The organic residues of lining in transport vessels from the Red Sea coast of Eritrea: a further element to understand past commercial relations

AbstractThe archaeological site of Adulis lays on the Red Sea Coast of Eritrea and during Late antiquity played a significant role in interregional commerce among the Mediterranean, the Red Sea and the Indian Ocean coasts. Contacts with the Eastern Mediterranean, Arabian Peninsula and the Sasanian world have been attested from different classes of pottery that were brought to light from on-going excavations at the site. Transport vessels have attracted particular attention as they testify the extent of trades and exchange networks. Transport vessels were coated by organic materials to seal porosity and make them suitable to transport different liquids and/or food. The characterisation of coating materials helped shedding light on their function, and support the attribution to different classes of transport vessels found in the Indian Ocean and Red Sea worlds. Here, the characterisation of the organic lining detected on a set of samples identified as Late Roman Amphora 1 is discussed. Results from the chemical analyses, performed preliminarily by FT-IR and then by GC–MS, revealed that bitumen was used for lining the jars, thus leading to set the classification of the amphorae within the wide class of the so- called Torpedo jars. By overcoming the question of typological complexity posed from macroscopic examination of the sherds, the chemical investigation contributed here crucial information for the interpretation of past trading in the Indian Ocean. The research gave clues to broaden the distribution of the Torpedo jars to Adulis, giving an unexpected insight into the trading routes of the past

Nice bronzes in ugly pots. On the containers of the Bronze Age metal deposits from Karmin in SW Poland

Vessels containing deposits of metal items only exceptionally are subject to detailed studies. Only laconic remarks on the presence of pottery sherds or information that metal items were stored in a vessel or vessels are most often published. It seems that metal artefacts are perceived more valuable and thus deserving more attention, while pottery – most often the aesthetically unappealing kitchenware – is considered too plain to be interesting. The paper discusses technological and chemical properties of ceramic vessels from Bronze Age hoards from Karmin, Milicz district, in SW Poland

Navigating conservation strategies: linking material research on alum-treated wood from the Oseberg collection to conservation decisions

From the mid-1800s to the late 1950s, conservation by alum salts (aluminum potassium sulfate dodecahydrate)—with some variations—was a routine method for treating highly deteriorated waterlogged archaeological wood in many countries, especially in Scandinavia. It was eventually replaced by newer methods in the 1960s, such as that using polyethylene glycol. Accordingly, the signs of deterioration in such collections and the reasons behind them are not well known among current preservation specialists. The research in the Saving Oseberg project (2014–2019) has shed light on the consequences of this treatment and reasons behind the severe deterioration observed today in many objects of the Oseberg Viking Age wooden finds, which were conserved in the early 1900s. Saving Oseberg aims to provide research-based recommendations for the future preservation of the finds, and as such, a large part of the project is aimed at improving our understanding of this complex material. Here the consequences of the method are summarized, drawing on the research to date. Chemical analyses of the Oseberg wood showed its current condition to be highly degraded: little polysaccharide content is left and the lignin is significantly oxidized and extensively depolymerized. The conservation implications are also discussed

Ammonium alum in alum-treated wooden artefacts: discovery, origins and consequences

Alum-treatment was extensively applied to archaeological wood from the Oseberg collection in the early 1900s, and was a common conservation method at the time involving impregnating objects with hot concentrated solutions of potassium alum (KAl(SO4)2⋅12H2O). This now obsolete consolidation method has led to dramatic long-term consequences, heavily affecting the state of preservation of the historical wooden artefacts, and dedicated chemical characterisation campaigns have been undertaken to better understand the degradation processes and aid development of re-treatment strategies. Analyses with Fourier transform infrared spectroscopy (FTIR), elemental microanalysis, and ion chromatography (IC) was performed, suggesting the presence of ammonium alum (NH4Al(SO4)2·12H2O) in many alum-treated wood samples, though no record exists of use of ammonium compounds during treatment of the artefacts. C/N rations of 1.70–68.8 in wood samples, and ammonium alum contents between 8 and 84% of the alum component and 23–168 mmol/100 g of total sample suggested that objects were actually treated with various mixes of potassium and ammonium alum. The two alums have similar properties, and in model studies of their behaviour under the conditions of alum-treatment appeared to form similarly acidic solutions, thus the different alum mixtures probably did not significantly influence object treatment. Nor have we observed other indications of unusual degradation pathways related specifically to the presence of ammonium alum. Nonetheless, investigations into potential re-treatment of the archaeological objects must be adjusted accordingly

Comparative chemical investigations of alum treated archaeological wood from various museum collections

From the mid-1800s to the late 1960s, conservation by alum salts (KAl(SO4)2·12H2O—potassium aluminium sulphate), using various recipes, was a common method to prevent shrinkage and to strengthen waterlogged archaeological wooden objects. This method was mainly used in Scandinavia. The alum method appears to have also been applied to highly degraded archaeological waterlogged wood in other countries, for example in the U.S and Germany. Today, many of the archaeological wooden objects treated with alum show extreme deterioration and very low pH, which are attributed to the effects of the alum-treatment. This study investigated the extent of the current levels of chemical degradation in wooden objects conserved with alum salts at different points in time (1880s, 1930s and 1905–13) in order to understand their current condition and whether extent of degradation was in any way related to time of treatment, in an attempt to understand the rate of degradation. It was also an opportunity to compare the chemical state of preservation of alum-treated wood from different collections, as only the Oseberg collection has been intensively studied in this way up until now. Samples from historical wooden objects from the following collections were investigated and compared: the Dejbjerg collection (National Museum of Denmark in Copenhagen); the Oseberg collection (Museum of Cultural History, Oslo, Norway); the Glimmingehus collection (Swedish History Museum, Sweden). Analyses of lignocellulosic polymers and of inorganic compounds were undertaken to evaluate the chemical preservation of the wooden objects. The investigations were performed using a multi-analytical approach which consisted of: pH measurements, analytical pyrolysis (Py-GC/MS), X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDS). It was possible to link the extent of degradation with time, on a general level but we found a great variability in the state of preservation of the wood also within the same collection. It is clear, however that alum-treated wood is more degraded than archaeological wood not treated with alum