Characterization of proteins in paint media by immunofluorescence. A note on methodological aspects

Abstract

A protocol for the characterization of proteins in paint media by immunofluorescent labelled antibodies is proposed. The main difficulties of the technique and their possible solutions are discussed. Positive results on egg white, in model samples, are reported.     

The Restoration of the ‘Vienna Dioscorides’

Abstract

Very small paint samples from Cosimo Tura's ‘The Annunciation with Saint Francis and Saint Louis of Toulouse’ were submitted to amino acid analysis in order to determine the nature of the binding media. The four panels appeared to have been painted with egg tempera, and showed extensive localized deterioration in the blue areas but not in the other coloured areas. Following the Picotag method, the samples were hydrolyzed in an acid vapor, derivatized with iso-thiocyanatobenzene, and analyzed using reversed phase high pressure liquid chromatography (HPLC). Amino acid analysis demonstrated that the red and brown areas were painted using egg yolk as the binding medium, while the blue areas were painted with animal-skin glue (distemper). Analysis of the green paint indicated a mixture of egg yolk and glue. The use of these techniques makes it possible to identify proteinaceous materials in art objects from samples in the microgram range.     

Two Stangengläser from the collection of the Museum of Decorative Arts in Prague: Decorative techniques,material analyses,and conservation

Abstract

The two Stangengläser, tall cylindrical vessels from the beginning of the seventeenth century, are described in detail. The severely damaged Stangengläser, decorated with diamond-point engraving and cold-painting, were challenging to treat. Research preceding the conservation revealed differences in decorating techniques. Samples of the paint layers were analyzed using micro-Fourier transform infrared spectroscopy. Two layers of resinous varnish with a middle layer of paint containing a plant gum were found on the Stangenglas with Allegory of Caritas and Zierotin coat of arms. In the plain paint layer of the Stangenglas with dancing couples, egg white was identified as the binder. The glasses, analyzed using scanning electron microscopy with energy dispersive X-ray spectrometry, had similar potash–lime–silica compositions, which seems to be characteristic for glass from Bohemian lands. Results of analysis contributed to the discussion about the possible provenance of the Stangengläser, the glassworks at Wilhelmberg, South Bohemia.     

La technique des «Primitifs flamands»

Abstract

For the study of Italian paintings and their techniques the examination of the binding media (glue, egg, oil) has considerable importance, but with the usual scientific methods of analysis the results have never been conclusive. Each sample may include more than one layer of paint and many constituents; egg yolk alone contains protein, oils, cholesterol. In the present project, in order to identify these diverse materials and also to eliminate interference from contamination (glue, wax or oil) used in later restoration processes, it was decided to mount original paint samples, including a bit of the ground, as cross-sections in a polyester resin embedding material and then to make the constituents visible under the microscope by using selective staining techniques. Only in this way could the foreign materials be distinguished from the original and the structure of the original layers be understood. Finally, other tests such as the fluorescent antibody technique and thin-layer chromatography could be applied to confirm the results of the staining. In removing over 500 specimens fronl paintings in the Walters Art Gallery precautions were taken to assure sample authenticity, and during the testing at the University of Michigan careful methods of standardization and control were devised, using both fresh and old samples of egg tempera and oil. Two stains, Ponceau S for protein and Sudan Black B for oil, provided the most workable means of identifying the binding media in the majority of the samples studied. A final report will have to await correlation of the material, but certain observations may be made at this stage: (a) 14th century, in primarily tempera paintings a limited use of oil was found associated with a specific green pigment, copper resinate; (b)15th century, the majority of the paintings were entirely of egg tempera, but layers containing oil in the underpainting or in the above-mentioned copper green occurred more frequently; (c)16th century, egg tempera was not replaced by oil, but both were used in a complex layering technique, the media varying layer by layer and area by area; (d)17th century, the mixed technique gradually declined, but egg tempera continued to be associated with the painting of flesh and occasional highlights.     

