Cast Acrylic Sheet

Otto Röhm had worked on acrylic chemistry since his 1901 doctorate. His firm first used polymethacrylate as the sticky middle layer of laminated safety glass - and noticed that the polymer came away from the glass plates cleanly, leaving a clear sheet as smooth as the glass. Sold from 1933 as Plexiglas, the sheet went into aircraft canopies within the decade. **US 2,154,639**, "Process for the manufacture of polymerization products", Röhm and Bauer, assigned to Röhm & Haas, filed 4. December 1935, granted 18. April 1939: methacrylic esters polymerised between sheets of glass and then separated from them, for "glass substitutes" whose faces are "as highly polished as the surfaces of the glass itself". **You use that polish**: an edge-lit sign whose engraving glows while the smooth faces stay dark, and two heat-bent offcuts that show how tight a bend the light survives.