blue colors, orpiment as yellow pigment, vermilion, red lead and organic red pigment as reds, while green pigment was identified as organo-Cu complex. Brown-black ink was used for framing the illuminations and illuminated initial letters and pure gold for gilding. In spite of similar style and pigments, slight but characteristic differences in pigments and inks used, suggest different scriptoria.

Red lead darkening in wall paintings: natural ageing of experimental wall paintings versus artificial ageing tests

The mechanisms of red lead pigment darkening were investigated through complementary observations and analyses of naturally aged experimental wall paintings. Red lead transformation into mainly plattnerite [β-PbO 2 ] and also anglesite [PbSO 4 ] was established by mineralogical analyses of a micro-sample using focused X-ray diffraction and confirmed by micro-Raman spectroscopy. According to both optical and electron microscopy observations, β-PbO 2 appears to have formed in the outer part of the paint surface, while PbSO 4 is only located in a thin superficial layer. Structural features of plattnerite crystals were investigated using both scanning and transmission electron microscopy. Besides, red lead stability in various conditions was assessed by means of a set of physico-chemical tests applied on both raw pigment and experimental paintings. The pigment alteration is assumed to occur through the sulfation into anglesite of lead monoxide initially present in the pigment, followed by the so-called “solvolytic disproportionation” of Pb 3 O 4 . Such an alteration process is controlled by environmental parameters, namely humidity, temperature and sulfate concentration, which depend on the oxidative dissolution of atmospheric SO 2 pollutant.

江戸時代木版本・鼓銅圖録(こどうずろく)に使われた鉛丹の微細構造と変色

The microstructures of red lead (minium) pigment and the behavior of the Pb species used in the wood-block-printed book Kodouzuroku published in the late Edo period have been investigated. A copper refining technique of the late Edo period is described in this book. Although the red lead pigment was used for the color of the flames in the illustration of the refining process, the color has long changed from red to black. A very small specimen is taken from the picture and then thinned by the focused-ion-beam method. The microstructures are observed using a transmission electron microscope. The Pb3O4 crystals exhibiting the red-color are detected in the pigment layer. The crystal diameter is 6~17 nm. Pb species that diffused from the pigment layer into the glue, which was used as a binding medium, are detected. The diffused Pb species are also detected in the paper fiber. Furthermore, nanosize αPbO particles have precipitated in the paper fiber. The Pb species diffused into the glue and paper fiber cause the blackening of the pigment layer and the paper fiber.

The fading of red lead pigment in wall paintings: tracking the physico-chemical transformations by means of complementary micro-analysis techniques

The phenomenon of red lead pigment fading in wall paintings was investigated through the study of an experimental fresco painting. Chemical modifications of the pigment induced a local fading of the pictorial layer after a 25-years natural ageing period. Representative features of the alteration phases, including composition and structural information, were obtained by applying complementary micro-analysis techniques to the study of a single paint sample. Focused X-ray diffraction patterns of small areas were collected using a highly sensitive detector, revealing the transformation of red lead pigment into both cerussite (lead carbonate) and anglesite (lead sulphate). The distribution of Pb, S, O and Ca elements within the cross-section was established using electron micro-probe analysis, and correlated to micro-Raman semi-quantitative mappings of minium (Pb3O4), cerussite (PbCO3), anglesite (PbSO4) and calcite (CaCO3) phases. The micro-structural characteristics of each lead-containing phase were investigated by means of scanning electron microscopy observations of the sample cross-section using backscattered electron imaging. The major role of atmospheric pollutants (SO2, CO2), together with water condensation on such a red pigment fading is emphasised.

Study of the pigment type effect on the corrosion behaviour of epoxy painted steel/ sea water systems

The effect of different kind of pigments on the corrosion resistance properties of an epoxy paint has been investigated using electrochemical impedance spectroscopy and open circuit potential measurements. Painted naval steel samples were studied during the exposure to artificial sea water. The epoxy paint coatings were prepared employing red lead, zinc, red iron oxide or titanium dioxide as pigment with 0.8 of PVC/CPVC ratio. From the EIS and corrosion potential data analyis was found that the anticorrosive protection given by an anticorrosive (pigmented with red lead) and a top coat (pigmented with red iron oxide) epoxy painting scheme was both more lasting and more effective. This was attributed to the fact that both the effective adhesion provided by the chemical bonding between the steel surface and the epoxy paint groups and the constant high barrier effect afforded by this type of top coat were a perfect complement for the high corrosion inhibitive capacity of the red lead pigment.

Study of the pigment type effect on the corrosion behaviour of epoxy painted steel/sea water systems

The effect of different kind of pigments on the corrosion resistance properties of an epoxy paint has been investigated using electrochemical impedance spectroscopy and open circuit potential measurements. Painted naval steel samples were studied during the exposure to artificial sea water. The epoxy paint coatings were prepared employing red lead, zinc, red iron oxide or titanium dioxide as pigment with 0.8 of PVC/CPVC ratio. From the EIS and corrosion potential data analyis was found that the anticorrosive protection given by an anticorrosive (pigmented with red lead) and a top coat (pigmented with red iron oxide) epoxy painting scheme was both more lasting and more effective. This was attributed to the fact that both the effective adhesion provided by the chemical bonding between the steel surface and the epoxy paint groups and the constant high barrier effect afforded by this type of top coat were a perfect complement for the high corrosion inhibitive capacity of the red lead pigment.

Further evidence of lead contamination of Omaha skeletons.

A previous analysis of Omaha skeletons dating between A.D. 1780 and 1820 revealed the presence of lead in all skeletons with high concentrations in children and adult males (Reinhard and Ghazi [1992] Am. J. Phys. Anthropol. 89:183-195). Two likely explanations for the high lead levels were presented: 1) metabolic absorption of lead and 2) diagenetic uptake of lead by the bones from postmortem application of pigments to the corpse. Two types of lead were available to the Omaha tribe: 1) Mississippi Valley type, and 2) non-Mississippi Valley type. It has been suggested that red-lead pigment mixed with mercury sulphide (cinnabar) applied to the corpse may have been one of the sources of lead found in bones. Further isotopic analyses of samples of pigment and metallic lead artifacts associated with the skeletons revealed that non-Mississippi Valley type lead is present in the pigment while Mississippi Valley type lead comes from metallic artifacts. Both lead and mercury were found in the pigment samples, verifying that a lead-based pigment mixed with cinnabar-based pigment was used as a cosmetic by the Omaha. Isotopic analysis of lead in skeletons indicates that the pigment contributed most to lead content of bone. This new evidence clarifies the previous study and suggests specific mechanisms by which lead became incorporated into bone.