Climatically Induced Degradation Processes in Conserved Archaeological Wood Studied by Time-lapse Photography

ABSTRACT

Samples of conserved archaeological wood of different ages, origins, and conservation histories were aged in a climate chamber for seven months, while the humidity alternated between 30% RH for 12 hours and 80% RH for 12 hours at a constant temperature of 30°C. Photographs were taken once every hour, which enabled the creation of a time-lapse movie. Some samples degraded visibly, whereas others were unaffected. Most of the samples were robust and would be able to survive well even in a very poor museum climate. Among the sensitive samples, three types of degradation were identified, namely disintegration, pyrite oxidation, and efflorescence of white crystals. Disintegration was ascribed to dimensional changes caused by the RH alternations in very fragile wood. The white efflorescence was interpreted as the recrystallization of an alum-associated substance, possibly mercallite (KHSO₄). The pyrite oxidation was observed as the efflorescence of a thick yellow, grey, and green powder. Characterization of selected samples was performed using X-ray fluorescence spectrometry, X-ray diffraction spectrometry, scanning electron microscopy with energy dispersive X-ray spectroscopy, inductively coupled plasma – optical emission spectroscopy, Fourier transform infrared spectroscopy, ionic conductivity – liquid chromatography, and pyrolysis-gas chromatography-mass spectrometry with in situ silylation using hexamethyldisilazane.     

TOXICITY OF BENZOTRIAZOLE

Abstract

Blue and white Chinese porcelain specimens from Dehua and Zhangzhou kiln sites from the Ming dynasty (AD 1368–1644), and Jingdezhen kiln sites from the Yuan (AD 1280–1368) to Ming dynasties were collected. The chemical compositions of these valuable samples were determined using energy dispersive X-ray, fluorescence (EDXRF) spectrometry, a non-destructive method, and some Jingdezhen samples were analyzed by scanning electron microscopy and transmission electron microscopy. The EDXRF results were subjected to correspondence analysis. Differences in the composition of the specimen bodies were found for specimens from different production sites. The blue and white Jingdezhen imperial, porcelain from the Yuan to Ming dynasties can be divided into two periods based on differences in the chemical composztion and microstructure of the pigments. The reasons for these variations are discussed.     

STORAGE OF ARCHAEOLOGICAL TEXTILE FINDS IN SEALED BOXES

Abstract

A white deposit was observed on the glass lids of boxes used to store archaeological textile fragments for some 40 years. It was identified as sodium formate formed from formaldehyde given off by cardboard in the boxes. Heavy metal ions in some samples of the deposit originated, via the textile fragments, from corroded bronze ornaments in the graves.     

Whiteness feels good here: interrogating white nationalist rhetoric on Stormfront

ABSTRACT

This essay adopts a critical rhetorical perspective attuned to affect to investigate white nationalist rhetoric on Stormfront, a popular white nationalist message board. My analysis illuminates how Stormfront attempts to appeal to mainstream white audiences by resisting normative expectations and affects articulated with white supremacy and (re)constructing white nationalism as a formation of white racial consciousness articulated with communal belonging, common sense, and pride. On Stormfront, affect is mobilized discursively to challenge colorblindness, construct rhetorical distance between white nationalism and white supremacy, and strategically negotiate white (dis)comfort with direct discourse on race to compel affective investments in white nationalism.     

Sampling Instruments

Abstract

systematic study of the whole thickness of the ground was carried out on about 50 paintings. The originality of the work consisted in first revealing by back -scattered scanning electron microscopy where two types of coating had been used. The components of each layer were then analyzed by X-ray diffraction and found to be principally anhydrite for the gesso grosso and gypsum for the gesso sottile. According to these results, Tuscan painters used a double white ground until the end of the fifteenth century. The use of a single layer of gypsum was widespread in other Italian schools in the fifteenth century.     

Material for a History of Conservation

Abstract

The non-saponifiable fractions of the principal drying oils have been examined by gas and thin-layer chromatography and found to be qualitatively similar though varying in the relative amounts of sterols present. In the case of aged paint films it has been found that these sterols have largely disappeared from unpigmented films and those containing light red and lead white as pigment, though they survive quite well in the presence of verdigris. Similarly cholesterol was not found to survive well in egg tempera films. Doubt is felt as to the value of such analyses as an approach to paint medium identification.     

