K₄Mg₂O₂₀Si₈

Architectural potential

A magnesium-doped alkali-silicate glass fired at 1150 °C at workshop batch, carrying 500 MPa of compression and a clean clear body — the family's most neutral load-bearing transparent member. Natural placements are the full load-bearing transparent canon: pressed-glass floor panels walked on from above, stair treads, transparent partitions in laboratories and clean-room interiors, pressed-glass beams and ribs in entry porticos, and monolithic light-admitting columns where daylight through a structural pier is the design idea. The 100×100×40 mm slab format is the largest in this batch, which tracks with the higher workshop ceiling (5 kg) and matches the physical register of a small floor panel or a balustrade module directly. Against float glass the CO₂ is two per cent lower and the energy sixty-two per cent lower, so the carbon argument is slender but the fire argument is strong. The magnesium addition stabilises the melt and produces a cleaner anneal than the pure potassium-silicate baseline. The caveat is the tectonic: like any soda-lime relative, edge conditioning and annealing are not optional — a cracked chamfer or a rushed cool turns a 500 MPa element into a brittle one, and the detailing has to respect that from the first drawing.

Material character

The slab reads a clean clear body without visible tint — the closest member of the atlas to ordinary window glass in colour, though not in thickness. At 2.47 g/cm³ in a 100×100×40 mm format the piece sits solidly on the bench and resists the single-handed lift, distinctly heavier than a float pane of comparable footprint because of the 40 mm depth. Cold-cut edges show the usual lapidary bloom; the pressed top face sits under a low convex crown with two faint anneal striae running the long dimension. Against the iron and cobalt siblings from the same firing the colour argument is absent — clarity, weight, and the 40 mm depth carry the reading.