Co₂K₄O₁₂Si₄

Architectural potential

A cobalt-blue alkali-silicate glass fired at 1150 °C, carrying the family's 500 MPa of compression and a clean transparent body without functional flags beyond colour and structure. The architectural reach is the full load-bearing translucent register: pressed-glass stair treads, transparent partitions in hospital and laboratory interiors, blue glazing mullions for bathing and liturgical architecture, and monolithic light-admitting piers in public interiors where the colour is the design idea. Against float glass the CO₂ sits two per cent lower and the energy sixty-two per cent lower, so the trade-off is favourable on the fire but modest on the carbon; the real argument is that a blue structural element removes a separate glazing layer from an assembly that would otherwise combine steel and tinted sheet. Natural placements are glazed floor panels in entry atria, pressed-glass balustrade units in gallery stairs, and blue column-like piers in meditation and memorial interiors. The batch size at 5 kg workshop ceiling makes staircase-scale runs feasible. The caveat is cost: at €23.38 per 400 g batch the cobalt precursor drives the price high, and the colour is not forgiving of mismatched batches — a pier run needs its cobalt traced to a single supplier lot.

Material character

The slab reads a deep saturated cobalt-blue, the absorption edge near 3.22 eV letting the body carry clear transmission within the blue band rather than a muddy tint. Held to daylight the 47 mm depth deepens the view toward indigo at the long edge and cornflower across the short face. At 2.93 g/cm³ in an 85×85×47 mm format the piece takes a two-handed lift, slightly lighter in hand than the iron-amber sibling of the same dimensions. Cold-cut edges carry the lapidary bloom; the pressed top face sits under a low crown with faint anneal striae. A measurably purer colour than the manganese purple-brown cousin.