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The reuse of soda-lime-silica scrap or waste glasses as additives for traditional ceramics has been investigated extensively in the literature. Although interesting, this solution does not generally allow large quantities of glass to be recycled. This study reports a novel high glass recycle approach that replaces, in the formulation of porcelain stoneware, the feldspar flux with finely powdered glass derived from the melting of different waste products, e.g. lime from fume abatement systems, feldspar mining residues, and scrap soda-lime glass. At an optimized glass/clay ratio, the ''glass-ceramic stoneware'' samples sinter at 10001C. The ''glass-ceramic stoneware'' has a bending strength approaching 90 MPa and a fracture toughness exceeding 2.0 MPa . m 0.5 , similar to those of conventional porcelain stoneware, which requires sintering at higher temperatures. The high strength and fracture toughness are attributed to the interaction between the glass and clay residues upon sintering, which allows the development of several different crystalline phases.C. Jantzen-contributing editor

Fired microstructures of standard porcelain stoneware tile and tile made from mixes containing waste glass as part of the flux system were studied by XRD, SEM, and TEM. The standard porcelain stoneware microstructure consists of 100–1000 μm long mullite needles, feldspar relics, and partially dissolved α‐quartz embedded in a glassy matrix. The use of soda–lime–silica (SLS) glass in the flux system led to crystallization of plagioclase, wollastonite, and sodium silicates. CaO‐rich areas adjacent to quartz particles, as a result of interactions between SLS glass and silica from the quartz, and eutectic morphologies, revealed that SLS glass accelerated liquid formation and thus sintering and densification. Formation of these additional phases led to lower levels of quartz, mullite, and Na‐feldspar in the microstructure although lower firing temperatures could be used to achieve full density due to generation of more fluid liquid. Use of PbO‐containing waste glasses had little effect on the microstructure compared with standard composition while use of mixed PbO‐containing and SLS glasses led to microstructures containing plagioclase but to lower extent than in tile with higher levels of SLS.