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).
The results are reported of a systematic programme of electrical resistance measurement (ERM) of copper and silver corrosion rates within various museum environments, directed towards developing preventive conservation understanding and practice. Electrical resistivity measurements were made using copper and silver probes for one month and one year in 33 locations, and these are interpreted in comparison with two standards. Advantages and drawbacks of different methods available for the evaluation of the corrosion aggressiveness of indoor air are discussed. Practical solutions are proposed for improving the protection of metal objects collections. Improvements are also proposed to maximize the efficiency and suitability of the measuring device to the very specific applications of cultural heritage collections.
Since the 1990s, the Norwegian management for cultural heritage has increased its focus on finding effective solutions for protecting Norway?s wooden cultural heritage from fire damage. The medieval churches in general, including the wooden stave churches, with their interiors and inventories, are of special interest. However, the usefulness of protecting valuable interiors and inventories when fighting fire has been questioned. An experiment was carried out to find manageable solutions for protecting large inventories by using fire covers in case of fire. An experiment using seven commercially available products was conducted by fire fighters to investigate whether these products could protect historic interiors from water and fire. The preliminary results show that it is possible to find manageable, large format covers for the protection of large, immovable historic inventories.
The atmospheric environment inside and outside historical organs in several European regions is reported. In each region, comparisons were made between an instrument suffering organ pipe corrosion and an organ without reported corrosion problems. Concentrations of acetic acid (ethanoic acid), formic acid (methanoic acid), acetaldehyde (ethanal), formaldehyde (methanal) and other volatile organic compounds in the organ environment were determined using active sampling. Temperature and relative humidity were recorded. In addition, polished metal samples that mimic the material used in the historical organ pipes have been exposed in the organ wind systemsfor up to 22 months. High concentrations of acetic acid andformic acid vapours are present in the wind system of the corroded organs. Acetaldehyde and formaldehyde are also present in smaller amounts. The main source of acetic acid is the wood from which the wind system is built. In contrast, formic acid is generated in the church environment outside the wind system. The results show that the two organic acids play an important role in the atmospheric corrosion of organ pipes. It is suggested that the corrosion of lead pipes in historical organs can be effectively reduced by removing the sources of gaseous acetic acid and formic acid in the wind system and in the church environment.
A system for continuous monitoring of atmospheric corrosivity has been developed. An electronic unit measures and records changes in the electrical resistance of a thin metal track applied on an insulating substrate. If the metal corrodes, the effective cross sectional area of the track decreases and the electrical resistance increases. Sensors made of silver, copper, iron/steel, zinc, lead, tin, aluminium, bronze, and brass at thicknesses from 50 nm to 250 μm were tailored for environments with different corrosivities. The developed technology proved capable of providing high sensitivity, allowing for real-time corrosion monitoring even in low-corrosive indoor cultural heritage facilities. Laboratory tests showed good reproducibility with the standard deviation of parallel measurements at less than ±20% for metals which corrode uniformly in the tested environments. Several examples selected from a broad testing programme in partner museums, libraries, and other institutions show successful applications of the logger system for characterization of air quality control in indoor locations, during transport and in temporary exhibitions; assessment of new buildings and storage facilities; and fundamental studies of optimal conservation and storage procedures. A first outline of a classification system for lead, which is particularly sensitive to the presence of carboxylic acids, is given. The technique has a large potential as an independent method for monitoring air quality in facilities displaying and storing valuable objects of cultural heritage.
To guide conservators in their decisions in active conservation of polystyrene materials, seven adhesives were tested before and after light ageing. The material was investigated by assessment of working properties, appearance, colour measurement, tensile testing, hardness measurement, assessment of break type, scanning electron microscope imaging, and assessment of reversibility. Based on a survey among conservators, the adhesives included were acrylates (Paraloid® B-72 in acetone: ethanol, or only ethanol, Paraloid® B-67 in isopropanol, Primal® AC 35, Acrifix® 116), epoxies (HXTAL®-NYL-1, Araldite ® 2020) and one cyanoacrylate (Loctite® Super Attack Precision). Adhesives were tested on extruded sheets of transparent, general purpose polystyrene applied on joined edges and as an open layer. Damage to the plastic could be seen for Acrifix® 116 and Loctite® Super Attack Precision. The average break force sensitivity values indicate that the cyanoacrylate was weakened while Acrifix® 116 was strengthened after ageing. In general, the cyanoacrylate was the strongest and Paraloid® B-67 the weakest. Most adhesives showed yellowing after ageing apart from Acrifix® 116 and HXTAL®-NYL-1. The Paraloids, Primal® AC 35, and the epoxies were possible to remove from the plastic.