Masonry mortars in the Castillo de San Felipe del Morro,San Juan,Puerto Rico: a method for categorization

Abstract

This paper describes the study made of mortars used in the Castillo de San Felipe del Morro in San Juan, Puerto Rico. Through a multi-disciplinary approach, combining examination of materials in situ and in the laboratory with a study of archival documents, a relatively simple system of categories was devised. Mortars were grouped into three categories based on overall color and composition: red/beige, white, and brick-dust. The information gleaned in this study served as a basis for a condition assessment and will be used for developing replacement mortars.     

Wall Coating Using the Escariola Technique

Abstract

This paper is concerned with the rediscovery of a technique of interior wall decoration known as Escariola which was introduced by Austrian and Italian immigrants to the mid-west region of the state of Santa Catarina (southern Brazil) at beginning of the twentieth century. This coating provides a refined, attractive and durable finishing. Historical investigation combined with sample characterization using X-ray diffractometry (XRD) and differential thermal and thermogravimetric analyses (DTA/TGA) revealed that this technique consists of the application on a rendered masonry wall of a 2–3 mm thick layer of slaked lime/white cement paste which is subsequently polished with talcum powder. Samples of Escariola paste were empirically reformulated and tested on a rendered masonry wall. Guidelines for producing Escariola are proposed here.     

Determining The Presence of Photocatalytic Titanium White Pigments via Embedded Paint Sample Staining: A Proof of Principle

ABSTRACT

Twentieth century paints often contain titanium dioxide and zinc oxide based white pigments that can range from photostable to highly photocatalytic. Photocatalytic pigments can cause the degradation of paint upon UV exposure, whereas photostable pigments may be benign or can protect paintings from degradation. Hence, knowing whether or not a pigment is photocatalytic is of high importance for risk assessment and the subsequent decision making process concerning storage and exposure conditions of objects. Here we present a proof of principle, focused on titanium white paints, for an easy-to-use and low-tech application of a commercial photocatalytic activity indicator ink (PAII) on embedded paint samples or cross sections. This test determines, qualitatively, if a photocatalytic pigment is present in a white paint sample. The PAII paint sample staining application shows an obvious color change, within five minutes of UV irradiation, for paint samples containing photocatalytic pigments. A microscope with a camera and a UV source are the only necessary equipment for the application of this method. A quantitative image processing protocol is also proposed as an extension of the staining method by applying open source software analysis to measure the color change using photographs. The test was evaluated on reference paints with well-characterized pigments and applied on samples from modern paintings by Piet Mondriaan, Robert Ryman, and Lucebert, indicating the presence of harmful photocatalytic pigments in these cases. The novel application of a commercial ink on paint samples offers a simple test, not just for assessment of photocatalytic activity of titanium white pigments, but which may in future be applied for the detection of photoactive forms of zinc white and other potentially harmful semiconductor pigments in art objects.     

Can a non-Muslim Mass Shooter be a “Terrorist”?: A Comparative Content Analysis of the Las Vegas and Orlando Shootings

ABSTRACT

This study used the 2017 Las Vegas and 2016 Orlando mass shootings as case studies to explore alleged double standards in reporting of events featuring Muslim and non-Muslim mass perpetrators of violence. The study used framing theory and content analysis to examine Los Angeles Times and New York Times coverage of the shootings during the one week immediately following each event. Findings are consistent with previous literature and the researchers’ expectations. The Orlando shooting, carried out by a Muslim, was allotted more coverage despite the fact that it produced nine fewer fatalities than the Las Vegas shooting, perpetrated by a white non-Muslim. The analysis also showed that the examined newspapers were more likely to employ a “terrorism” frame in their coverage of the Orlando shooting than in their coverage of the Las Vegas shooting; link the Orlando mass shooting with the global war on terrorism; and to humanize Stephen Paddock, the white perpetrator of the Las Vegas shooting. Framing differences found in this study may contribute to downplaying the threat of white male gun violence, and to reinforcing fears of Islam and Muslims.     

