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Pigmentveränderung
(2009)
The great variety of manuscripts found in the Turfan oasis at the Start of the twentieth Century by Grünwedel and Le Coq reflects the cultural backgrounds of, and communication among, the people who travelled along the network of Eurasian trade routes. Specifically, this Connection is directly reflected by the use and distribution of inks, pigments, and papers. Research is now underway to examine these and a report on the initial findings is given below.
The development of anti-corrosive pigments for the most diverse coating Systems is extremely time consuming and expensive, owing to the necessary climatic testing, such as testing under salt spray exposure. To accelerate work on a new zinc-free pigment with improved protection, modern, electrochemical investigation methods have been used successfully and verified using traditional tests.
Microcolonial fungi (MCF) are the most stress-resistant eukaryotes known to date. Black fungi are an interesting object to study mechanisms of stress resistance and to perform applied research to prevent material colonization and biodeterioration. Pigments, like melanin and carotenoids, have been proven to contribute to the unique robustness of MFCs. We study how these pigments ameliorate oxidative stress responses - one of the most significant environmental challenges encountered by MCF - using the model rock fungus Knufia petricola (Chaetothyriales) strain A95.
The manuscript of the History of Outremer by William of Tyre stored at the BNF (ms. fr. 9084) is believed to have been illustrated by two different hands. Indeed, the first five miniatures of this manuscript appear to be very different from the last seventeen, which were supposedly painted by an artist known as the "Hospitaller Master". This painter worked on at least two manuscripts in Paris between 1276 and 1280, and eight more in Saint Jean d'Acre before 1291. During his stay in the Latin Kingdom of Jerusalem, his palette changed and reached its most important development in the Manuscript of the History of Outremer, maybe influenced by the colourful crusader style of the first five miniatures. The present work aims at identifying the pigments used on both parts of the manuscripts and see whether they are the same for both artists or not. For that, portable XRF analysis was used directly at the Bibliothèque National de France in Paris, where the manuscript is stored. This allowed a quick, non destructive and non invasive study of the manuscript. Significant differences were observed in the compositions of some pigments indeed, in particular for the red and green, showing the use of different palettes. This could indicate that the Hospitaller Master not only brought his knowledge and style, but also probably part of his palette of pigments with him when moving to Saint Jean d'Acre.
Black ascomycetous microcolonial fungi (MCF) are persistent inhabitants of rock surfaces in deserts as well as ubiquitous in other wide-spread terrestrial ecosystems including man-made materials such as solar panels. The ability of MCF to cope with multiple, rapidly fluctuating stresses makes the group an interesting subject in the study of stress resistance. Carotenoids and melanin are amongst the protective pigments that contribute to the robustness of MCF. We studied their role in stress resistance of the non-pathogenic rock-inhabiting fungus Knufia petricola (Chaetothyriales) strain A95. Disruption of melanin synthesis affects not only oxidative-stress resistance but also the extracellular polysaccharide (EPS) matrix and lipid composition of the cell membrane.
Biocides are commonly applied to building materials such as renders and paints in order to protect them from microbial spoilage. Since the building materials are commonly exposed to weathering conditions, biocides incorporated within the material matrices tend to leach out during the rain events. Moreover, photodegradation processes play an important role in the fate of biocides, due to the exposure to natural sunlight. Leaching of biocides and their moderate persistence, indicate that photodegradation products of biocides can also be found as environmental contaminants in runoff waters. In this study we investigated the photodegradation of four commonly used biocides (carbendazim, diuron, octylisothiazolinone and terbutryn) in four different paint formulations with selected pigments (red, white, black and one artificial, not commercial pigment-free formulation for comparison). As pigments interact with the spectrum of the incoming light, the effect of pigments on photodegradation rates was assumed to be relevant.
