B₂₈Cu₂Er₈

Architectural potential

An erbium-copper boride sintered at 1100 °C, this belongs to the powder-pressed metal hardware register — brackets, connector nodes, façade clips, furniture joints, cast-like fittings that would otherwise be machined from billet or welded from plate. Three hundred and fifty megapascals of compression and a fifty-three-per-cent cut in embodied CO₂ against structural steel put it directly into the conversation with cast-steel node details in glass-and-steel envelopes, timber-frame moment connections, and the small-run custom hardware of workshop-made furniture. Natural placements are connector plates in CLT-to-steel transitions, façade-anchor bases where geometry wants to be curved rather than milled flat, and signature furniture legs or balustrade cleats in exhibition fit-out. The extremely low apparent density (0.76 g/cm³ at a 120×120×92 mm slab dimension suggests high as-sintered porosity) and the 200 g standard batch with a 500 g workshop ceiling mean specification is per-piece, not per-run — closer to a foundry commission than a catalogue order. The caveat is verification: erbium supply is constrained, cost runs €11.42 per 200 g, and medium-confidence compression data means first structural use should be tested to failure on a representative geometry before the detail is committed.

Material character

The slab reads a warm green-red copper surface with the erbium content pushing slight pink undertones into the matte — unusual for a sintered metal, and distinct from the neutral greys that dominate the family. At 0.76 g/cm³ over 120×120×92 mm this is a remarkably light piece for its size, lifting single-handed with the register of a closed-cell foam rather than a metal billet — its sintered grain is coarse and the body is clearly porous. Surface matte with visible sinter-grain texture; edges as-formed from the press die rather than cold-cut. Against a cast-copper sibling it reads chalkier, lighter and more granular in the hand.