The Age- Embrittlement of Silver Coins

Abstract

Conservation treatments of three modern paintings are presented which illustrate the use of Beva 371 in solving difficult and varied conservation problems. They were selected as representing cases which could not have been solved satisfactorily with other adhesives and are: 1. Gottlieb, oil on glue-sized cotton. Transparently lined with Mylar; 2. Balthus, casein on unprimed canvas. Mounted on a solid support; 3. Klee, gouache on decaying, unprimed burlap. Transparently lined on silk chiffon.     

The conservation and iconography of Viceregal paintings and sculpture: old problems and new approaches

Abstract

The reasons for the often poor condition of Viceregal paintings and sculptures are examined. The conservation of four works is described, chosen largely because they had typical problems and would benefit from recently developed techniques. The treatments were: the preliminary lining of very cupped paintings, before using moisture to stretch the original canvas and allow the paint layer to lie flat again; lining badly torn paintings on a thin, semi-rigid, transparent support and using the old stretcher, in order to preserve the structure and aesthetic impression of the painting as much as possible; masking to protect susceptible fine lines against solvent action during cleaning; blending disturbing passages of the paint layer like blanching, irreducible stains, singeing and pentimenti into the colour scheme without overpainting; repairing broken pieces of sculpture with bamboo dowels. The study is accompanied by an iconographical discussion of colonial works of art.     

A Review of Lining Methods for Paper-based Photographic Prints from the Nineteenth and Twentieth Centuries

Abstract

A photograph may be lined when its physical condition is so poor that an additional support is necessary to ensure its survival. Photographic prints may comprise a number of layers, often composed of dissimilar materials that react differently to moisture. As most traditional lining methods involve the use of water, lining can thus cause stresses within and between the various layers. These stresses are thought to exhibit as increased cracking of binder layers and increased curling of the photograph itself. This paper reviews the literature to date regarding the lining of photographs and examines possible future treatment pathways. From the literature, it would appear that the question of how best to line traditional photographic formats, such as albumen, collodion and silver gelatin prints, has not yet been answered. Standard water-based lining adhesives can cause damage to various types of traditional photographs. Heat and solvent-activated adhesives can also cause damage; however, they may allow better control over the physical changes that occur within some types of photographs during treatment. Further investigation of non-traditional adhesives for paper (e.g. waxes and synthetic polymers) is recommended.     

The Effect of Changes in Environmental Conditions on the Mechanical Behaviour of Selected Paint Systems

ABSTRACT

The impact of relative humidity (RH) and temperature variation on the mechanical behaviour of paintings on canvas was investigated, based on the various environmental recommendations that are applied by museums and institutions worldwide. Paint samples were constructed based on the works of twentieth-century artists such as Soulages and Riopelle. The various samples are based on criteria such as paint media, additives, pigment type, canvas type, thickness, type of application, and drying time. Once they are fully dry, paint films behave as elastic, viscoelastic, or viscoplastic materials depending on the chemical nature of their components. These properties, as well as tensile strength, were determined by a series of tensile tests. Other samples were included, originating from discarded oil paintings on canvas from the seventeenth and nineteenth centuries. To carry out mechanical tests under controlled conditions of temperature and RH, a climatic chamber was built around the column of a universal testing machine. Samples were submitted to stress relaxation tests to observe their response to changes in environmental conditions. RH was increased from 20 to 90% and temperature from 15 to 60°C. Reactivity diagrams were drawn based on the results. The endurance limit under mechanical fatigue was determined from the diagrams and helped define the risks associated with each painting type when exposed to the accepted environmental recommendations.     

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.     

4 LEAD-TIN YELLOW

Abstract

The proper preparation and application of Paraloid B-72 make it an excellent adhesive for archaeological ceramics and other materials. An understanding of the principles of adhesion is essential to the successful application of solvent adhesives.     

