K₂O₁₅Si₆V

Architectural potential

A potassium-silicate glass with vanadium colouration, reaching 500 MPa of compression and carrying both the structural and the translucent arguments at once. At 1150 °C it melts and anneals cleanly, and the 400 g batch with a 5 kg workshop ceiling gives enough reach for repeated column and tread runs. Natural placements are load-bearing pressed-glass elements where the vanadium colouration is an architectural asset rather than a defect: grey-blue stair treads in residential interiors, partition beams in gallery spaces, pressed glass piers in bath-house or spa architecture, and floor panels walked on from above in small atrium installations. The visible-absorber chemistry of the vanadium content doubles the piece as a passive solar-gain surface — on south-facing glazing, the slab takes visible light into itself rather than reflecting it, warming up as it filters. Against float glass the embodied CO₂ is essentially neutral, energy two-thirds lower, so the specification carries no environmental penalty. The caveat is annealing — at 51 mm depth the slab must come out of the kiln slowly to avoid internal stress, and edge conditioning is part of the tectonic. Saw-cut or kerf-polished edges are not interchangeable with fire-polished ones.

Material character

The slab carries a deep, even grey-blue from the vanadium-silicate absorption edge, distinct from the cooler cobalt-blues of the ceramic palette — steadier, more mineral, with a graphite undertone along the long sight line. At 2.71 g/cm³ in an 85×85×51 mm piece, the body sits in the familiar heavy-glass register, firm two-handed. Translucent rather than clear: the 51 mm depth reads almost opaque head-on, but a strong light behind the slab passes through with a saturated blue cast. Surface carries pressed-glass sheen with faint anneal striae on one long face; cold-cut edges show the lapidary bloom, edge-polish is optional tectonic.