Assessing wood adhesives used in conservation by testing their bond strength and ageing behavior

The aim of this work was to study comparatively the performance of adhesives commonly used in conservation of wooden artefacts of Cultural Heritage. Three natural adhesives, casein, rabbit-skin glue and fish glue, and two synthetic, a copolymer of methyl acrylate and ethyl-methacrylate (Paraloid B72) and a polyvinyl acetate glue (Ravemul M18 - Vinavil), were investigated. Their performance was tested on mock ups made of two different species of wood, Abies alba L. (fir) και Acer pseudoplatanus L. (maple). The adhesives were evaluated for their performance before and after accelerating ageing with UV and RH-T cycles, in relation to bond strength under shear stress. Criteria important in conservation such as reversibility and colour stability were additionally investigated in order to get a more complete picture of adhesives’ performance. The results showed that Paraloid B72 and fish glue demonstrated the highest bond strength. Paraloid B72 and fish glue were also the most reversible, before and after accelerated ageing. In contrast rabbit-skin glue became less reversible after subjected to RH-T cycles. Vinavil and Paraloid B72 were found to be the most colour stable adhesives under UV ageing. The best overall performance was presented by Paraloid B72 and fish glue.