Original and reformulated BEVA® 371: Composition and assessment as a consolidant for painted surfaces

Abstract

Many natural and synthetic products have been used for the consolidation of paint layers, but none have been thoroughly tested for this application. This is apparent for most of the synthetic and semi-synthetic adhesives for conservation, many of which are pure polymer resins and dispersions adapted from other industries. They were not specifically formulated with the appropriate properties for conservation, nor do they take advantage of some of the more recent developments in adhesive technology. BEVA^® 371 is unique among adhesives used for consolidation treatments, as it is a multi-component mixture and was designed specifically for the conservation field using the best technology available at the time. However, the main focus of the research was its application as a lining adhesive. Thus, optical properties and stability, specifically color stability, were not thoroughly evaluated even though some lining applications that were first recommended could have benefited from this type of investigation. This paper will discuss the development of BEVA^® 371, the chemistry, and roles of each component, and address a practical concern about the tack behavior of its replacement formulation, BEVA^® 371b.     

The Use of Moisture Barriers on Panel Paintings

Abstract

Deterioration of paintings is effected by chemical, physical and biological agents. Activity of these agents generates mechanical stresses which result in cracking, cupping, cleavage and flaking of the paint film. Internal mechanical stress appears to be primarily responsible for premature or drying cracks in paint. Stresses external to the paint cause age cracks which penetrate both paint and ground. The literature explaining the origin and characteristics of these cracks is reviewed. Although premature cracking can only be avoided by instructing the artist in proper use of materials, age or mechanical cracking can presently be prevented by environmental controls and careful handling. Present methods of reinforcement of paintings in general only partially stabilize them against environmentally generated stresses. Further research appears necessary for more complete understanding of the stresses old paint can withstand and of the forces exerted by the shrinking and swelling of textile and wooden supports. Search for and testing of more physically and chemically inert support materials are suggested.     

Preliminary tests for mechanical properties of wooden ‘buttons’ used for attaching auxiliary supports behind panel paintings

Abstract

When wooden supports of panel paintings have been severely altered or damaged and the original cross beams are missing, new cross beams or other types of auxiliary supports are connected to the panel's back-face in order to achieve desired effects including panel strengthening and control of deformations. Some conservation laboratories use small wooden blocks, each glued on the back face of the panel and holding freely the head of a screw connected (often by means of springs) to the auxiliary support; such blocks being called in Italian ‘piedini’ or ‘bottoni’, the English term ‘buttons’ is proposed here. This paper reports research aiming to characterize the mechanical behavior of three types of ‘buttons’ having different geometries and made of various wood types (oak, walnut, lime, beech, and a medium density fiberboard). Short-term mechanical tests (～1 minute duration) were performed with a universal testing machine by axially pulling out the 4 mm diameter steel screw from the button, glued onto a dummy board. Load and deformation were recorded, and the load–deformation curves were analyzed. The results show that the deformability and the load-carrying capacity of the buttons were influenced primarily by the manufacturing geometry and secondarily by the wood density.     

General remarks on the painting technique of Velazquez and restoration carried out at the Museo del Prado

Abstract

The collection of paintings by Velázquez in the Museo del Prado is important both because of the number of works — about 50 — and because of their quality and significance. It includes the Feast of Bacchus (The Drunkards), the Forge of Vulcan, Christ on the Cross, the Surrender of Breda (The Lances), the Fable of Arachne (The Spinners), Las Meninas and various royal portraits. Most of these works are in very good condition, which is essential for a proper study of the painter's technique and his development; in addition, since their source is the royal collection, they are well documented. Since 1982 most of the works by Velázquez in the Museo del Prado have been submitted to technical examination and to restoration. The technical studies included X-radiography, infrared reflectography, and analysis of the supports and materials, allowing us to establish the characteristics of each painting (technique, changes in composition, condition, history) and the development ofthe artist through the changes in his technique. Restoration consisted basically of consolidating the paint layers, moderate cleaning and the inpainting oflacunae. The only exception to the general good condition of the paintings was The Spinners, which presented a serious problem of craquelure and lack of adhesion in the paint layer.     

