A practical comparative study of several treatments for waterlogged wood

Abstract

In this study, the following methods of treatment have been studied: bulking with PEG 4000 in water, methanol and t-butanol solvents; bulking with PEG 540 blend in water; bulking with rosin in acetone; freeze-drying from different concentrations of PEG 400 with various methods of pre-freezing; in situ polymerization with glycol methacrylate and with a melamine formaldehyde resin; water displacement with methylene chloride followed by rosin impregnation. They have all been carried out with five groups of waterlogged wood representative of different species and various states of degradation. Freezedrying, PEG 4000 impregnation in t-butanol and PEG 540 blend impregnation in water gave the most satisfactory results, based on appearance and shrinkage.     

WATERLOGGED WOOD PRESERVATION WITH POLYETHYLENE GLYCOL

Abstract

Polyethylene glycol 1540 was tested in the preservation of a waterlogged, carved, and painted wooden bowl from a prehistoric site on Patarata Island, Veracruz, Mexico. The procedure successfully employed water and Carbowax 1540 in a partial substitution process.     

Cross-sections and Chemical Analysis of Paint Samples

Abstract

Consolidation of decayed wooden artifacts can be achieved by impregnation with epoxy prepolymer dissolved in a mixture of toluene and glycidyl ether and subsequent polymerization in situ. The principles of selecting the successful method of application are discussed, and the details of the procedure given. Impregnation with the described solution causes insignificant expansion of the wood in contrast to the action of polyvinyl acetate in alcohol solution.     

THE CONSERVATION OF TAPESTRIES FOR MUSEUM DISPLAY

Abstract

A broad outline of the considerations which arise with regard to the conservation of a museum collection of tapestries is given in this paper. The various types of damage to, and deterioration of, tapestries is discussed.

Various methods of washing and dry cleaning, and the equipment necessary for these procedures, are reviewed, and a caution is included as to the necessity of testing all dyes for colour fastness in both water and any solvent used for dry cleaning. The equipment, materials and techniques of repair are discussed; three methods of repair being currently used in museums and specialist workshops — re-weaving, stitching on to a backing and the use of synthetic resins for impregnation and adhesion to a woven support. It is suggested in conclusion that the optimum method of repair in museums is stitching on to a backing. More research must be undertaken into the use of synthetic resins, and re-weaving usually alters the original appearance of the tapestry.

Finally, the need for specialised conservation staff in a museum with a tapestry collection is emphasised.     

CONSOLIDATION OF PAINTED WOODEN ARTIFACTS

Abstract

Wood, particularly in the presence of excessive moisture, deteriorates due to action of biological agents and sunlight. Decay manifests itself not only in impairment of physical strength but also in discoloration. Protection of the paint during consolidation by impregnation and polymerization, albeit difficult, is possible. Details of a home-built 23 cm-diameter and 48 cm-long chamber for vacuum impregnation are given. The permeating methylmethacrylate monomer solution used with good results contained bis-4-t-butylcyclohexyl peroxidicarbonate as catalyst, and pyridine as activator in addition to methylmethacrylate polymer, which reduced the rate of heat generation by the reaction. Polymerization induced by gamma irradiation also yielded satisfactory results. Case histories of three artifacts are described.     

Surface spectroscopic studies on patinas of ancient metal objects

Abstract

Surface examination by X-ray photoelectron spectroscopy and Auger electron spectrosopy has beenemployed to investigate the patinas on Lorenzo Ghiberti’s ‘Door of Paradise’from the Florence Baptistry and one of the so-called Riace bronzes. These techniques and the related depth profiling technique are described; the results gave interesting information on thestate of conservation, the original manufacturing process and the possible original appearance.     

The Measurement of Film Thickness and of Solvent Action on Supported Films

Abstract

An efficient and simple method for the vacuum impregnation of stone is described, based on the formation of an airtight jacket around the object allowing a vacuum to be applied to the surface and acting as a wick for the consolidating material.     

Natural polymers as alternative consolidants for the preservation of waterlogged archaeological wood

In recent years, there has been increased interest in examining alternative polymers for the conservation of archaeological artefacts, particularly waterlogged timbers, providing better, renewable, greener alternatives to poly(ethylene glycol) (PEG). The degradation of PEG consolidants in the timbers of the sixteenth century warship Mary Rose has been examined and the rheological and thermal properties of PEG have been compared with its monomethyl and dimethyl ethers and several polysaccharide consolidants (chitosan, guar, and 2-hydroxyethyl cellulose) in order to evaluate their potential as alternative consolidants for the conservation of waterlogged wooden artefacts. Additionally, the effect of the polymers on the archaeological wood was characterised by thermogravimetric analysis and solid-state nuclear magnetic resonance spectroscopy. The results suggest that the future of conservation technologies lies with polysaccharide consolidant materials, which show enhanced compatibility with wooden artefacts with no detectable side effects while also being cheap, with extremely low toxicity, renewable, and sustainably resourced.     

FINDING THE FALLEN: CONSERVATION AND THE FIRST WORLD WAR

Abstract

This study concerns a group of objects excavated in First World War trenches in France and Belgium and brought for conservation to the Institute of Archaeology, University College London. These objects were associated with unidentified human remains thought to be of soldiers killed in battles between 1914 and 1918. The contribution of the Institute to this project was to investigate the objects in relation to their context in an attempt to identify the human remains with which they were associated. The experience of working on sensitive material in a very particular context is discussed, and how this influenced the conservation context in which the decision-making process happened is described. It also addresses how some conservation boundaries were crossed, in order to contribute to a better understanding of life during the First World War, and discusses how material culture is valued differently in different contexts (and how this will influence conservation decisions). It concludes that neither object meaning nor conservation decisions can be viewed objectively and that conservation has to be viewed as a social process governed by economic, political, religious, social and cultural dynamics, rather than a primarily technical process.     

