Evaluation of Activated Carbon as a Susceptor in Microwave Dewaxing of Ceramic Shell Moulds in Artistic Casting

Abstract This study investigates the feasibility of activated carbon as a thermal susceptor for microwave dewaxing of ceramic shell moulds with sculptural geometries. Combining microwaves with solid susceptors facilitates the conversion of electromagnetic energy into controlled, localised heat, offering a more efficient and sustainable alternative to conventional methods, which are characterised by high energy consumption, emissions and wax loss. A susceptor stucco containing 15% activated carbon and 85% colloidal silica was formulated and applied to 30 sculptural test specimens, which were irradiated at 1100 W for 70 s. The methodology combined microstructural and dielectric characterisation with thermal testing to evaluate wax evacuation and mould integrity at different levels of residual moisture. Temperatures were measured using a thermal imaging camera, considered the most representative parameter for surface heating. The results confirm that activated carbon is an efficient susceptor, achieving wax removal rates above 90% without combustion and significantly reducing hotspots and cracking. Moderate residual moisture (0.8%) tended to improve the thermal stability of the mould, whereas lower values (0.6%) increased crack formation. Process efficiency depended not only on the maximum temperature reached but also on the uniformity and gradual development of heating, which are critical factors for preserving structural integrity. This work represents a novel contribution to the use of activated carbon in microwave dewaxing, providing an alternative to traditional susceptor materials. The strategy is reproducible and consolidates activated carbon as a key material for cleaner, more efficient and safer processes, with clear potential for implementation under real production conditions.