The wharf-borer Nacerdes melanura L., a threat to stored archaeological timbers

Abstract

A survey of stored waterlogged archaeological timbers from the Mary Rose revealed that 2% of these timbers were infested by larvae of the wharf-borer beetle, Nacerdes melanura L. Timber species attacked included oak, poplar and pine, with moisture contents ranging between 130 and 670%. In addition, scanning electron microscope studies demonstrated that wood tunnelled by the larvae was microbially decayed. The larvae and their life-cycle were studied and emerging adults were observed penetrating the 500 gauge polyethylene used to wrap timbers. Studies showed that 60 Nylon/100I Surlyn, 70 Nylon/125I Surlyn, T 1–19v, T 1–25x and Camvac were more suitable wrapping materials.     

Insect-Infested Wood Remediation by Microwave Heating and Its Effects on Wood Dehydration: A Case Study of Hylotrupes bajulus Larva

Wood artefacts are subject to damage by biologic infestations due to bacteria, insects, and fungal species. One of the worst feared attacks is due to the xylophagous insects whose larvae feed on wood by boring galleries, at the expense of building timbers and worked woods. These beetles are responsible for daily destruction of the world’s wooden cultural heritage, and their elimination has been always a big problem for conservation of wood. The need to avoid the use of chemical methods in conservation for pest control has led to the development of various non-chemical, non-toxic treatments. Among these, heating with microwaves (MW) seems to be one of the most promising, since it has already shown its high efficacy in destroying pests. Insect-infested wood remediation by MW heating in conservation is based on the larger thermal increment induced in larvae than in wood, due to their different dielectric permittivity in the GHz frequency range. However, the side effects that may occur due to MW heating of wood, such as dehydration, have never been discussed so far. Here we study the possible application of microwave heating as a remediation method for wood samples infested by the larvae of the insect Hylotrupes bajulus. We show that it is possible to set up exposure conditions able to achieve 100% of larvae death and that are sufficiently mild not to induce significant dehydration of the exposed wood from which shrinkage effects may derive. Indeed, under these conditions, MW-induced wood dehydration on cubic and parallelepiped sweetgum samples can be kept under control and to percentages as low as 0.4% (w/w).     

An investigation of the use of cellulose-based materials to gap-fill wooden objects†

The conservation of wooden objects is complicated by their response to changes in their environment. In particular, filling voids in wooden objects can be difficult when their dimensions might be expected to alter over time. A short survey of conservators showed that a wide variety of materials have been, and are being used for this purpose. Following conservation work undertaken on a wooden coffin, the author wished to investigate the properties of cellulosic materials and their suitability in the conservation of wooden objects. This paper shares the results of experiments that were conducted to determine the way in which hydroxypropyl cellulose (HPC) and paper pulp fills respond in various conditions, as compared to other fill materials used by conservators. The compatibility of the HPC and paper pulp fills with wood is satisfactory enough to be able to recommend their use in the conservation of wooden artefacts, but ideally further experiments would be carried out, and on a wider variety of fill materials.     

Changing research trends in the field of archaeological wood at the Conservation Department,Faculty of Archaeology,Cairo University

Abstract

Since 1980, much research in the field of treatment and conservation of archaeological wood has been carried out at the Conservation Department, Faculty of Archaeology, Cairo University. Materials and methods used in conservation have been changing gradually over the years worldwide. It was necessary to study critically previous masters and doctoral dissertations on Egyptian archaeological and historic wood, all written in Arabic. This review of them includes a brief history of the Conservation Department at Cairo University and five main focal points of past research: types of wood used throughout Egyptian history, assessment of wood decay, 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.     

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.     

A Note on a Simple Device for Measuring Wooden Artefact Volume

Abstract

The study deals with the development of an air displacement volume-measuring device for the estimation of the volume and calculation of the density of fragile wooden archaeological artefacts. Using a heat-sealed plastic bag as sample holder, an air pump, a flow meter, a pressure gauge and a timer, a number of steps are completed to measure the time required to fill up the bag with air of pre-set pressure with and without the archaeological object. The volume of the subject is then calculated using the empty and loaded bag filling time difference and the standardized air flow rate. The advantages of the device include its acceptable accuracy and low cost.     

Colorimetric Evaluation of Pictorial Coatings in Conservation of Plasterworks from the Islamic Tradition

