Photogrammetric Tools for Restoration Purposes: Open-Air Bronze Surfaces of Sculptures

The restoration of an outdoor bronze artefact, among the various processes, provides the cleaning activity, a delicate task that requires a work of synthesis to define - checking step by step its peculiar irreversible process - an effective operating protocol on a limited patch area to be extended to the entire artwork's surface. The paper presents a user-friendly, semi-automated 3D photogrammetry-based solution, developed and validated during the ongoing restoration of the Neptune Fountain in Bologna, able to support restorers in the open-air bronze artwork cleaning from corrosion and weathering decay. The purpose of the developed solution has been to offer an operative and useful support tool for restorers, throughout the restoration work, to ascertain the 'surfaces' to be cleaned, for testing and gathering information (as direct feedback) of the reached results. The proposed solution, in fact, thanks to a customized interface and using an OpenGL viewer, can reproduce with a high level of fidelity in colour and shape the bronze surface before, during and after the clear-out treatment.