Samples were prepared by painting 2 layers of selected paints on glass plates. The dry paint samples were exposed to UV light for designated time periods ranging from 0 h to 1056 h of total exposure time in a commercial UV-Test® Fluorescent / UV Instrument (Atlas Material Testing Technology, Illinois, USA). The applied energy was 1.2 W/m2. The black panel temperature was established at 40 ºC. The radiant energy from the UV fluorescent lamps was concentrated in the wavelength region at 351 nm and below. All samples were prepared in triplicates. After irradiation, paint samples were removed from glass carriers and extracted with methanol. The remaining biocide concentrations as well as the amounts of photodegradation products were analysed with the use of liquid chromatography coupled to mass spectrometry.
The transparent, pigment-free formulation was the most vulnerable to light exposure, a visible colour change from white to yellow was observed after 1056 h of irradiation. Diuron, octylisothiazolinone and terbutryn degraded from pigment-free formulation following first-order degradation kinetics. A decrease of carbendazim was also observed. The remaining formulations showed similar degradation patterns for all analysed biocides. All paints showed degradation for octylisothiazolinone with 3-octyl-2(3H)-thiazolone being the main product for red, white and black pigment paint. N-octylacetamide and N-octyloxamic acid were dominant in the pigment-free formulation. Terbutryn sulfoxide was the main degradation product of terbutryn in case of the white paint, while other pigments showed higher concentrations of desbuthyl-2-hydroxy-terbutryn and desethyl-2-hydroxy-terbutryn.
A determination of photodegradation in terms of pigment type, measured light spectra and intensity as outlined in this study, could provide a basis for establishing a quantitative description of the fate of biocides in paints, which has significance not only in terms of environmental science, but also could provide a guideline for developing new and effective products.
Z02 is one of the three technically supporting projects at the CSMC. In collaboration with Z01 and Z03, it aims at bridging the gap between humanities and natural sciences and technology. To that purpose, we set up a laboratory with a range of high-end instruments, most of them mobile, allowing thorough non-destructive analysis of manuscripts. In addition to working on constantly improving the laboratory and the methods of analysis, a substantial part of our activities is dedicated to service, by supporting different research projects conducted at the center.
In this talk, we will present our equipment and the possibilities offered by the different techniques available regarding the different kinds of missions: typology and classification of inks, provenance studies, recovery of faded inscriptions and palimpsests, reconstruction of the history of manuscripts, authentication and dating. We will give a brief overview of our past and ongoing activities in the frame of the second phase of the CSMC. Finally, a selection of three projects will be presented in greater detail to highlight the possibilities of our laboratory and the diversity of missions which can be carried out:
- Support of project C08 on East Frankish manuscripts containing collections of formulae
- Identifying color materials applied in Muhammad Juki's Shahnamah with non-invasive combined methods
- Checking for the presence of metals in the Herculaneum papyri
A non-invasivemethod has been carried out to show the capabilities and limitations of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for identifying of colourants and binders in modern reverse glass paintings. For this purpose, the reverse glass paintings “Zwei Frauen am Tisch” (1920–22), “Bäume” (1946) (both by Heinrich Campendonk), “Lofoten” (1933) (Edith Campendonk-van Leckwyck) and “Ohne Titel” (1954) (Marianne Uhlenhuth), were measured. In contrast to other techniques (e.g. panel and mural painting), the paint layers are applied in reverse succession. In multi-layered paint systems, the front paint layer may no longer be accessible. The work points out the different spectral appearance of a given substance (gypsum, basic lead white) in reverse glass paintings. However, inverted bands, band overlapping and derivative-shaped spectral features can be interpreted by comparing the spectra fromthe paintingswith spectra frompure powders and pigment/linseed oil mock-ups. Moreover, the work focuses on this method's capabilities in identifying synthetic organic pigments (SOP). Reference spectra of three common SOP (PG7, PY1, PR83) were obtained from powders and historical colour charts.We identified PR83 and PY1 in two reverse glass paintings, using the measured reference spectra. The recorded DRIFTS spectra of pure linseed oil, gum Arabic, mastic, polyvinyl acetate resin and bees wax can be used to classify the binding media of the measured paintings.