La₄Na₄O₅₆Si₂₄

Architectural potential

A lanthanum-sodium silicate glass tuned for the load-bearing-transparent register: 500 MPa of compression at 85×85×46 mm with clear optical transmission through the thickness. Natural placements are pressed-glass stair treads in public buildings, transparent floor panels in atria where daylight needs to carry between levels, light-admitting piers in gallery vestibules, and monolithic glass beams over reading tables. The lanthanum addition raises the density and refractive index without tipping the body out of the soda-lime family, so annealing, edge-grinding and adhesive-joint detailing stay within conventional pressed-glass practice. Against float glass, embodied CO₂ is effectively flat at two per cent lower, but firing energy drops by sixty-two per cent — the argument for this material sits on the furnace hour rather than on the carbon accountancy. Workshop batches reach five kilograms, so full tread-sized or small panel-sized pieces are within reach; the 1150 °C peak keeps it inside a ceramic-capable kiln but out of ambient fabrication. The caveat is lanthanum itself: rare-earth sourcing sits under continuous supply-chain pressure, the estimated batch cost of €6.80 per 400 g is already above the selenium-silicate sibling, and any large specification needs a procurement strategy rather than a single order.

Material character

The 46 mm slab reads as a clean, slightly cool transparent — a fractionally bluer clarity than the selenium-silicate sibling, tied to lanthanum's shift in the absorption edge. Through the 85 mm face the view sits fully transparent; sighted along the long edge the body picks up a faint cold-water tint. At 3.00 g/cm³ the slab lifts with a firm two-hand grip — heavier than the average soda-lime pressed slab, a distinct step up from the Se-variant at the same footprint. Top face sits under a low convex crown with two faint anneal striae close to one edge. Cold-cut edges carry the familiar lapidary bloom and a clean conchoidal kerf.