Beyond raw-material substitution: Chemical balancing for resilient porcelain stoneware formulation

The disruption of Ukrainian ball-clay supplies exposed the vulnerability of porcelain stoneware production to raw-material shortages and compositional variability. This study assessed whole-body chemical balancing as a formulation strategy to preserve firing performance when conventional clay sources become unavailable. Eight commercial alternative clays were screened in terms of particle-size distribution, plasticity and thermal behaviour, together with chemical and mineralogical compositions obtained from commercial technical data sheets. Three technologically plausible substitutes were first introduced by direct replacement of the Ukrainian clay package at fixed batch proportions. Despite their suitable individual properties, the resulting bodies showed markedly different bulk compositions and vitrification responses: two formulations met the porcelain stoneware water-absorption requirement only at 1240 °C, whereas one remained incompletely densified within the investigated firing range. Bulk chemical composition was then used as a first-order proxy for predicting firing behaviour and redesigning the formulations by jointly adjusting clay, feldspathic and quartz-rich components while preserving the 40:60 plastic-to-non-plastic ratio. The chemically rebalanced non-Ukrainian body shifted towards a more favourable SiO x – alumosity region and achieved effective gresification at 1200 °C, with water absorption of 0.08% and bulk density of 2.411 g cm −3 . Hot-stage microscopy confirmed rapid densification and a significant stability interval during the isothermal dwell. These results demonstrate that direct mass-for-mass substitution does not ensure equivalent firing behaviour, whereas whole-body chemical balancing provides a transferable route to prospectively design bodies within targeted compositional and technological domains, reduce empirical reformulation and strengthen raw-material supply resilience.