Best selection of adhesive for restoration of archaeological glasses through the modal analysis of its acoustic and vibrational response

The success of conservation related to archaeological glass depends on several factors, including the techniques used and the types of adhesives applied during the reconstruction process. This paper investigates the characteristics of glass conservation by using glass produced with techniques developed by ancient Romans and analysing the modal response of the vibrating surface under airborne and vibrational perspectives. In particular, the conservation process of archaeological glass has been explored, encompassing steps such as cleaning, debris removal. Adhesive usually employed in glass conservation have been tested in many ways (accelerate ageing, cohesion power, etc.) but they were never tested for their vibrational behaviour. Acoustic and vibrational measurements were carried out to scientifically evaluate the performance of two types of adhesives selected from a range of products available on the market. The measurements were conducted under three specific scenarios: (1) on intact glass before any intervention, (2) after a fracture repaired using Araldite® resin 2020 Huntsman, and (3) after a fracture using epoxy resin (Hxtal Nyl-1) B. The results were processed using the transfer function and the cross-correlation of vibrational and airborne values, focusing on the intensity of acoustic radiation (IAR). The findings indicate that the first adhesive B outperforms adhesive A, as the values of the resonance peaks related to the restored glass are closer to the peaks related to the glass measured before the rupture. The tests were performed on a perfect replica of a roman glass made with experimental archaeology.