A review of conservation treatments of waterlogged basketry from the northwest coast of North America

Abstract

Basketry artifacts fabricated from spruce and cedar limb wood and root and the inner bark of yellow and western red cedar have been found in water-saturated archaeological sites in the Pacific Northwest since the mid-twentieth century. These artifacts range in age from a few centuries to more than 5000 years old. While these materials retain their overall physical structure due to burial in an anoxic environment they are degraded on the cellular level. Experiments and treatments performed by archaeologists and conservators over the past 50 years have attempted to stabilize these degraded structures and minimize splitting, crumbing, and distortion of the woven structures as they dried. Many of these tests and treatments are published in out-of-print conference proceedings or remain unpublished in conservation lab records. This review of tests and treatments as well as a current condition assessment of several collections brings this information together for the first time and allows conservators and archaeologists specializing in these treatments to see the broader arch of success and failure of the preservation of waterlogged basketry materials.     

Textile conservation in Spain

Abstract

This paper offers a topical overview of textile restoration and conservation in Spain. It discusses the distribution of collections and conditions of research and training. The main textile workshops are described, together with their most important projects, past, present and future.     

A Visit to an ancient Gypsum Quarry in Tuscany

Abstract

Three methods of consolidating stone have been compared using Maastricht limestone as the substrate. They are: impregnation with polymer (Paraloid B 72) from solution; impregnation with a mixture of monomers followed by (a) γ-ray polymerization or (b) free-radical initiated thermal polymerization. The best results were obtained with the third method.     

Technique and treatment of the St Michael Weighing Souls in the Royal Convent of Santa Clara,Toledo, Spain

Abstract

The history, materials and technique of an early fifteenth-century wall painting, St Michael Weighing Souls, are described. The pigments are typical of mediaeval Spain but the methods by which they were applied show a sophisticated understanding of their optical properties. Complex mechanisms of deterioration in some areas of colour are discussed, together with the rationale, materials and methods used in the conservation treatment.     

The conservation of wall paintings in Quito,Ecuador: two case studies

Abstract

Two projects undertaken as part of a Unesco project for the conservation of the cultural heritage of Ecuador are described. Wall paintings in the dome of the church of EI Sagrario in Quito had been damaged by watersoluble salts carried by penetrating rainwater. The dome was protected with a hydrophobic coating and allowed to dry out prior to treatment of the paintings. As part of a programme to train Ecuadorean specialists, paintings on the south wall of a cloister in the convent of San Diego were selected as a model of conservation work.     

La Microstéréoradiographie

Abstract

The application of a ‘feature card’ (or optical coincidence) system of information-retrieval to the field of museum conservation and scientific examination is described in detail. The advantages of the system are briefly discussed and its possible extension to the field of museum registration in general is suggested.     

Approach to the conservation of a mexican saddle and anquera

Abstract

This paper deals with the approach to the conservation of a Spanish-style saddle and anquera (rump cover) from Mexico City and Puebla, Mexico, respectively. The objects were originally bought by an English explorer for a journey and are described in his book. The saddle and anquera are made from vegetable-tanned cowhide with punched and embroidered decoration and metal fittings. The condition, of the leather was assessed scientifically. It exhibits a number of conservation problems, notably surface deterioration and detachment of several sections due to acid attack. Previous conservation treatments have caused the leather to become overstuffed with dressing, resulting in a weakening of the substrate. The conservation ofthe saddle will involve four main stages: removal of excess dressing, stabilization of the leather, consolidation of the friable surface and repair of torn and broken areas. The suitability of various stabilizing agents, consolidants and methods of application was evaluated using mechanical tests alone and accelerated aging and mechanical tests. Naturall y aged and degraded leather was used as an experimental substrate. The results were used to formulate the approach to the conservation of the saddle and anquera.     

Chuc Nichim,the washing of the flowers — a look at traditional preservation practices

Abstract

The ceremonies ofthe Maya people of Chiapas, Mexico, combine Catholic symbolism and ancient ritual. The clothes belonging to the effigies of saints, as well as other textiles, are taken out of storage, washed, dried and incensed in preparation for the saint's feast day. One such feast, Chuc Nichim, is described in detail, and the conservation implications of the rituals are discussed.     

Data in conservation: the missing link in the process

Abstract

There is a missing link in the strategic introduction of new materials in conservation, which lies between the identification of new processes/materials and their widespread use in conservation treatments. Clinical trials to monitor the results of treatment success provide an effective procedure to evaluate the conservation process. This is now possible due to the increasing power and widespread use in conservation laboratories of computers, which provide an analytical tool for evaluating and examining treatments and procedures. Information, such as object condition, is routinely generated during the conservation of objects. To use this information statistically, it has to be structured to answer specific questions. Medical professionals have already established epidemiological techniques as a means of evaluating patient health and treatment performance. These techniques can be applied to conservation questions to provide statistically valid answers. This is an important tool with which to judge and prioritize strategies in the conservation process.     

CALCIUM CARBONATE WHITES

Abstract

The treatment of flaking pigment on two paintings, one on ceramic and the other on glass, is described; a brief history of painting on glass and ceramics places these works in context. The treatments are discussed in relation to other types of treatment for paintings on similar rigid supports. The longevity of the conservation methods used is discussed, as are the results of re-examination of the objects some years after the completion of the treatments.