Glass compatibility is a crucial factor in glass recycling. While the coefficient of thermal expansion (CTE) is often the primary criterion for assessing compatibility, the interaction between different glass compositions is governed by a broader range of material properties and processing conditions. Differences in miscibility, viscosity, thermal history and thermokinetic behaviour can all influence the quality and integrity of the resulting material.

A better understanding of these interactions could help identify ways to mitigate incompatibilities through processing, expanding opportunities for high-quality glass-to-glass recycling and reducing downcycling.

Glass casting provides a means to systematically investigate these factors on a small scale. This exhibition presents a matrix of kiln-cast glass tiles, each combining a pair of glass compositions with varying degrees of CTE mismatch, ranging from 0 to 4.0. The horizontal axis represents two casting temperatures, 860 °C and 1120 °C, while three cullet sizes are explored: powder (<250 µm), medium-sized fragments (1–10 mm) and stacked flat glass pieces.

Together, the tiles reveal how material combinations and processing conditions influence the resulting glass, illustrating the complexity of compatibility and the potential to move towards a more comprehensive, physically grounded understanding of this property.

This exhibit is part of the UPCAST glass research project. More information on this project can be found here.

Relevant publication: Compatibility Limits of Mixed CTE-Viscosity Glass Melts

Research team: Lara Neuhaus, Telesilla Bristogianni, Faidra Oikonomopoulou

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