ABSTRACT

The main aim of our current investigation is the colorimetric evaluation of protective treatments (consolidants) applied to traditional Islamic plasterworks, under natural ageing conditions. From analyses of the original pictorial plaster remains in the Courtyard of the Maidens of the Real Alcázar in Seville, Spain (a World Heritage Site) we prepared test specimens, using materials and techniques similar to the original ones. We analysed 56 test specimens painted with four pigments (yellow, green, blue, and red), using two different binders (animal glue and gum arabic), onto which five representative consolidants were applied: barium hydroxide, acrylic copolymer, polyvinyl butyral, ethyl silicate, and bacterial carbonatogenesis. The test specimens were subjected to natural ageing for one year (indoors and outdoors), enabling a colorimetric assessment to be made of the changes of the polychrome surfaces. The colorimetric heterogeneity of the 56 specimens after ageing registered an average value of 2.7 CIELAB units, assessed using the mean colour difference with respect to the mean. In the aged specimens, the addition of consolidants resulted in average colour differences (mainly lightness differences) of 10.7 and 6.7 CIELAB units, considering as a reference the specimens without consolidants aged indoors and outdoors, respectively. These colour differences were very similar for both binders but not for the four pigments, higher values being found for the blue and red pigments. Considering as reference the samples without consolidants aged outdoors, we found no statistically significant colour differences, either among the five consolidants (p?=?.094) nor the two binders (p?=?.674) used. In addition to the magnitude of colour differences, the choice of the most appropriate consolidants must also consider aspects related to performance and effectiveness. Overall, for the type of paints tested, the polyvinyl butyral consolidant appeared to perform the best, followed by the ethyl silicate.     

CONSOLIDATION OF FRAGILE OBJECTS

Abstract

The condition before treatment and the subsequent consolidation of the wooden parts of an eighteenth century English fire engine are described. Experiments on a range of possible consolidants are outlined, and the application of polyvinyl butyral (Butvar B90, Monsanto) by both brushing and vacuum methods is presented. A closing discussion examines the relationship of the experimental findings to the practical application, the need for consolidation, and the final results of the treatment.     

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.     

THE POTENTIAL OF THE CANADIAN WINTER CLIMATE FOR THE FREEZE-DRYING OF DEGRADED WATERLOGGED WOOD

Abstract

The winter climatic conditions of much of Canada provide an ideal environment for freeze-drying. We have been attempting to use these conditions for the drying of large waterlogged timbers. In the freeze-drying process the wood is kept in a frozen state and the drying proceeds by sublimation. We are particularly concerned with the treatment of large timber which present great difficulties when treated by the accepted methods. A structure was built to keep snow and rain off the wood but which allowed air to pass over it. The structure was covered with polyethylene sheet to allow the sun to shine on the wood surface and heat it. Weight changes in the wood were measured with a load transducer and temperature wa followed with thermocouple probes. Temperature and relative humidity of the surrounding air were recorded instrumentally. The timbers were of several varieties of wood in various states of decomposition. All of the wood dried quickly and much of the water was removed. This technique appears to have the potential to treat large quantities of timber in an economic and simple way.     

Conservation of chemically degraded waterlogged wood with sugars

The effectiveness of two non-reducing sugars, both analogues of sucrose, to conserve degraded waterlogged wood was examined. The two sugars examined are trehalose and sucralose, both stable and relatively unreactive. The ability of these sugars to conserve a series of degraded tongue depressors was measured by determining the anti-shrink efficiency of each at various concentrations and comparing them to sucrose. The findings of this study indicate that both sucralose and trehalose may be effective conservation treatments for waterlogged archaeological wood and that at moderate concentrations the performance of both is comparable to sucrose. However, sucralose has a lower solubility, and concentrations higher than 60% w/v were not examined, whereas concentrations of up to 100% w/v of trehalose were studied. At these higher concentrations trehalose performed as well, if not better than sucrose, although there were crystalline deposits on the wood surface at these higher concentrations. With modifications and careful control, both of these sugars may be suitable conservation alternatives to sucrose due to their long-term stability and resistance to hydrolysis.     

CONSER VATION OF THE WOODEN ELEMENTS IN THE RENAISSANCE HOUSES OF THE PEOPLE’S REPUBLIC OF BULGARIA

Abstract

Furunori (aged paste) is a conservation material that is used for Japanese painting conservation. Furunori is a smoother and weaker adhesive than fresh paste, and it enables the surfaces to be easily peeled apart, with application of water, in a future conservation. Due to these characteristics, furunori has traditionally been used for attaching the backing paper to paintings in Japan, because it is considered that furunori causes less stress on the paintings than fresh paste. This study aims to clarify the characteristics of furunori based on chemical analysis and examination of the microorganisms involved in the early stage of furunori generation. Based on the results obtained, a polysaccharide similar to furunori was prepared.     

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.     

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.     

THE ACETONE/ROSIN METHOD FOR CONSERVATION OF WATERLOGGED WOOD

Abstract

The problem of conservation of sound waterlogged oak and in particular the limitations of polyethylene glycol impregnation are briefly considered. Development of a new process involving dehydration with acetone and impregnation with rosin is described. Results pertaining to the experimental evaluation of the procedure are presented and suggest good success in its use. Applications of the process in the conservation of soft- and heavily waterlogged woods are described.     

