C₂Mo₂Na₆O₁₄Si₂

Architectural potential

A thermal-mass ceramic in the heavy-oxide register, pitched to the passive-solar and radiant-heat-storage role. Five hundred megapascals of compression with a mass density of 3.15 g/cm³ puts it well above brick for thermal-flywheel capacity, but the CO₂ cost is high — over three times that of a clay brick — so the argument cannot be an environmental one. The case has to be functional: a south-facing trombe-wall infill that shifts peak heat release by six to eight hours, a hypocaust-style radiant slab in a gallery or chapel floor, a night-flush cooling core in a double-skin façade, or a heat-storage panel set behind a solar-collector glazing. The sodium-molybdenum-silicate matrix densifies at 1250 °C and gives the slab genuine compressive capacity alongside its thermal behaviour, so the panel is self-carrying rather than frame-supported, which simplifies detailing in retrofit work. Supplement, not replacement: this is not a substitute for insulation; it lives behind or within the insulated envelope and does its work over the diurnal cycle. The caveat is triple: high firing energy, high material cost at €13.93 per 200 g, and untested at wall scale in architectural production. Specification belongs to prototype thermal-wall research and one-off signature elements rather than to repeated trombe infills.

Material character

The fired body reads a neutral warm grey with a faint yellow undertone from the molybdate phase — not the orange-ochre of a clay brick, not the cool grey of concrete, something halfway between terracotta and pumice. At 3.15 g/cm³ and 85×85×44 mm the slab handles with real ceramic heft, a deliberate two-finger grip and a full-kilo weight in the lift. Surface finishes vitrified-matte from the 1250 °C hold, with a fine closed grain visible under raking light and a slight skin-darkening where the molybdate migrated to the face during the hold; edges cold-cut, kerf-whitened along the diamond-saw line. Tapped, it rings cleaner and higher than a clay brick of equal size — a denser, more mineral voice, closer to a stoneware than to a standard-fired brick.