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Systematic methodological monitoring of the performance of old and new sealants for fluid collections
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Edité par CCSD -
International audience. A key element in the proper conservation of specimens in fluids is the closure system for glass jars. These vary widely in both historical and modern collections. While every collection manager can see over the years that not all these solutions are equivalent and by no means infallible, few systematic scientific studies of the performance of old seals have been published. After studying the hermeticity of various sealants for flat glass lids on model jars, we have implemented a systematic methodological follow-up of their ageing when exposed to fluids. We have built up models of seals, deposited on glass slides, considering old sealants recipes (Lataste cement, Glaziers' putty, Bauer mixture) and modern silicon seals of various compositions, which we subjected for 130 days to vapors of (or immersion in) 10% formalin, 75% ethanol and modified Kaiserling III glycerol solution (plus water as control). Monitoring was aimed at characterizing visible changes (swelling, loss of adhesion), as well as accurately measuring changes in color (using spectrophotometric measurements and hardness (Shore A). Possible chemical changes in the composition were also determined using infrared spectroscopy. The methodology developed for was finally adapted to widely used gaskets (natural or synthetic rubber, polymer).In addition to the practical difficulties of implementing this systematic methodology for such different materials, our study shows the importance of the choice of silicones used, particularly in collections preserved in ethanol (more or less rapid loss of adhesion and hardness, swelling, yellowing, partial depolymerization of the seals, acidification of the fluid).
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