Search results for "PIGMENT"
showing 10 items of 626 documents
CORRELATION BETWEEN SPECTRAL, SEM/EDX AND ELECTROCHEMICAL PROPERTIES OF MAYA BLUE: A CHEMOMETRIC STUDY*
2009
Visible spectra, composition from SEM/EDX and solid-state electrochemical data are correlated for a set of 12 Maya Blue samples from different archaeological sites of Campeche and Yucatan (Mexico). In addition to indigo and dehydroindigo, indirubin and other possibly indigo-type compounds can be detected in Maya Blue samples. Application of hierarchical cluster analysis techniques allows similarity relationships to be established between samples from different sites, confirming prior results which suggest that the preparation of Maya Blue pigment evolved with time during the Maya culture following a ramified scheme.
IDENTIFICATION, PROCESSING AND USE OF RED PIGMENTS (HEMATITE AND CINNABAR) IN THE VALENCIAN EARLY NEOLITHIC (SPAIN)
2012
The results of the first elemental and structural physicochemical analyses (SEM–EDX, TXRF, XRD, FTIR, GC and EDXRF) of Early Neolithic red pigment samples from the region of Valencia confirm one of the earliest uses of cinnabar (HgS) in Spain (5300 to 5000 cal bc). They also inform on the storage of massive quantities of hematite and the development of specific technologies of hematite-based paint production and use. The samples were recovered at the three most significant Early Neolithic sites of the Mediterranean coast of Spain: Cova de l'Or (Beniarres, Alacant), Cova de la Sarsa (Bocairent, Valencia) and Cova Fosca (Vall d'Ebo, Valencia), which together have provided the most important E…
The blue enamels in the baroque decorations of the churches of Palermo, Sicily: Fe2+-coloured glasses from lime kilns
2009
Deep blue glasses coloured by octahedral Fe 2+ cations are often reported as textbook examples of blue pigmentation. However, despite the possibility of laboratory synthesis under reducing conditions, to date there are no well-reported occurrences of their production and use in the past. A thorough historical, ethnographic, mineralogical, and chemico-physical investigation of the 'smaltini di calcara' from several baroque churches in Palermo, Sicily, has revealed that the blue enamels widely used for altar decorations in the 17th and 18th centuries are actually a unique case of ancient blue glasses pigmented by divalent iron cations in distorted octahedral coordination. This mixed-alkali gl…
EDXRF analysis of blue pigments used in Valencian ceramics from the 14th century to modern times
2006
Abstract EDXRF analyses of cobalt-blue pigments were performed on 73 pieces of Valencian ceramics from the beginning of the 14th century up to the 20th century. In 67 of such samples, the pigment decoration was applied together with a tin opacified lead glaze cover on the clay body. In five samples the pigment was applied on the clay body without a glaze cover. The comparison between EDXRF spectra from coloured and non-coloured areas contains information about the pigment composition. Elements like Mn, Fe, Co, Ni, Cu, Zn and As are identified as characteristic of blue pigments; different associations of these elements were found and correlated with the chronology of the samples. The results…
Spectroscopic analysis used to uncover the original paint colour of the Helsinki Government Palace tower clock faces
2016
The paint stratigraphy of the two clock faces from the tower clock of the Government Palace in Helsinki (Finland) was analysed in order to determine their original colour before restoration works. Paint cross-section samples from both clock faces were analysed by confocal Raman microscopy and scanning electron microscopy coupled to an energy dispersive X-ray spectrometer (SEM-EDS). The results revealed the complex superimposition of paint layers applied over the original black colour. FTIR/ATR analyses proved that the original paint was prepared with linseed oil-resin media. Most likely not all of the different layer colours were visible. Some of the layers were likely to have been a primer…
Analyzing chemical changes in verdigris pictorial specimens upon bacteria and fungi biodeterioration using voltammetry of microparticles
2017
[EN] It is reported the application of the voltammetry of microparticles (VMP), complemented with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and field emission scanning electron microscopy (FESEM) techniques, to monitor the deterioration of verdigris pictorial specimens under the action of different biological agents. This methodology would be of application for identifying the type of biological agent causing deterioration of paintings, which is an important problem affecting cultural heritage. The analysis of biodeterioration processes is complicated by the fact that the action of microorganisms can affect both pigment and binding media. The deteriorat…
Characterization of Color Production in Xalla´s Palace Complex, Teotihuacan
2020
A multi-analytical approach was used to characterize color remains from Xalla, a Teotihuacan palace complex (project Teotihuacan, Elite and Government. Excavations in Xalla led by Linda R. Manzanilla). Color samples were obtained from polished lithic instruments and pigment ores. Those samples were analyzed combining microscopic and spectroscopic techniques. Our results coincide with previous studies in Teotihuacan, with the chromatic palette displaying a predominance of iron oxides such as hematite, yellow ochre and natural earths, as well as malachite, celadonite and glauconite. We have enlarged the corpus of raw materials with the characterization of jarosite and bone white and mica as a…
A smartphone-based innovative approach to discriminate red pigments in roman frescoes mock-ups
2022
The characterization of red pigments in frescoes wall paintings has been of great interest for researchers to better understand raw material procurement dynamics, pigment receipts, stylistic evolution and to assess their conservation state. In this study a non-destructive colorimetric approach implementing a smartphone-based method was developed in order to be able to distinguish between three pigments made from minium, haematite and cinnabar minerals, and also mixed pigments, preparing frescoes mock-ups following the roman receipt described by Vitruvius. Portable FT-IR, Raman spectroscopy, portable XRF and visible reflectance spectra analyses were carried out as reference methods for smart…
Photobleaching measurements of pigmented and vascular skin lesions: results of a clinical trial
2011
The autofluorescence photobleaching intensity dynamics of in vivo skin and skin pathologies under continuous 532 nm laser irradiation have been studied. Overall the 141 human skin malformations were investigated by laser induced skin autofluorescence photobleaching analysis. Details of equipment are described along with some measurement results illustrating potentiality of the technology.
Pigmented desmoplastic trichilemmoma
2016
Desmoplastic trichilemmoma (DT), the pseudomalignant variant of conventional trichilemmoma described by Hunt et al in 1990, displays a superficial lobular growth pattern of glycogen-rich cells with peripheral nuclear palisading surrounded by a thickened basement membrane. DT differs from its conventional counterpart by showing a central hyalinized area with epithelial cords and strands mimicking invasive carcinoma. We report a case that fully satisfies the criteria for DT and, in addition, shows an extensive melanocytic cell component and prominent melanin deposition. To our knowledge, a pigmented variant of DT has not been reported and should be recognized in order to appropriately face th…