3D digital technologies applied to the design and printing of auxiliary structures for fragment adhesion strategies on wax artifacts

Abstract

Three-dimensional models of anatomy in wax preserved in university museums are rare artifacts of extraordinary technical complexity. In recent years, interest in them has increased among scholars who consider them primary sources of heritage value to approach material culture and the history of science. The fragility of the sculptural material and the inadequate exhibition and storage conditions of many of these collections have caused the formation of pathologies whose conservation treatment is a great challenge for the restorer. In this regard, new 3D digital technologies have created a great impact on the documentation and analysis of interventions in the field of conservation and restoration of cultural heritage. This research aims to demonstrate the technical possibilities offered by 3D digital systems as support tools in curative conservation strategies to mechanically stabilize fragmented sculptural parts. For this case study, we chose an 18th-century obstetric anatomical model made by the Madrid Court sculptor Juan Cháez, and the modeler Luigi Franceschi who belonged to the anatomical cabinet of the Royal College of Surgery of San Carlos in Madrid. In this work, we demonstrate the digitization process carried out employing structured light scanners, digital modeling, and 3D printing. The aim is to create auxiliary structures suitable to support the various original pieces to be adhered while guaranteeing their exact position during the adhesive curing process as well as the volumetric reintegration of faults. In addition tensile and three point bending tests for the mechanical characterization of the selected thermoplastic impression materials are described. Finally, the qualities considered suitable for the most appropriate material for the purpose of the study are detailed. Promising results were obtained since the structures have made it possible to perform fragment adhesions in highly complex areas of the sculpture, ensuring maximum precision, safety, and efficiency during the process.