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• An approach for the conservation of waterlogged wood veneered in ivory is described. • Dual evaluation performed on samples prepared in laboratory and on one original piece. • Laboratory samples were artificially degraded putting them in contact with brown rot. • Drying conditions were highly important for the success of the entire treatment process. • Approach applicable where suitable conservation methodology needs to be set-up. This work describes how a conservation method making use of aqueous solutions of lactitol and trehalose (9:1) was chosen to treat several elements of wood furniture veneered in ivory carved in bas-relief and preserved in waterlogged condition. These elements were discovered during the excavations carried out in Villa dei Papiri, the most famous of the luxury villas of Herculaneum. The approach described was based on a dual evaluation. It was carried out: (a) on probe wood specimens produced in the laboratory capable of simulating both the impregnability by consolidants and the deformation of decayed waterlogged wood; (b) on one archaeological element belonging to the original furniture, representative of the material to be treated. The probe specimens produced in the laboratory were artificially degraded by placing them in contact with the brown rot fungus Coniophora puteana , in order to obtain a material of variable decay, similar to that of the original archaeological furniture elements. Three experimental factors were considered when treating probe specimens: (a) the type of substrate, (b) the initial and final consolidant concentration and (c) the drying regime. Three types of substrates were considered: specimens covered with a polycarbonate sheet to simulate the ivory veneer and wrapped in gauze; specimens only wrapped in gauze; and naked specimens, that is, with no obstacles for consolidant penetration. Considering consolidant concentration, the probe specimens were impregnated by full immersion, increasing the concentration of lactitol/trehalose in four combinations: from 15 to 50%, 15 to 60%, 30 to 50%, and 30 to 60%. Last, three drying regimes were considered: 50 °C in an oven, 30 °C/35% RH and 20 °C/65% RH. Results showed that probe specimens whose impregnation started with 30% consolidant in the solution and finished in 60%, and dried under 30 °C and 35% RH exhibited limited volume variations after drying equivalent to those obtained by drying at 50 °C. Drying conditions were important factors in the success of the entire treatment process. As was consolidant uptake, in relation to the extent of decay of the archaeological material. Moreover, the presence of the physical barriers simulating the existence of the ivory veneers and gauzes did not disturb the efficacy of the treatment, as long as sufficient time was given to allow the water-consolidant exchange process to be completed. In the end, the treatment conditions selected on the basis of these probing tests, that is, start with initial concentration of 30%, final concentration of 60%, and drying at 30 °C/35% RH, showed to be successful for treating the representative element of the archaeological furniture. [ABSTRACT FROM AUTHOR]

The viscoelastic properties of wood samples treated with various consolidants [polyethylene glycols (PEGs), lactitol and trehalose, Kauramin, polydimethylsiloxane (PDMS) and trimethoxymethylsilane (MTMS), rosin and polyethylene-L-tartaramide] were evaluated by means of dynamic mechanical analysis (DMA) in order to clarify their effects with regard to the conservation of wood objects. Two softwoods, medium-decayed silver fir (Abies alba) and highly decayed maritime pine (Pinus pinaster), and two differently decayed oak hardwoods (Quercus spp.) were used. In addition, the selected parameters [retention, volume variations and equilibrium moisture content (EMC)] were evaluated to assess the consolidation efficacy. The results showed that in treated wood, both the storage modulus and tanδ depend upon the level of degradation. The impact of the consolidating product was greater in more degraded wood (a higher product amount inside the artefact) compared to well-preserved material, where also wood played a role (also when the products were applied at high concentrations). The values of the different viscoelastic parameters also depend upon the ability of the products to interact with the wood matrix; this characteristic is fundamental to the nature of each consolidant. Lactitol-treated samples showed the highest stiffness increases, whereas those treated with selected PEG combinations and rosin displayed noticeable tanδ increases (high dissipative behaviour). [ABSTRACT FROM AUTHOR]

The analyses to determine the state of preservation of waterlogged archaeological wood follow three different directions: anatomical analyses, physical evaluation and chemical characterisation. Physical parameters (densities and moisture content) are the ones most frequently found in the specialised literature. The measurement of moisture content is normally referred as maximum water content (MWC) in the case of archaeological wood in waterlogged conditions, because wood has been long-time preserved by the lack of oxygen in waterlogged conditions. Aim of the paper is the comparison of three pre-measurement treatments in the calculations of MWC: without any vacuum-pressure treatment, after 300 mbar vacuum pressure and after 50 mbar impregnation in water. The evaluations were performed on 240 samples of waterlogged archaeological wood coming from different excavation sites and including different wood species (both hardwoods and softwoods) in different state of preservation, from low to very high decay. The three tested methodologies to measure the maximum water content on waterlogged archaeological wood provided substantially equivalent results. Nevertheless, a deeper analysis of the results showed that the MWC values of 300 mbar impregnations were rather low compared to MWC standard measurements. Thus, this impregnation was a little bit harsher, causing most probably an anatomical damage on a portion of most degraded samples. The opposite result was obtained after the 50 mbar impregnation procedure. In this case, the MWC values were slightly higher. This means that this treatment seemed to be more effective in subtracting even the smallest air bubbles trapped inside waterlogged archaeological wood samples. Some suggestions on how to measure MWC on waterlogged archaeological wood are detailed at the end of conclusions. [ABSTRACT FROM AUTHOR]

