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Heritage Science 7(1), 67 (2019). doi:10.1186/s40494-019-0309-3, The use of non-invasive macroscopic imaging techniques is becoming more prevalent in the field of cultural heritage, especially to avoid invasive procedures that damage valuable artworks. For this purpose, an X-ray powder diffraction scanner (MA-XRPD) capable of visualising crystalline compounds in a highly specific manner was recently developed. Many inorganic pigments present in paintings fall into this category of materials. In this study, the 17th century oil painting Girl with a Pearl Earring (c. 1665) by Johannes Vermeer was analysed with a combination of transmission and reflection mode MA-XRPD. By employing this scanner in reflection mode, the relative sensitivity for compounds that are present at the paint surface could be increased, establishing it as a highly relevant technique for investigating the degradation processes that are ongoing at paint surfaces. Many of the original pigments employed by Vermeer could be identified, along with four secondary alteration products: gypsum (CaSO4·2H2O), anglesite (PbSO4), palmierite (K2Pb(SO4)2) and weddellite (CaC2O4·2H2O). The formation of gypsum was linked to the presence of chalk in the upper glaze layer while the formation of palmierite and weddellite is driven by the presence of lake pigments (and their substrates). In this manner, MA-XRPD can also be used to pinpoint locations relevant for sampling and synchrotron µ-XRPD analysis, which provides information on the microscopic make-up of the paint. A paint cross-section taken from an area rich in palmierite was analysed with synchrotron µ-XRPD, which confirmed the presence of this secondary compound at the interface of the upper paint layer with the ground layer as well as the presence of anglesite in the ground layer. The capacity of MA-XRPD to identify and chart secondary alteration products in a non-invasive manner has only very recently been demonstrated and makes it a highly relevant technique for the assessment of the chemical condition of works of art., Published by Chemistry Central, London

Minerals, as raw structural materials or pigments, play a fundamental role in archaeometry, for the understanding of nature, structure and status of an artefact or object of interest for cultural heritage. A detailed knowledge of the mineral phases is crucial to solve archaeological problems: Raman spectroscopy is a powerful investigation technique and has been applied extensively in the last 30 years on mineral identification and on pigment degradation. Here we report an updated review, covering the last decade, of the applications of Raman techniques to issues in which raw minerals, including mineral pigments, are involved. Particular attention is devoted to cases where the Raman analysis of minerals is deeper than a simple identification of the phases present in an archaeological or artistic object. Copyright © 2016 John Wiley & Sons, Ltd.

Sea-ice samples intended for biological analyses, e.g., chlorophyll-a, cell enumeration of algae and protozoa and primary production, are affected by the sampling and sample processing methods. In this study, we compared different sample processing methods by melting Baltic Sea ice samples in different ways (direct melting, buffered melting in filtered seawater (FSW) and buffered melting in artificial seawater at two different salinities with added nutrients) at two temperatures [+4 °C and room temperature (RT)]. We show that sea-ice samples intended for most commonly used biological analyses can be melted without the addition of FSW. In particular, adding artificial seawater should be avoided. To minimize biological processes, such as growth, death, predation and pigment degradation, the melting should be done rapidly at RT preferably by gently shaking the sample to keep the melt cool.

Mural paintings of exceptional quality, which can be discerned in spite of their extensive mechanical damage and colour fading, have been uncovered in the church of St. Gallus in Kuivody, Northern Bohemia, dated to the second half of the 13th century. Materials research with particular use of portable X-ray fluorescence, Raman micro-spectroscopy and powder X-ray micro-diffraction revealed the presence of rare pigments. In Kuivody, it is only a second identification of intentionally used yellow mineral crocoite (PbCrO4) in European art. Its identification is facilitated by providing a very good Raman scattering, even when present in small amounts in fragmentarily preserved colour layers. Light yellow mimetite (Pb-5(AsO4)(3)Cl) was never before mentioned as intentionally used pigment in Europe. Its finding in Kuivody, however, corresponds more likely with undesirable physical-chemical conditions causing its formation by alteration of orpiment (As2S3) and minium (Pb3O4). Obtained results highlight the importance of Raman spectroscopy for direct identification of mineral pigments in low concentrations, which may be crucial for interpreting cultural heritage objects in historical context. By materials, the almost forgotten paintings in Kuivody can be seen as outstanding and rare example of ancient artistic tradition that has spread to Europe from Mediterranean in early Middle Ages. After all, mineral crocoite was already used by ancient Egyptians to paint sarcophagi and degraded orpiment decorates the walls of the Nefertari's tomb in Thebes.