Copper vanadate minerals found in mediaeval mural paintings

Abstract

A yellowish copper vanadate mineral has been found in Swedish mural paintings from the fifteenth century. Small patches occur in malachite-green paint. Thirteen samples from five churches have been analyzed by optical and scanning electron microscopy with energy–dispersive X-ray spectrometry, transmission electron microscopy, X-ray powder diffraction, and polarized light microscopy. The substance is evidently the rather uncommon mineral volborthite, with the chemical formula Cu₃V₂O₇(OH)₂.2H₂O. Very small quantities have also been noted for another mineral, presumably calcio-volborthite, CaCu(VO₄)(OH), also named tangeite. The results show that the conservator should always be observant for pigments not earlier noticed or reported. There are some old mines in Central Europe, e.g. in Germany, which contain malachite as well as copper vanadate minerals, and this is probably the origin of the yellow patches in the paintings.     

Radiocarbon dating of canvas paintings: two case studies

Abstract

Well-cleaned canvas fibres from two oil paintings have been dated by radiocarbon. Although the dates agree with the expected ages of the paintings to a first approximation, uncertainties in the date arise from ambiguities (or ‘wiggles’) in the calibration curve. Only by introducing additional information about the paintings into the calculations can more precise results be obtained. Two paintings have been dated in this way, using the radiocarbon dating technique in conjunction with dendrochronological and art historical information.     

Search methods for prognostic factor systematic reviews: a methodologic investigation

Objective:This study retroactively investigated the search used in a 2019 review by Hayden et al., one of the first systematic reviews of prognostic factors that was published in the Cochrane Library. The review was designed to address recognized weaknesses in reviews of prognosis by using multiple supplementary search methods in addition to traditional electronic database searching.Methods:The authors used four approaches to comprehensively assess aspects of systematic review literature searching for prognostic factor studies: (1) comparison of search recall of broad versus focused electronic search strategies, (2) linking of search methods of origin for eligible studies, (3) analysis of impact of supplementary search methods on meta-analysis conclusions, and (4) analysis of prognosis filter performance.Results:The review''s focused electronic search strategy resulted in a 91% reduction in recall, compared to a broader version. Had the team relied on the focused search strategy without using supplementary search methods, they would have missed 23 of 58 eligible studies that were indexed in MEDLINE; additionally, the number of included studies in 2 of the review''s primary outcome meta-analyses would have changed. Using a broader strategy without supplementary searches would still have missed 5 studies. The prognosis filter used in the review demonstrated the highest sensitivity of any of the filters tested.Conclusions:Our study results support recommendations for supplementary search methods made by prominent systematic review methodologists. Leaving out any supplemental search methods would have resulted in missed studies, and these omissions would not have been prevented by using a broader search strategy or any of the other prognosis filters tested.

Open in a separate windowLeah Boulos     

Using genderize.io to infer the gender of first names: how to improve the accuracy of the inference

Objective:We recently showed that genderize.io is not a sufficiently powerful gender detection tool due to a large number of nonclassifications. In the present study, we aimed to assess whether the accuracy of inference by genderize.io can be improved by manipulating the first names in the database.Methods:We used a database containing the first names, surnames, and gender of 6,131 physicians practicing in a multicultural country (Switzerland). We uploaded the original CSV file (file #1), the file obtained after removing all diacritic marks, such as accents and cedilla (file #2), and the file obtained after removing all diacritic marks and retaining only the first term of the compound first names (file #3). For each file, we computed three performance metrics: proportion of misclassifications (errorCodedWithoutNA), proportion of nonclassifications (naCoded), and proportion of misclassifications and nonclassifications (errorCoded).Results:naCoded, which was high for file #1 (16.4%), was reduced after data manipulation (file #2: 11.7%, file #3: 0.4%). As the increase in the number of misclassifications was small, the overall performance of genderize.io (i.e., errorCoded) improved, especially for file #3 (file #1: 17.7%, file #2: 13.0%, and file #3: 2.3%).Conclusions:A relatively simple manipulation of the data improved the accuracy of gender inference by genderize.io. We recommend using genderize.io only with files that were modified in this way.     

