B₃₆K₁₂S₃₄
sulfide polysulfide · sulfide low tempB36K12S34 is a sulfide polysulfide suitable as sulfide low temp. Color: yellow-orange. Fired at 130°C from 3 precursors (B2O3, S, K2CO3). Workshop batch: 500g at €10.17. Compressive strength ~50 MPa; estimated 0.09 kg CO₂/kg (-89% vs Portland cement). Notable: forms without a kiln. Confidence: high.
- forms at
- 130 °C · hotplate · no kiln
- replaces
- portland cement
- CO₂
- 89.1% lower than Portland cement (0.09 vs 0.83 kg CO₂/kg)
- energy
- 89.1% lower than Portland cement (0.60 vs 5.50 MJ/kg)
- compressive
- 50 MPa
- density
- 1.79 g/cm³
- crystal
- monoclinic
- band gap
- —
- cost
- €20.34/kg · €10.17 / 500 g batch
- confidence
- high (synthesis route)
- potential
- 0.71 · env 1.00 · novel 1.00 · struct 0.10 · lineage 0.70 · supply 0.27
- flags
- zero kiln: Forming happens without firing — the material cures through chemistry at ambient or hotplate temperature. At building scale this removes the kiln from the supply chain: on-site casting, regional workshops, cold-country fabrication all become available.
Architectural potential
This is a high-confidence zero-kiln polysulfide formed at 130 °C on a hotplate, delivering an eighty-nine-per-cent reduction in embodied CO₂ against Portland cement at the modest compression figure of 50 MPa. The compressive strength places the material firmly in the non-structural surface register: interior tile, inlay, signage plate, acoustic-wall overlay, decorative threshold. Natural placements are large-format floor tile in low-traffic gallery and exhibition interiors, amber-yellow wall inlay panels in hospitality fit-outs, and cast sill-plates in retrofit carpentry where kiln access is absent. The 100×100×56 mm slab scales generously by sulfide standards — 500 g batches up to 2 kg workshop capacity — and the warm yellow-orange body gives the material a distinct visual register the cement world cannot supply without pigment. Against Portland cement the argument is the removal of the kiln entirely: ambient cure, chemistry-formed, regional workshop logistics. The caveat is supply and safety together: boron-potassium-sulfide precursor sourcing sits at a supply-chain score of 0.29, and while the safety margin is comparatively clean for the family, any saw-cutting workflow still wants dedicated ventilation. Bulk structural use is ruled out by the compression register, so specification belongs to surface and tile scale.
Material character
The slab reads a saturated yellow-orange body, close to an unfired turmeric pigment, distinct from the copper-red and purple registers of the metal-rich polysulfides. At 1.79 g/cm³ and 100×100×56 mm the piece lifts single-handed with real presence but no strain — firmer than a pine board of the same size, lighter than any fired ceramic. Surface cast mold-matte with the characteristic meniscus sheen of a hotplate pour; edges come as-cast with a fine sulfur bloom crystallising across the face over time, visible under raking light as a pale frost. Lighter and warmer in tone than the Cu-Mn-Na sibling; the boron-potassium matrix keeps the body closer to wax than to mineral.
Recipe
500 g batch · peak 130 °C| element | precursor | formula | mass | safety |
|---|---|---|---|---|
| B | boron oxide (or borax Na2B4O7) | B2O3 | 60.18 g | safe |
| K | potassium carbonate / potash | K2CO3 | 39.82 g | safe |
- Pre-heatHotplate to 150 °C
- MeltSulfur liquefies at 115 °C; full liquid at 130 °C
- CastPour at 140–145 °C
- SetRoom temperature 30 min (firm) → 24 h (full strength)
Zero-kiln process — 130 °C hotplate cast only