A portion of the windows in the exterior glazed curtain wall of the Prada store was manufactured as a complex curve. To achieve the double curve, flat float glass was slumped against a custom mold (Schittich 2006). To slumped glass, a manufacturer slowly heats a flat glass sheet. The sheet will begin to sag and deform from its own weight. Using a mold for this process precisely controls the curvature of the glass. Reheating the glass to create the curvature also achieved a partial pre-tension on the glass (Shittich 2006) and thus increased its strength compared to annealed glass.