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.     

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.     

Hydrogen plasma reactions in a d.c. mode for the conservation of iron meteorites and antiquities

Abstract

Four iron meteorite fragments and 13 archaeological iron objects were exposed to a lowpressure hydrogen plasma for up to two weeks in a pilot apparatus. In the experiment the objects acted as cathodes in a 600–1600V d.c. electrical field. While the chlorine-containing β-FeOOH, akaganeite, was present in all objects before the test, no akaganeite and no chlorides were present afterwards. The objects, including one meteorite which had been exposed for more than 5000 years to seawater, were found to be stable after the glow discharge treatment. The major mineral after treatment was identified as magnetite, and the objects generally assumed an iron-grey surface colour. No sputtering and no reduction to free iron took place under the test conditions, operating at or below 120°C and at pressures of O·4–1mb hydrogen.     

Street art conservation in Athens: Critical conservation in a time of crisis

Street art, public murals, and graffiti are forms of contemporary art which flourish in the urban environment. The current socioeconomic and political crisis in Greece has rendered Athens a living city canvas that attracts artists, art lovers, young people, tourists, journalists, and photographers. The conservation of street art in extreme outdoor conditions is a new area of interest for conservation research and practice. Since 2010 the Conservation of Wall Paintings Laboratory of the Department of Conservation of Antiquities and Works of Art (CAWA) of the Technological Educational Institute (TEI), Athens has been engaged in a project to explore ethics, carry out documentation, and initiate new research into street art and its conservation. Since 2012, Street Art Conservators (St.a.co.), a team comprising academics, conservators, and students from CAWA has worked in the streets of Athens for the preservation of street art. The protection and conservation of street art require the creation of a critical mass of people who are interested in the study and preservation of street art, co-operative conservation work and research, and the documentation and digital mapping of street art as an alternative means for its preservation.     

Extraction of Zinc Corrosion from Beneath a Paint Layer: A Case Study

ABSTRACT

Conservation of an oil painting on a zinc support is a complex challenge that has not been covered in the literature. Oil paint and zinc support rarely form a working combination because of their chemical properties. This article discusses the conservation of an oil painting on a zinc support that was found in extremely bad condition due to harsh environmental conditions it had been exposed to. The object had to be consolidated due to flaking paint and cleaned of surface dirt and support corrosion products. Finally, the object had to be physically strengthened due to the weakness of the support. This process required conservators to combine methods from several different fields of the conservation discipline. Methods employed in the conservation process came less from the literature, due to the lack thereof, and more from the everyday experience of the department and vernacular working practices. The overall methodology of the process has been reconstructed and critically evaluated in the broader field of conservation ethics and the discipline as a whole.     

Conserving a boundary: The conservation and management of a Berlin Wall mural

In 1991, five segments of the Berlin Wall, first painted by renowned contemporary artists Thierry Noir and Kiddy Citny, were bought at auction, transported to the USA, and placed in an outdoor environment that severely advanced the deterioration of the painted surface and reinforced concrete substrate. This paper discusses aspects of the conservation treatment and management plan for these painted segments of the Berlin Wall. The strategy and criteria for the conservation program were defined by a multidisciplinary team that comprised conservators, concrete specialists, and engineers; the deliberations of this team also led to an appropriate treatment and management plan. The choice to intervene at a minimal level meant treatment was restricted to stabilization rather than restoration or reconstruction of deteriorated areas. Additionally, the team decided to reinstall the pieces indoors to reduce future deterioration.     

The conservation and restoration of a processional image: The Christ of the Expiration

Abstract

This image is the work of the sixteenth-century sculptor Marcos Cabrera and belongs to the Brotherhood of the Expiration in Seville. It was made to be carried in procession during the Holy Week celebrations. When the statue came to the ICRBC in Madrid for treatment it presented serious problems due to the unusual material of which it is made — polychromed paper-pulp — and the unfortunate treatments to which it has been subjected. Metal strengthening rods had been inserted in the figure and the cross, as well as a polyester consolidating material which had caused further damage. The polychromy was covered with a thick layer of paint which had plasticized. A complete scientific analysis was carried out by an interdisciplinary team both before and during the treatment which had the aim of stabilizing the sculpture to enable it to fulfil its ritual function.     

Radiography of paintings: Limitations of transmission radiography and exploration of emission radiography using phosphor imaging plates

Radiography in transmission mode is a well-established technique to visualize the internal structure of paintings. However, for many paintings the pictorial layer cannot be clearly visualized with conventional radiography because of interference from paint on the reverse, the material composition or the regular structure of supports or subsurface layers. Traditional lead white grounds in particular cause specific imaging problems not encountered with more modern white pigments such as zinc and titanium whites. A solution to this problem is radiography in emission mode. This study demonstrates and articulates those factors that can interfere with visualization of a painting's pictorial layer using transmission radiography as well as those that contribute to the effectiveness of emission radiography in visualizing such information. While emission radiography has been applied to the examination of paintings for over half a century, it is a cumbersome technique that is further complicated by the need to work under dim safelight illumination when X-radiographic film is used. Therefore, the use of computed radiography using storage phosphor imaging plates for emission radiography was also investigated.     

New insights on the corrosion of ancient bronzes using X-ray powder diffraction: The importance of paratacamite,sampleite, and connellite

Research employing X-ray powder diffraction shows that clinoatacamite as the phase which should be predominant in the chloride-induced corrosion of ancient bronzes is not necessarily the dominant copper trihydroxychloride species at all, since mixtures are common, and other phases such as paratacamite or the dubious mineral phase anarakite have relevance to the corrosion products or patina of bronze antiquities. The potential reasons for this are discussed and related to the compositional parameters of ancient bronzes as well as the burial environment. Paratacamite is still identified, even in the absence of zinc, which is supposed to be the major stabilizing influence on the paratacamite lattice. X-ray power diffraction has been employed in the examination of a range of ancient bronzes from Chinese, Egyptian, Ecuadorian, Lydian, Albanian, Palestinian, and Greek contexts. This study has revealed that, far from being exotic novelties, the occurrence of both sampleite and connellite as important corrosion products of ancient bronzes has been underestimated in the published literature. Many occurrences of sampleite are related to the decomposition of contiguous human remains rather than to arid environmental factors which is the explanation for the occurrence in a geological environment, but in a burial environment other factors come into consideration.