NOTES ON THE USE OF A VACUUM HOT-TABLE FOR TEXTILES

Abstract

A miniature low-pressure apparatus for localized treatment of paintings is described. Alternative working surfaces are available which allow heat and moisture treatment on canvas paintings without removal from their stretchers. Other applications of the apparatus are discussed.     

THE USE OF AN INFRA-RED IMAGE-CONVERTER FOR THE EXAMINATION OF PANEL PAINTINGS

Abstract

The use of an S-1 response infra-red image-converter for the examination of panel paintings is described. It is shown that satisfactory results maybe obtained with this equipment, which is easy to operate. The examination of underdrawings, retouchings and pentimenti is briefly discussed.     

The Stabilizing of Wood found in the Viking Ship of Oseberg—Part II

Abstract

Although smalt, a glass, might be expected to behave as a stable pigment, discolouration of smalt-containing paint layers has been observed. Early references from the literature are cited which mention the discolouration of smalt in oil media. Originally blue layers on paintings have changed into dull grey or greyish-green. Experiments suggest the following factors for this discolouration: low refractive index of the pigment compared with that of oil media; interaction of alkali content or cobalt content with oil and oleo-resinous media; the possibility of similar reactions with resin- or oil-resin varnishes in certain conditions. Discolouration may also occur if smalt is mixed with other pigments, or added as a drier or as an adulterant.

A proper understanding of the mechanism of the deterioration would require further research by more sophisticated methods.     

Distribution of moisture in reconstructed oil paintings on canvas during absorption and drying: A neutron radiography and NMR study

Moisture is a driving factor in the long-term mechanical deterioration of canvas paintings, as well as for a number of physico–chemical degradation processes. Since the 1990s a number of publications have addressed the equilibrium hygroscopic uptake and the hygro-mechanical deformation of linen canvas, oil paint, animal glue, and ground paint. In order to visualise and quantify the dynamic behaviour of these materials combined in a painting mock-up or reconstruction, we have performed custom-designed experiments with neutron radiography and nuclear magnetic resonance (NMR) imaging. This paper reports how both techniques were used to obtain spatially and temporally resolved information on moisture content, during alternate exposure to high and low relative humidity, or in contact with liquids of varying water activities. We observed how the canvas, which is the dominant component in terms of volumetric moisture uptake, absorbs and dries rapidly, and, due to its low vapour resistance, allows for vapour transfer towards the ground layer. Moisture desorption was generally found to be faster than absorption. The presence of sizing glue leads to a local increase of moisture content. It was observed that lining a painting with an extra canvas results in a damping effect: i.e. absorption and drying are significantly slowed down. The results obtained by NMR are complementary to neutron radiography in that they allow accurate monitoring of water ingress in contact with a liquid reservoir. Quantitative results are in good agreement with adsorption isotherms. The findings can be used for risk analysis of paintings exposed to changing micro-climates or subjected to conservation treatments using water. Future studies addressing moisture-driven deformation of paintings can make use of the proposed experimental techniques.     

Evaluation of system performance of near-infrared imaging devices

Abstract

A method is described for the evaluation of the performance of near-infrared imaging devices to detect underdrawing and reworking of paintings. System analyses have been performed on two different ' near-infrared imaging devices: a Hamamatsu lead sulphide vidicon camera and a Photometries silicon charge coupled device (CCD) camera. The analyses included modelling of the system spectral response curve by analysis of the system components, as well as considering the limiting resolution and modulation transfer function (MTF). The modelling was confirmed by examination of a test panel at various wavelengths. Calculation of visibility is introduced as a quantitative measure of system performance. This calculation is also discussed as a means to define more clearly the actual performance requirements of these systems. This analysis has revealed the strengths and weaknesses of current systems, and provides guidance in the construction of improved devices.