The specialty of objects conservation encompasses a broad range of materials and object types. This issue of Studies in Conservation features papers that focus on objects made of metal, glass, wood, and ceramic materials used for art, archaeological, ethnographic, or decorative arts objects. The papers are related to each other by their common interest in practical conservation impact; they report on treatment studies or on research that is strongly related to treatment decision making. Taken together, they reflect well on the current state of the field, filled with innovation, vitality, and continuing progress.
Continuing progress is very clear in the review paper that opens this issue. Nesrin M. N. El Hadidi reports on changing research trends in the field of archaeological wood at the Conservation Department, Faculty of Archaeology, Cairo University. El Hadidi conducted a critical review of all Cairo University's masters theses and doctoral dissertations on Egyptian archaeological and historic wood. As these were all written in Arabic, this review will be especially enlightening to non-Arabic speakers. A brief history of the Conservation Department helps to set the stage for a discussion of the state of the research conducted there. El Hadidi classifies the past research into some overarching themes: characterization of the types of wood used throughout Egyptian history, assessment of the effects of decay on wood properties and composition, treatment and conservation of decorated wood, and the evaluation of chemicals and polymers used in the treatment of archaeological wood and composite objects containing wood. Evolving priorities and interests are reflected in the varying topics highlighted in the review, and in the changes over time in materials and methods that were of interest to researchers. As many conservators outside of Egypt either work in institutions housing Egyptian collections, or participate in field conservation at archaeological sites in that country, this review should be of great interest.
The first original research or treatment paper in this issue continues with a study of wood. Charlène Pelé and colleagues focus on the problem of iron removal from waterlogged wood, experimenting with extraction by electrophoresis and chemical treatments. In some environments, waterlogged wood may be exposed to iron oxides, which can lead to a degradation of the wood matrix. Experiments were designed to test a number of extraction treatments, and to determine treatment efficiency. Electrophoresis and simple immersion treatments were tested with a wide variety of chemical solutions, and a pre-treatment was developed to improve extraction rate. The results highlight the complexity involved in treating waterlogged wood, with many treatment parameters that can affect results, as well as variations in materials and burial environments that must be considered. Hence research into best practices for treating waterlogged wood continues to be a very active topic in conservation.
Alice Paterakis and Michael Steiger look at a conservation problem typically encountered with ceramic materials, salt efflorescence. They study this problem in the context of pottery housed in the collection of the Athenian Agora, American School of Classical Studies, Greece. They first review results obtained since 1990 in examination and analysis of salt contaminants for the purpose of identification, and of simulation tests to determine source(s) and mode of formation. Means to mitigate the contamination and the crystallization-deliquescence cycles (consolidation, desalination, and climate control) were also studied. Here we find publication of the first solubility and deliquescence diagrams of the Ca(CH3COO)2–CaCl2–H2O system at 25°C, as part of a detailed discussion of the processes involved in the formation of acetate salt compounds. The Athenian Agora staff instituted preventive conservation measures that include desalination as a remedial measure instead of costly replacement of existing wooden cabinets by enameled steel storage cases, as there are already some 52,000 catalogued ceramics in storage. Since 1979, all newly excavated ceramics and all ceramics exhibiting efflorescence in the collection have been routinely desalinated; the past practice of removing calcium carbonate encrustations with hydrochloric acid also ceased at that time. In spite of high concentrations of volatile acetic acid concentrations in wooden storage cases in the collection, no efflorescence has formed on the desalinated objects.
Eva Rydlová and colleagues report on their study of materials and decorative techniques and on the conservation treatment of two early seventeenth century Stangengläser (tall cylindrical glass vessels) from the collection of the Museum of Decorative Arts in Prague. The objects were severely damaged, and with the presence of both diamond-point engraving and cold-painting, were challenging to treat. The initial technical research revealed differences between the two objects in decorative technique, although both had similar potash-lime-silica glass compositions. The technical studies helped to inform treatment decisions, and also contribute to art historical discussions about possible provenance of the Stangengläser (a glassworks at Wilhemberg, South Bohemia). The detailed discussion of the conservation treatment procedures provided here will be of interest to anyone who must treat glass objects, regardless of cultural context.
The paper by Noëlle Timbart and colleagues reporting new data on a bronze statue of a Meroitic archer-king (from northern Sudan) is somewhat unusual for Studies in Conservation. The original round of technical studies, and a full conservation treatment (both on-site at the archaeological excavation and later in the laboratory), were conducted in the 1970s and published in 1986. For a 2010 exhibition in Paris, a new program of analysis was carried out. The new technical studies were able to take advantage of 40 years of advancement in knowledge and analytical techniques. Examination of the object showed that new conservation treatments were required. For example, an adhesive that had been applied 36 years previously had turned brown. Other surface discolorations were linked to consolidation operations carried out in the field; and new problems were observed with integrity of gilding layers and with advancement of corrosion. The re-treatment was informed at every step by the availability of very thorough documentation of the original treatment protocols. This paper demonstrates the importance of monitoring and periodic examination even for those objects that receive thorough treatment at one point in time, and of the need for ready availability of good treatment documentation to aid future re-treatment needs that may emerge.
This themed issue concludes with a technical note by João Cura D'Ars de Figueiredo Junior and colleagues reporting on the characterization of corrosion products on metals excavated from sealers’ occupation in Antarctica in the eighteenth and nineteenth centuries. Archaeological excavations in the Livingston Islands have recovered artifacts of iron, lead, and copper alloys, mostly small objects revealing aspects of the everyday life of seal hunters. The burial environment produced a wide variety of corrosion products; in particular, phosphorus and phosphates could be attributed to the sealers’ activities, and serve as important markers of human presence in this extreme environment. The conservation treatments, which began immediately upon excavation and continued in the laboratory, are also described here.
These six papers represent the healthy state of objects conservation today. There is a good balance of applying current scientific knowledge and techniques with an emphasis on reporting new developments and approaches to practical conservation treatments. Methods of preventive conservation, and understanding the effects of the environment on deterioration, are as important as the development and testing of new treatment methods and materials. There is also recognition of the necessity of reflecting back on past treatment approaches as a way of better planning the way forward. These theoretical ideas and the practices they generate should be of interest to the conservation field in general, beyond the specialty of objects conservation.