TWO ABORIGINAL ROCK ART PIGMENTS FROM WESTERN AUSTRALIA THEIR PROPERTIES,USE, AND DURABILITY

Abstract

Naturally occurring pigments used by Aborigines in rock paintings have been collected in Western Australia. They area red pigment (mainly hematite, Fe₂O₃)(from a red ochre mine worked until historic times by Aborigines, and a white pigment (huntite, Mg₃Ca(CO₃)₄) which is still collected and used by Aborigines. Samples were also taken from rock paintings in which these pigments were used or were thought to have been used. The pigment samples were analysed to establish chemical, mineralogical, and physical properties. The paint samples were examined microscopically and with an electron probe to study their relationship with the rock surface and with other paint layers. The relationship between the pigments’ properties and their durability is discussed.     

Microbial calcification of gypsum-rock and sulfated marble

Abstract

A broth containing the sulfate reducing bacterium Desulfovibrio desulfuricans was used to treat samples of reagent calcium sulfate, gypsum-rock specimens, fragments from a marble monument with a black weathering crust rich in gypsum, and a marble monument with similar crust. Calcite was found to have formed on all treated surfaces suggesting that this microbe has the potential to clean crusted marble monuments whilst also regenerating calcite, the parent mineral of the marble.     

Lead White or Lead Whites? Reconsideration of Methods of sefidāb-i-sorb Production in Iran

Lead white is widely used as a white pigment in the history of Persian painting. This paper focuses on three Persian treatises dated between the twelfth and the sixteenth century, which explained different manufacturing methods of lead white or sefidāb-i-sorb. Experimental reconstruction of each recipe to access the comprehensive meaning of the text and analytical studies with X-ray powder diffraction on products of recipes revealed white compounds other than the previously known products of hydrocerussite (Pb(OH)₂?·?PbCO₃) and cerussite (PbCO₃) in samples. Chlorine-containing raw materials mentioned in these recipes lead to the chemical products of laurionite (Pb(OH)Cl), blixite (Pb₈O₅(OH)₂Cl₄), and phosgenite (Pb₂Cl₂(CO)₃) in the final products. These data lead to the hypothesis of the discrepancy of the lead white pigment between Iran and Europe and a marked probability of other compounds in historic Persian lead white samples.     

THOMAS BARDWELL AND HIS PRACTICE OF PAINTING: A COMPARATIVE INVESTIGATION BETWEEN DESCRIBED AND ACTUAL PAINTING TECHNIQUE

Abstract

Thomas Bardwell (1704–67), an English portrait painter, wrote a technical treatise entitled The Practice of Painting and Perspective Made Easy which was published in 1756. The section on painting deals exclusively with the oil technique and may be considered one of the most original productions of its kind written in England. A total of 153 paint samples were taken from 15 of Bardwell’s paintings dating between 1740 and 1766, the better part of his active career. Through cross-sections, and likewise numerous analyses, made from these paint samples it was possible to reconstruct Bardwell’s actual practice. This in turn could be compared with the suggested technique as explained in his book. Bardwell’s actual practice follows his written advice rather closely; however, in general it was discovered to be less complicated.     

Evaluating Single- and Two-Constant Kubelka-Munk Turbid Media Theory for Instrumental-Based Inpainting

Abstract

Instrumental-based color matching using non-destructive reflection spectrophotometry can be used as an aid in pigment selection for inpainting. This is useful when metamerism is of concern, particularly in modern art where the number of colorants available to artists and conservators is quite large. Simplified methods have been developed for art conservation where a single tint of each pigment mixed with white is required to define a pigment's optical properties based on the single-constant form of Kubelka-Munk (K-M) turbid media theory. Theoretically, this simplification can lead to errors in pigment selection for dark colors and colors not containing a white pigment. Instead, the two-constant form of K-M theory can be used where the model assumptions more closely match the optics of inpainting materials. The two methods were compared using four acrylic emulsion paints with a range of pigment absorption and scattering properties. It was found that the simplified method was inadequate for paints with appreciable and spectrally selective scattering, and as a consequence, pigment selection may result in a greater number of pigments than actually required. It was also found that only two samples per pigment were required to implement the two-constant technique: the mass tone and a tint.