Glass casting offers the potential to create complex, large-scale, monolithic structural elements with optimized stiffness and material use. However, glass's brittleness and lack of post-failure redundancy pose safety challenges, especially since conventional float glass safety strategies are difficult to apply to volumetric components. Inspired by reinforced concrete, this study explores embedding metal reinforcement in cast glass directly during the casting process to enhance ductility, redundancy, and recycl-ability by avoiding adhesives. The novelty lies in directly bonding metal to glass using materials with similar thermal expansion coefficients, further allowing contamination-free recycling. Building on previous TU Delft research, we investigate two material combinations with matching thermal expansion coefficients: (i) bor-osilicate glass with F15 Kovar and (ii) soda-lime silica glass with Titanium Grade 2 or 5. Kiln-cast glass beams with a longitudinal metal reinforcement are produced and tested under four-point bending using Digital Image Correlation to assess their mechanical performance. Borosilicate glass specimens reinforced with Kovar demonstrated effective glass-metal interaction but lower strength due to interfacial bubbles, with all specimens failing in shear, in a similar manner to reinforced concrete, while retaining most glass attached to the metal rod. Soda-lime glass specimens reinforced with Titanium exhibited higher failure loads, though specimens reinforced with Grade 2 Titanium failed in bending similar to unreinforced glass. Titanium Grade 5 reinforcement showed potential for strength enhancement and progressive failure, emphasizing the importance of proper reinforcement selection and dimensioning. Finally, we discuss the potential for mate-rial separation at end-of-life and the applicability of this technology for embedded connections in cast glass.

Located in Apple Park in California (USA), Mirage is an outdoor sculpture of 448 solid cast glass cylindrical columns, each 210cm high and 15cm in diameter, made from 70 different desert. sands. The sculpture by Katie Paterson and Zeller & Moye involved a large team of artists, architects, geologists and scientists. This paper discusses the experimental work conducted by TU Delft on devel-oping glass compositions of the desired colour, hue and tint, as a function of foreign, impure sand addition to the basic batch recipe. XRF and XRD analyses of the desert sand samples revealed their chemical composition and crystallographic structure, purity level and presence of undesired con-taminants. Repetitive melting experiments led to establishing relationships between the sand character-istics and the colour hue, tint and intensity of the resulting glass, concluding to 0.02-17% desert sand content as substitute of the original, low-iron sand in the batch recipe. Iron oxides were identified as the prevailing colour agents, yielding a colour palette of blue, aquamarine and green hues based on their oxidation state. The melting experiments led to the formulation of a glass recipe prediction model and to modifications of the standard batch, towards achieving the desired colour gradient while preventing critical defects in the glass. The vertical casting of the columns by the glass studio gave a distinct surface pattern with recess lines and a high bubble content. To identify if the strength is governed by the surface quality, the bubble content or the glass's chemical composition and to attain representative strength data, 4-point bending tests were conducted on 37.5x51x635mm beam specimens produced by the same foundry. Fractography analysis of the tested specimens showed that the characteristic surface pattern governs the design strength. Mirage was inaugurated in May 2023, showcasing the potential and versatile beauty of using a wide range of impure sands in glass making.

Glass casting displays great forming potential allowing for the realisation of three-dimensional glass elements of virtually any shape and size, as showcased in glass art. Disposable mould technology seems to be ideal for the fabrication of such customised and complex geometries, including for architectural and structural cast glass components deriving from structural topology optimization, since it offers great shape freedom and cost effectiveness. However, currently, glass casting on disposable moulds faces the major drawback of a resulting rough and opaque glass surface quality, requiring considerable post-processing to yield a glossy, smooth surface. This in turn results in a compromised dimensional accuracy and on increased time and production costs. If the surface remains unprocessed, it can greatly affect not only the visual but also the mechanical properties of the cast glass element. Aim of this research is to improve the surface quality of complex glass components cast in disposable moulds, directly during demoulding, reducing in this way the need for post-processing. To achieve this the research focuses on exploring ways to pre-process disposable moulds. In specific, the research focuses on series of kiln-cast laboratory experiments at various maximum firing temperatures / annealing schedules involving the use of two different types of disposable moulds, 3D-printed sand moulds and silica plaster moulds (Crystalcast®), and the application of refractory coatings, coating combinations and protective layers. The experimental work conducted thus far indicates that the best results are obtained at the lowest maximum temperature tested (870 °C), with the combination offering the best finishing quality to be a synthetic (ceramic) sand mould coated with Crystalcast® and Zirkofluid® (6672, 1219). Scaling-up of the kiln-cast prototypes unveils a complex correlation between the maximum dwell time at the maximum firing temperature and the casting effectivity/ performance of mould materials and coatings.

Recent research at TU Delft has highlighted the potential of using structural Topology Optimization (TO) for designing large monolithic cast glass structures of maximized stiffness with minimal mass. The mass efficiency of these structures results in considerably shorter annealing times and, consequently in improved manufacturability in terms of time, energy and cost efficiency. Nonetheless, the geometrical complexity and customization of the resulting forms renders them challenging in terms of fabrication. Exploring the manufacturability of such intricate glass structures, in this paper we discuss the different possible fabrication methods for three-dimensional glass structures of complex and customized geometries, via a review of existing literature, experimental work and prototyping. Specifically, with the aim of addressing all possible manufacturing solutions, we look into the following fabrication methods: (i) casting in disposable moulds; (ii) waterjet cutting and lamination of float glass panes and; (iii) additive manufacturing of glass. We assess these methods based on a set of criteria linked to the structural performance, visual quality, fabrication limitations and sustainability. Accordingly, we discuss the potential, challenges and practical limitations of each fabrication method for real-world applications of TO glass structures. Subsequently, we propose the integration of alternative constraints into the TO formulation, so that customized TO tools that better reflect each fabrication method can be created.