Abstract: Artefacts made of wood coming from archaeological excavations provide insights into human cultural behaviour of the past. They show how man utilised natural resources and how the development of woodworking techniques and artistic endeavour were developed. Within archaeological contexts, waterlogged anaerobic conditions generally preserve the appearance of artefacts, although wood is subject to severe decay processes. The said conditions can transform the original material into a new one, thus demonstrating specific differences from those of the “fresh” wood of the same species. In order to assess these new properties correctly, an integrated diagnostic approach is needed, one which includes a multidisciplinary (micromorphological, physical and chemical) evaluation of the state of preservation. This paper reports several diagnostic results regarding wood artefacts coming from a series of archaeological excavations carried out in Italy. Different types of artefacts – ships, furniture, foundation piles, etc. – that date to different eras (Roman times, the Middle Ages, the Renaissance) have been included in this study. In addition, several species of wood at different levels of decay were analysed. Our study provides evidence of how a multidisciplinary approach, based on anatomical (micromorphological), physical and chemical analyses, avoids goes beyond the limits of each single type of analysis, thus contributing to a complete and reliable evaluation of the state of preservation of these archaeological artefacts. [Copyright &y& Elsevier]

Multidisciplinary diagnostic methods were applied to evaluate the preservation state of waterlogged archaeological wood (WAW) from ancient Chinese shipwreck Nanhai No.1. The characterisation combines micromorphological, physical, and Fourier transform infrared (FTIR) analyses to overcome limitations of using a single analysis. The micromorphological analysis used the whole-slide imaging (WSI) method to identify wood species and determine the decay class. The collected samples were graded as Class 2 (moderate decay) or Class 3 (severe decay). Bacterial and fungal attacks on wood tissues were evident, and the decay pattern of erosion bacteria (EB) was verified. The maximum water content obtained from the oven-drying and freeze-drying methods confirmed that the micromorphological features can be used to grade the decay class. In tandem with hierarchical cluster analysis, FTIR measurements classified four clusters, including moderate and severe decay groups. FTIR also revealed that the chemical alteration of WAW was mainly due to the depletion of polysaccharides. Increased knowledge of WAW degradation and feasible diagnostic methods are beneficial for further conservation strategies. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the work is to set up a methodological approach to verify the effectiveness of the treatments of decayed waterlogged archaeological wood and to point out the proper thermo-hygrometric conditions for its preservation after treatment. The treatments were performed on wood samples of maritime pine (Pinus pinaster Aiton), oak (Quercus sp. caducifolia), elm (Ulmus cf. minor) and strawberry tree (Arbutus unedo L.), obtained from stems pertaining to the original vegetation found in the excavation site of the Ancient Ships in Pisa (Italy), and dated from seventh century BC to second century AD The utilised products were: Polyethylene Glycols (PEG) of various molecular weights, a Polypropylene Glycol (PPG 425), Trehalose (α-D-glucopyranosyl-α-D-glucopyranoside), and their mixtures, and also a Hydroxypropylcellulose (Klucel). The main objective to be pursued by the treatments was considered the stabilisation of the original size and shape of samples. The various steps of this approach were: the execution of a preliminary diagnostic survey on untreated samples; the characterisation of treatment solutions ‘as such’ to establish the property to be monitored during the treatment; the evaluation of the main physical characteristics of wood after the treatment were determined. Among the latter, the coefficient of dimensional stability during the exposure to a series of selected thermo-hygrometric conditions and the retention of consolidants after the treatment. These two measurements allowed the definition of the ‘efficacy of a treatment’, φ T , a new parameter firstly utilised in this work. It measures the stabilisation capability of the percent unit of retained product, and its value permits to put in evidence the consolidants that stabilise wood with the lowest amount of product. Conversely, it was not possible to measure the Anti-Shrink Efficiency (ASE), one of the most utilised parameters for the evaluation of treatments, because of the serious distortions and fractures observed in all the heavily degraded untreated samples. [Copyright &y& Elsevier]

Archaeological excavations in the docking site of Pisa (Central Italy) unearthed several shipwrecks which dated back to the Roman time, from the Republican to the Imperial periods. The recent identification of the woods used for building ships D, E, H, I and P, in addition to data of the previous analysis of ships A, B, C, F, L, revealed the utilization of 18 different taxa . Wood from oaks, both deciduous and evergreen, is mostly represented. 6 different softwood timbers, mostly from maritime and umbrella pine, were also largely used. Some of the hulls were entirely realized with hardwoods, others with softwoods or using a combination of softwoods for planking (mostly pines) and different hardwoods for the frame. The selection of timber indicates a skilful knowledge of the technological properties of the different woods and their suitable utilization in the Roman vessels. The use of woods largely available in the territory surrounding the Pisa docking site, as demonstrated by pollen analysis, does not necessary indicate the local production and/or provenance of the ships, given the spread of the identified wood taxa throughout the North Mediterranean area. [ABSTRACT FROM AUTHOR]