Gypsum board in 1950s: Type X · 477

CaSO4·2H2O panels that buy fire time by calcining — the everyday A2/A1 lining of interiors. Gypsum board is one of 32 materials in this atlas, grouped under fire: history, structure, measured properties, process routes, uses, safety and market — not a product catalogue. Scores compare Gypsum board with the rest of the atlas on strength, heat, fire behaviour, insulation, workability and circularity. They are editorial, not certificates.

Seven chapters follow. Fire and insulation claims name test families (Euroclass, ASTM E84, ISO 5660, KS F) rather than inventing a single safety number. Gypsum board (CaSO4·2H2O + paper faces) is a family of grades whose density ~700–1000 kg/m³, heat band calcines ~80–180 °C (dehydration), and fire letter A2-s1,d0 typical; core A1.

Gypsum board is sold as grades, not as a single substance. Chemistry CaSO4·2H2O + paper faces, density ~700–1000 kg/m³, heat band calcines ~80–180 °C (dehydration). This atlas treats Gypsum board as a system: mill route, coatings, tests and the cavity it sits in. Conductivity note: ~0.17 W/m·K. Insulation score 34/100 is relative to 32 entries — metals lose, VIPs and aerogels win.