Portable X-ray Fluorescence Spectrometry (pXRF) was used to survey 33 works in Washington and Lee University’s collection of Louise Herreshoff’s paintings. This work was done both to support a condition assessment of the paintings and their pigments and to determine which paintings might be appropriate for further study in the context of ongoing key synchrotron research into the degradation mechanisms of cadmium sulfide yellow pigment (CdS).

For the first time the degradation of lead white pigment in mature oil paint has been used as an internal marker for the degree of saponification and hence chemical degradation of oil paint. Computational image analysis of the backscattered electron images quantified the degree of the intact lead white pigment versus the nonpigmented and lead-rich areas (degraded lead white) in the paint layers. This new methodology was applied to a series of paint samples taken from four painted wall hangings (dated 1778), which makes it possible to study the influence of indoor climate on chemical degradation of aged oil paintings. The visual interpretation and computational image analysis of the backscattered electron images revealed clear trends. The highest degree of lead white degradation in the room was found in samples from the north wall close to the windows, whereas degradation diminished further away from the window. Lead white from the south wall was less degraded, but showed a similar trend as in the paintings on the north wall. These results imply a strong relationship between chemical degradation of paint and location of the paint in the room.

Raman microscopy has been used to identify the pigments decorating three valuable items owned by the Worshipful Company of Barbers (established in 1308 in London), one being a large leather screen dating to before 1712, the other two being illuminated title pages of books of ordinances of the Company dating to 1605 and 1658. Pigments which could not be fully characterised by this technique (particularly the green paints) have also been subject to XRF or SEM–EDX analysis. The combined analytical approach has shown that the pigments identified on all three items are typical of those in use as artists’ pigments in the 17th C and include azurite, indigo, vermilion, red lead, pink and yellow lakes, verdigris, lead white, calcite (and chalk), gypsum, carbon-based black, and gold and silver leaf. However in the case of the screen alone, restoration in the 1980s has been carried out with different pigments – haematite, phthalocyanine green, rutile, and a mixture of azurite, malachite and barium sulfate. This work constitutes the first in-depth study of painted leatherwork and demonstrates that the palette used for this purpose is similar to that used on other works of art of the same date. It has also allowed the original colour schemes of the decorations to be determined where pigment degradation has occurred. The combined analysis has also provided a more complete understanding of the materials used for, or on, objects to which access is limited.

Sliced cooked ham was vacuum packaged and held in the dark at −15C. 10C, and 30C, and at 10C in the light, for up to 96 h. At 24 h intervals, samples were analyzed for pigment concentration by spectrophotometry. A decrease in pigment concentration was observed over time under all conditions. Pigment degradation increased at higher temperatures and with light exposure. Kinetic parameters were determined, indicating that pigment degradation follows first order kinetics and the temperature dependence of these reactions indicated an Arrhenius relationship. The activation energy was 3.3 kcal/mol. The visible spectra for the extracted pigments in cooked ham showed the typical pattern of nitrosylmyoglobin. Pigments extracted from ham displayed in the light had spectra with similar absorption maxima to those from those stored in the dark.

Publisher Summary This chapter discusses the molecular structures, the general physicochemical properties of plant pigments, and the mechanisms involved in pigment degradation. The invasive and noninvasive methods used for pigment analysis, including the mechanisms involved in pigment degradation, are reviewed. The chapter presents different analytical methods that can be used to identify pigments. All the methods are invasive techniques that are time consuming and often expensive. To reduce sampling and analytical costs, and to speed up the analyses, noninvasive analytical procedures have been developed with the aim to characterize the pigment content of samples, and in the case of food products, to estimate the impact of a color change on the visual perception of the product. The complete extraction of pigments requires several steps and may use a mixture of several solvents. This is true when the sample contains pigments of different polarities or pigments that are present in a complex matrix. Research on plant pigments is fascinating because it involves many methods and a deep knowledge in several fields. Plant pigment studies should be continued because they may procure several immediate interesting impressions, and commercial and health advantages.

Carbon dioxide flushing and packaging under slight overpressure has been found to eliminate discoloration of vacuum-packed ham, normally encountered as a result of photooxidation of nitric oxide pigments during the first 24 h of display in illuminated cabinets. On exposure to light, even when the product is packed in high-vacuum, residual oxygen invariably present in the product gives rise to significant photochemical pigment degradation and general poor oxidative stability, and has warranted up to 4 days of dark storage prior to display. Replacement of the atmosphere with carbon dioxide, even when repeated, followed by the establishment of vacuum, does not yield a similar protection.