Phenol Formaldehyde Revisited—Novolac Resins for the Treatment of Degraded Archaeological Wood

Archaeological wood is usually severely degraded. The Norwegian Viking Age Oseberg find exemplifies problems arising due to past conservation treatments and the need for new types of preservatives. Phenol formaldehyde (PF) has been investigated as a consolidant for alum‐treated wood. X‐ray tomography has revealed that it is possible to obtain a porous structure inside the wood, ensuring ethical acceptability by allowing re‐treatment. In order to understand the curing mechanics, the kinetics of the initial condensation reaction were elucidated at room temperature. It was found that a second‐order reaction using both phenol and formaldehyde concentrations is the most probable mechanism.     

出土饱水木质文物的微生物腐蚀及防腐措施

在南方保存完好的出土木质文物大都处于饱水状态.出土后因为水和氧气的参与,在水解作用、微生物腐蚀等诸多因素的作用下,木质文物逐步被降解而变得腐朽.为此,本文从木质文物的微生物腐蚀机理着手,提出控制水活度的办法、控制氧气量、毒化微生物赖以生存的养料三种途径来防止或延缓木质文物的腐朽,以等待将来更好的脱水定型方法出现.     

Preservation,storage and display of waterlogged wood and wrecks in an aquarium: “Project Aquarius”

A test aquarium containing water and waterlogged historical wooden material was observed during a three-year period at Vänernmuseum, Sweden, to test the feasibility of preserving and exhibiting archaeological wood or shipwrecks in a way accessible to the public. Experiments were also set up in a laboratory environment, to provide information on single factors that could influence the long-term preservation state of wood, and other processes that may occur in the water.     

Reasoned use of chemical parameters for the diagnostic evaluation of the state of preservation of waterlogged archaeological wood

Waterlogged archaeological wood undergoes decay processes that depend on both the burial conditions and the constituting species, and which cause the depletion of the structural components of wood cells. To quantitatively assess the state of preservation of the decayed material, specific parameters are usually measured by means of both chemical and physical analyses. In this paper an innovative approach in the use of the data obtained from these kinds of measurements is developed. A series of 132 archaeological wood samples of different wood species, burial times and states of preservation, and coming from different sites in Italy, was analysed. Their residual chemical composition, maximum water content and basic density were measured, and a reasoned use of these parameters was carried out through their elaboration, with the aim of both evaluating eventual incongruence or anomalies in the raw physical and chemical data (which has never been accomplished so far) and directly comparing in a reliable way the analytical results obtained from archaeological samples with very different states of preservation. This approach allowed defining the effective values of chemical parameters related to wood decay according to a same reference basis of calculation among the various data. By this way, it was possible to state that lignin can be also attacked by the agents causing biotic decay, and that in hardwoods its decay is more related to the burial conditions than to the wood species. Instead, the mechanism of polysaccharide depletion is diversified: conifers showed a uniform behaviour whereas hardwoods were more species-dependent. Moreover, in addition to the chemical composition, also anatomical factors influence the carbohydrate rate of decay in waterlogged wood.     

Computed tomography study of snuff trays from San Pedro de Atacama (Northern Chile)

Wooden snuff trays from San Pedro de Atacama (SPA) in northern Chile are objects of particular museological value. Computed tomography (CT), a non-destructive analytical technique useful in the analysis of archaeological objects in which physical tampering is not desirable, was used to study provenience of wood, quality of craftmanship, taphonomic processes and nature of gemstone inlays in a group of snuff trays. While wood used in the manufacture of trays was mostly exogenous to SPA, gemstones used in inlays were likely of local origin. These findings support the active exchange of goods proposed for the south-central Andes region. Several features revealed in the trays support the view that craftsmen producing them were skillful artisans.     

Potash - a key raw material of glass batch for Bohemian glasses from 14th-17th centuries?

