Co₄Na₄O₁₄Si₄

Architectural potential

A structural cobalt-blue glass slab — the one-shot combination of load-bearing capacity and saturated historic colour that ordinary cobalt stained glass cannot offer. Five hundred megapascals of compression at 3.282 g/cm³ lifts this above sheet glazing into the pressed-glass element register: coloured glass-floor panels in exhibition architecture, cobalt-blue stair treads in civic interiors, light-wells that cast a deliberately coloured daylight into the space below, pressed-glass beam inserts where both structural and chromatic presence are wanted. Against float glass the CO₂ balance is nearly neutral (-1.9%) but the energy reduction in the melt is sixty-two per cent, and the cobalt content is doing the architectural work that no clear float product can deliver. Natural placements are sacred, memorial, and civic interiors — a space where the Chartres-blue quality of a walked-on floor panel, or the transmitted cobalt wash of an inhabited glass pier, is the defining spatial argument. Workshop batch reaches 5 kg, supply-chain score is 1.0. The caveat is cost: €36.85 per 400 g batch from cobalt oxide precursor shifts the specification away from bulk glazing toward signature placements, and the melt-tank logistics require cobalt-specific ventilation and personal-protection discipline that a clear soda-lime production line does not.

Material character

A deep saturated cobalt-blue body — the old stained-glass register translated into a pressed structural form, darker at the long-edge sighting than at the face view. At 3.282 g/cm³ and 85×85×42 mm the slab reads heavier than clear soda-lime stock of the same geometry, a two-hand lift with the weight of a thick paving slab. The top face carries a shallow pressed-glass crown and faint anneal striae near the long edges, standard soda-lime tectonics. Edges come cold-cut with the usual lapidary kerf bloom; the blue deepens noticeably along the thickness, translating a three-centimetre look into a four-centimetre read when sighted edge-on.