Biologically derived gels for the cleaning of historical and artistic metal heritage

In the general global rise of attention and research to seek greener attitudes, the field of cultural heritage (CH) makes no exception. In the last decades, an increasing number of sustainable and biologically based solutions have been proposed for the protection and care of artworks. Additionally, the safety of the target artwork and the operator must be kept as core goals. Within this scenario, new products and treatments should be explored and implemented in the common conservation praxes. Therefore, this review addressing metal heritage is aimed to report biologically derived gel formulations already proposed for this specific area as reliable tools for cleaning. Promising bio-gel-based protocols, still to be implemented in metal conservation, are also presented to promote their investigation by stakeholders in metal conservation. After an opening overview on the common practices for cleaning metallic surfaces in CH, the focus will be moved onto the potentialities of gel-alternatives and in particular of ones with a biological origin. In more detail, we displayed water-gels (i.e., hydrogels) and solvent-gels (i.e., organogels) together with particular attention to bio-solvents. The discussion is closed in light of the state-of-the-art and future perspectives

La problématique du dégraissage des squelettes

Les techniques actuelles de dégraissage des collections ostéologiques ne donnent pas toujours entière satisfaction et de nombreux muséums d’Histoire naturelle rencontrent ce problème de graisse suintant à la surface des os – notamment sur les ossements poreux et gras des mammifères marins – parfois des décennies après la préparation du squelette : les auteurs rendent compte d’une étude consistant à trouver une alternative aux solvants chimiques toxiques pour le dégraissage du squelette de baleine du muséum d’Histoire naturelle de Nantes

La conservation des os gras : recherche d’un traitement de dégraissage des squelettes de baleine

Les techniques de dégraissage des collections ostéologiques ne donnent pas toujours entière satisfaction. De nombreux muséums d’histoire naturelle sont confrontés à la problématique des squelettes gras. C’est le cas du rorqual commun exposé au Muséum de Nantes. La présence de graisses dans l’os et à sa surface posent un problème d’esthétique (coloration brune), mais surtout de conservation de l’os : la graisse favorise le développement de micro-organismes et son évolution chimique peut altérer l’os. Un traitement de dégraissage est donc nécessaire. Les graisses à extraire sont dans un premier temps identifiées par Chromatographie sur Couche Mince et Chromatographie en Phase Gazeuse. Plusieurs traitements de dégraissage sont ensuite explorés : la voie enzymatique, les solvants et le CO2 supercritique. Le choix du protocole de traitement dépend de son efficacité et de l’impact de la solution de dégraissage sur les composants de l’os. Ces travaux sont donc associés à l’étude de l’altération de l’os après traitement, par spectroscopie FT-Raman.The degreasing methods used for osteological collections are not always completely satisfactory. Many natural history museums are confronted with the problem of fatty skeletons. It is the case of the fin whale of the Nantes Natural History Museum. Fatty bones are unaesthetic (brown colouring), but it is especially a problem of bone conservation: fat allows the development of micro-organisms and a chemical evolution may deteriorate the bone. A degreasing treatment is necessary. Fats to be extracted are initially identified by Thin Layer Chromatography and Gas Chromatography. Several treatments of degreasing are then explored: enzymatic way, solvents and supercritical CO2. The choice of the protocol of treatment depends on its effectiveness and on the impact of the degreasing solution on the components of the bone. This work is thus associated with the study of the deterioration of the bone after treatment, by FT-Raman spectroscopy. The control of the effectiveness of degreasing will be lead by Gas Chromatography

Improving oxygen reduction reaction activity and durability of 1.5nm Pt by addition of ruthenium oxide nanosheets

The durability of commercial carbon supported Pt nanoparticles with an average particle size of 1.5 nm (20 mass% Pt/C) has been improved by the addition of ruthenium oxide nanosheets (RuO2ns) without sacrificing the initial activity towards oxygen reduction reaction. The initial oxygen reduction reaction activity of the composite catalyst was slightly higher than as-received Pt/C. The electrocatalytic activity after consecutive potential cycling tests of the composite catalyst was c.a. 1.3 times higher than non-modified Pt/C. The increased durability of the composite catalyst is attributed to the improved preservation of the electrochemically active Pt surface area with the addition of ruthenium oxide. Keywords: Polymer electrolyte fuel cell, Oxygen reduction reaction, Durability, Ruthenium oxide, Nanosheet

The Effects of Mary Rose Conservation Treatment on Iron Oxidation Processes and Microbial Communities Contributing to Acid Production in Marine Archaeological Timbers

The Tudor warship the Mary Rose has reached an important transition point in her conservation. The 19 year long process of spraying with polyethylene glycol (PEG) has been completed (April 29th 2013) and the hull is air drying under tightly controlled conditions. Acidophilic bacteria capable of oxidising iron and sulfur have been previously identified and enriched from unpreserved timbers of the Mary Rose, demonstrating that biological pathways of iron and sulfur oxidization existed potentially in this wood, before preservation with PEG. This study was designed to establish if the recycled PEG spray system was a reservoir of microorganisms capable of iron and sulfur oxidization during preservation of the Mary Rose. Microbial enrichments derived from PEG impregnated biofilm collected from underneath the Mary Rose hull, were examined to better understand the processes of cycling of iron. X-ray absorption spectroscopy was utilised to demonstrate the biological contribution to production of sulfuric acid in the wood. Using molecular microbiological techniques to examine these enrichment cultures, PEG was found to mediate a shift in the microbial community from a co-culture of Stenotrophomonas and Brevunidimonas sp, to a co-culture of Stenotrophomonas and the iron oxidising Alicyclobacillus sp. Evidence is presented that PEG is not an inert substance in relation to the redox cycling of iron. This is the first demonstration that solutions of PEG used in the conservation of the Mary Rose are promoting the oxidation of ferrous iron in acidic solutions, in which spontaneous abiotic oxidation does not occur in water. Critically, these results suggest PEG mediated redox cycling of iron between valence states in solutions of 75% PEG 200 and 50% PEG 2000 (v/v) at pH 3.0, with serious implications for the future use of PEG as a conservation material of iron rich wooden archaeological artefacts

PROCRAFT Final Meeting WP1 Organisation by Elodie Guilminot

<p>PROCRAFT Final Meeting WP1 Organisation by Elodie Guilminot</p&gt