Mechanical strength studies on degraded waterlogged wood treated with sugars

This study aims to measure the mechanical strength of chemically degraded wood samples and compare the values obtained with fresh wood and degraded wood treated with sugars. The mechanical strength of chemically degraded waterlogged wood samples was determined using a three-point bending system to generate load-deflection curves and subsequently calculate the modulus of elasticity and load to failure longitudinally. The values obtained allow us to compare the mechanical properties of white birch wood samples that were air dried after treatment with 60% w/v solutions of sucrose, trehalose, or sucralose. In addition, the same parameters were measured for fresh white birch wood samples and chemically degraded samples that were allowed to air dry without treatment. Fresh white birch was found to have a longitudinal modulus of elasticity of 11.5?GPa whereas this value decreased by 70% when the wood was degraded. Treatment with sugars increased the measured values of modulus of elasticity up to 36.9?GPa, a substantially higher value than for fresh wood. These data indicate that non-reducing sugars could be useful alternatives to polyethylene glycol for the conservation of waterlogged archaeological wood.     

Preserving the Open Form. The Oskar and Zofia Hansen House in Szumin: Between architecture and contemporary art

A wooden summer house in Szumin, built between 1969 and 1970, is a spatial manifesto for the Open Form — a theory formulated by Polish architect, artist, and educator Oskar Hansen (1922–05). Oriented towards participation, process, and change in the hierarchy between the architect and the user, or the artist and the spectator, Hansen's theory formed a strong conceptual basis for his architectural, artistic, and pedagogical practice. Being a faithful expression of these ideas, the house is a spatio-temporal, transitional object, defined by constant adaptation to the changing needs of its users. In 2014 the property came into the custody of the Museum of Modern Art in Warsaw, Poland. A conservation strategy was developed to preserve both the idea and the physical aspect of the site. With its dominance of concept and artist's intent, this house has a stronger resemblance with a work of art than with built heritage. Therefore, the procedures developed for the conservation of contemporary artworks have been applied. These tools help to evaluate the range of necessary interventions and to set up a conservation programme.     

Cellulose degradation in the Vasa: The role of acids and rust

Abstract

The oak timbers of the Swedish warship Vasa are deteriorating. High amounts of oxalic acid have been found along with a low pH and low molecular weight cellulose deep in the wood timbers. The iron-rich surface wood differs from the interior wood in that it displays higher pH and cellulose with higher molecular weight. The objective of this study was to determine why there is a difference in cellulose degradation, pH, and oxalic acid amount between the surface region and the interior of the Vasa timbers. Analysis of cellulose weight average molecular weight by size exclusion chromatography was performed, as well as quantification of oxalic acid and iron by high-performance anion exchange chromatography and atomic emission spectroscopy, respectively. It was found that a decrease in iron content coincides with an increase in oxalic acid concentration and a drop in pH at a certain depth from the wood surface. When iron-rich surface wood samples from the Vasa were mixed with an aqueous solution of oxalic acid, a fast increase of pH over time was observed. Neither interior wood poor in iron nor the fresh oak reference showed the same neutralizing effect during the time of measurement. This indicates that the presence of iron (rust) causes a neutralization of the wood, through the formation of iron(III) oxalato complexes, thus protecting the wood from oxalic acid hydrolysis. This effect was not observed to the same extent for other acids observed in Vasa wood (sulfuric, formic, glycolic, and acetic acids).     

Metal corrosion rates in aqueous treatments for waterlogged wood-metal composites

Abstract

Corrosion rates are presented for metals in the aqueous solutions intended for treating both the wood and the metal components of a waterlogged wood-metal composite object. The metals include lead, mild steel, cast iron and the copper alloys of bronze, cast brass and wrought brass. The corrosion rates were determined using a standard weight-loss method in which clean metal surfaces were immersed in the solutions for two months at room temperature. The treatment solutions included Acrysol® G-11O for lead, Witcamine® RAD 1100 for copper alloys and Pluracol® 824 or the corrosion inhibitor Hostacor® KS 1 in PEG 400 for iron. These treatment solutions were prepared in distilled water as well as in a synthetic seawater. For reference, metal corrosion rates were also determined in distilled water, synthetic seawater and PEG 400. The results demonstrate that, in general, clean metal surfaces corrode more slowly in the treatment solutions than in PEG 400 solutions. However, before recommending these solutions for the treatment of composite objects, further testing is needed to determine how effective they are in reducing the corrosion rates of metals covered with a thick corrosion crust, and to see if Acrysol G-110 is capable of bulking and consolidating waterlogged wood.     

Climatological analysis in relation to the conservation of a sixteenth-century spanish polychrome wooden ceiling

Abstract

A sixteenth-century Spanish wooden ceiling was installed in the Morning Room of Hearst Castle in the early 1920s. Since that time, the adhesion between the ground/paint layer and its wooden support has weakened considerably. As a first step in designing an effective conservation program, it was necessary to assess the role of the environment in this deterioration process. Air movement patterns, humidity and temperature parameters, air pollutants, and the impact of approximately one million visitors per year on the microclimate were studied over a one-year period. Correlations between the various components of the study were mapped, including CO₂ concentrations vis-à-vis the number of visitors, and humidity and temperature changes in relation to tourists, air circulation patterns and variations in the external climate. As a result of this study, temporary measures were taken to improve the conditions of the immediate environment and proposals were made for more permanent solutions.