K₄O₁₈Si₆V₂

Architectural potential

This is a load-bearing transparent glass with a vanadium-driven grey-blue body — 500 MPa of compression combined with the visible-absorber chemistry that makes the body itself into a selective solar-gain collector. Natural placements are south-facing pressed-glass beams in conservatories and glasshouse architecture, structural stair treads walked on from above where a warm-grey tinted body is acceptable, transparent partitions in thermally active double-skin façades, and light-admitting column piers in atria where the body gently warms under direct sun. Because the glass absorbs rather than reflects visible light, it doubles as a thermal-collection layer in trombe-wall assemblies and in absorber-panel work — the structural piece and the thermal collector become the same element. Against float glass the embodied CO₂ is nearly level at minus two per cent, so the environmental argument is modest; the real gain sits in the sixty-three-per-cent energy reduction during forming, plus the functional thermal-absorber behaviour the body carries. High confidence across the data, supply-chain and safety scores at 1.0 — this is one of the more specifiable materials in the atlas. The caveat is annealing discipline: potassium-silicate-vanadate bodies at 48 mm thickness need patient edge conditioning and a controlled cool, or the load-bearing claim collapses into fracture at the corner.

Material character

The slab reads a saturated cool grey-blue body, dense enough to read as true colour rather than tinted clarity, with light transmission scaled to the 48 mm depth — chartreuse-grey at the top face, deepening along the long edge as the slab thickens. At 2.91 g/cm³ and 85×85×48 mm the piece sits stably on the bench and asks for a two-hand lift. Surface finishes pressed-glass with the faint anneal striae typical of a controlled cool, visible close to one long edge; cold-cut edges carry the lapidary bloom from the diamond saw. Distinct from the clear Na-Sn variant in the family, where the same mass delivers transparency rather than real tint.