The aim of this work is to verify or refute hypothesis of existence of basic/universal glass batch: quartz sand: potash: limestone, at a ratio of 2: 1: 1 used in Bohemian glass production since the middle ages onwards and to simulate the preparation of a potassium glass type with the composition used in medieval Bohemia. The chemical composition of Bohemian glass, which incorporated in the proposed glass batch for glassmaking on a laboratory scale, was evaluated by (a) findings directly related to glassmaking (samples from glasswork in Moldava dating back to the 15th century) and (b) information from publications.Experimentally produced glasses for the present paper were prepared from raw materials such as ash, leached ash, potash, limestone and quartz sand. The plant raw materials (spruce, beech and bracken ashes, raw and refined potash) were treated and prepared by methods similar to the production procedures used in the pre-industrial era.The main contrast was found in the CaO/K₂O weight ratio, which was determined in glasses that were characteristic of given periods. While this ratio was often below 1 in glasses of the 15th century, it reached values above 1 in glasses at the turn of the 16th-17th centuries. This result may indicate that the composition of the glass batch had changed.The results of the present study reject the current scholarly work dealing with glass batch composition during the 14th-17th centuries and confirm that glass produced in some Bohemian medieval glassworks could have been melted from a batch that included plant ash, making the use of limestone unnecessary. The traditional suggestion of the exact ratios of raw materials, often cited in historical literature, seems to be impossible. The glassmakers had to react to the variable composition of the raw materials, especially plant ash.     

Fuel, Fire and Heat: an experimental approach to highlight the potential of studying ash and char remains from archaeological contexts

As in traditional societies today ancient societies probably selected different fuels to meet specific heat requirements. Char and ash, the end products of fire, are often found in abundance in archaeological contexts. These end products can provide information regarding (i) the original fuel resource and type, (ii) the characteristics of the fire and (iii) combined with other archaeological evidence shed further light on possible socio-economic activity(-ies) associated with that fire. The three main fuel resources would have been (i) modern vegetation, (ii) fossil fuel and (iii) animal by-products. Local availability and abundance would have influenced the choice made.In this study an experimental approach was adopted to try and distinguish between the three different fuel resources that are known to have been used by ancient societies (and continue to be used by traditional societies today) from their char and ash remains to help determine original fuel-type and understand the relative heating properties. For this end one fuel-type from each fuel resource listed above, namely wood, peat and cow dung, was chosen.     

Direct Displacement-Based Design of Glulam Timber Frame Buildings

We introduce a direct Displacement-Based Design methodology for glued laminated timber portal frames with moment-resisting doweled joints. We propose practical expressions to estimate ultimate target displacement and equivalent viscous damping, and we demonstrate that these expressions provide prior values that are close to those obtained a posteriori using a more refined model. Applied to case studies, the method yields base-shear forces lower than those obtained using the force-based approach of Eurocode 8. This is due to the high dissipation capacity of the specific connection technology, which apparently is conservatively accounted for in the q-factor of Eurocode 8.     

Fuelwood,crops and acorns from Iritegi cave (Oñati,Basque Country)

Abstract

We present the analyses of plant macroremains from Iritegi, a cave from Northern Iberia with archaeological levels dated from the Chalcolithic to the Iron Age. Wood charcoal assemblages are dominated throughout the sequence by Fraxinus. Other important taxa are Quercus subg. Quercus, followed by Corylus avellana, Fagus sylvatica, Ilex aquifolium, Taxus baccata and Ulmus. Acer, Alnus and Maloideae occur in very low numbers. The high percentages of Fraxinus are possibly result from the selection of ash for fodder. Evidence for the use of crops (Hordeum vulgare, Triticum aestivum/durum) comes only from the Chalcolithic contexts. The identification of acorns in one Chalcolithic hearth shows that roasting of these nuts was taking place maybe to improve taste and to facilitate further processing or to improve storage conditions. The results show that plant food gathering still played a role within the subsistence of farming human groups in the region.     

Preservation potential of charcoal in alkaline environments: an experimental approach and implications for the archaeological record

Charcoalified plant material (usually wood) has been described as being inert with a high preservation potential. Although usually black on both the outside and inside, the physical and chemical properties differ as a function of temperature and time of exposure to a heat source. Post-depositional processes however may exert additional affects on charcoalified material and introduce bias into the archaeological record. This work explores the influence of alkaline conditions, often encountered in the soil environment, on the preservation potential of charcoalified material. Charcoal, experimentally produced at different temperatures, was exposed to a number of solutions of potassium hydroxide and calcium hydroxide with different pHs, to simulate exposure to alkaline soil conditions. Under these conditions chemically mediated physical interactions occur resulting in fragmentation of the charcoal samples into (very) small pieces the size of which depends upon the initial temperature of charcoalification. Moreover further interactions result in a decrease in reflectance relative to samples not exposed to alkaline conditions. Although experimentally driven the potential for physical loss of charcoal from a particular site coupled with the reduction in (expected) reflectance of any resident material, has important implications for any conclusions drawn regarding the archaeological record.