Material Continuity in Ceramic Restoration: A Firing-Based Protocol Integrating Digital Technologies — Reconstruction of a Chinese Export Porcelain Tureen Lid (Caramulo Museum, 2019–2023)

This paper documents the development and application of a ceramic restoration protocol based on reintegration using materials identical to the original object — paste and glazes fired at high temperature — in Chinese export porcelain. The protocol addresses the problem of material incoherence between the original object and its reconstruction, ensuring compatibility of thermal behaviour and equivalent durability, which are unachievable with conventional synthetic materials. The case study focuses on the complete reconstruction of the lid of a Chinese export porcelain tureen belonging to the Caramulo Museum. The intervention, carried out between 2019 and 2023, involved the selection and characterisation of compatible ceramic pastes, glaze matching, dimensional modelling compensating for the shrinkage coefficient (16.8%), and the integration of 3D scanning and ceramic 3D printing to resolve complex lid-fitting geometry. Through an interrupted firing protocol at defined temperature thresholds — 150°C, 350°C and 573°C — the alpha→beta quartz transformation was identified as the critical moment of crack formation. The solution involved separating the functions of the firing support and firing the components independently, eliminating the internal stresses responsible for the cracking. The process required 20 iterations over four years, resulting in a porcelain lid delivered to the Caramulo Museum in September 2023. The protocol is not a universal solution: its application is conditioned by the scale of the intervention, the technical feasibility of execution in compatible ceramic systems, and the conditions of firing process control. Reconstructed elements are marked with the author's signature and year of execution, ensuring permanent traceability.