Investigation into the Nature and Degradation of Leather and Leather-related Materials within a Museum-based Context

The importance of preventing the degradation of museum objects is undeniable and it is connected with the knowledge available on the item to be stored. Animal skin, leather and synthetic leather are part of museum collections. Their degradation mechanisms have been studied, but that of newly developed coated leather and fabrics are less understood. Likewise, composite materials made of leather fibres and textiles have been commercialised but their degradation mechanism is mostly unknown. Therefore innovative coated substrates, leather, textiles and composites, require thorough investigations because both their identification and degradation can become a problem for museums in the near future. Initial characterisation of natural, artificial and composite leather material with and without flame retardant was conducted using invasive and non-invasive techniques. It was found that successful identification can be carried out with non-invasive methods when both top and reverse side of the materials are accessible. In particular, visual investigation, stereo-microscopy and ATR-FTIR allowed the discrimination of the substrates. However, only the latter was able to discriminate between composites with or without flame retardant. Invasive SEM-EDX and KES-FB2 and KES-FB3 also allowed substrate identification but only EDX discriminated between the different composite materials. Accelerated ageing was then conducted on leather and related materials. Leather-based substrates were characterised by similar degradation pathways, but only natural leather samples showed obvious signs of deterioration in appearance and mechanical properties. The composite’s mechanical properties worsened in the case of substrates containing flame retardant, in particular after high heat and humidity ageing. The appearance of these materials was also partially compromised as demonstrated by the roughness results. The composite without flame retardant and synthetic leather were more stable. Synthetic leather was mainly degraded after severe heat ageing. A list of invasive and non-invasive degradation markers was prepared and the correlation between the roughness and the bending rigidity and work for compression evaluated. In addition, the data collected during the accelerated ageing procedures were examined in the light of the current preventive conservation guidelines for museums and a revised proposal for preliminary guidelines was prepared. Finally, the Proactive Collaborative Conservation (ProCoCo) was developed as a novel approach that has the potential to create a bridge between the knowledge of manufacturers, that of conservators and conservation scientists.