K₄O₂₀Si₈V₂

Architectural potential

A potassium-vanadium silicate glass fired at 1150 °C — a load-bearing translucent at five hundred megapascals of compression, with the vanadium tinting the body a cool grey-blue rather than delivering a switching behaviour at this ratio. Placements sit in the walked-on and leaned-on register: stair treads where the cool tint reads against warm timber nosings, balustrade panels and glass screens in public circulation, structural floor inserts in mezzanines and gallery cores, and pressed-glass beams in pavilion frames where the grey-blue colour is part of the spatial register. Against float glass the energy overhead drops by sixty-two per cent because the potassium flux lowers the melt viscosity, while embodied CO₂ is essentially unchanged — a thermal-argument substitution rather than a carbon one. The 400 g standard batch scales cleanly to a five-kilogram workshop ceiling, genuinely usable for a full set of treads or a short balustrade run rather than a single sample. Still firmly in the soda-silicate family, so anneal schedules and cold-edge finishing remain part of the detail. The caveat is colour specification: the grey-blue body is not a near-clear tint, so daylight passing through a tread sits cooler on the treads below, and architectural lighting studies should account for the cast rather than assume float-like neutrality.

Material character

The slab reads a distinct cool grey-blue — more saturated than a tinted architectural float and closer to a pale sapphire than to a neutral grey, the vanadium sitting as a dissolved colourant in the silicate matrix rather than a particulate. At 2.61 g/cm³ over 85×85×53 mm the piece is firm in the hand and lifts two-handed for its thickness, closer in weight-feel to an ordinary soda-lime pane of the same dimensions but slightly denser. Surface pressed-glass with the characteristic convex crown of a cast pane; edges cold-cut, carrying the lapidary bloom of a slow saw. Rings clear and long under a tap.