The curtain wall begins above the lobby. The curtain wall, above the arcades and lower stories, is composed of non-structural glass walls, which were designed to be heat- and glare-resistant. There are about of glass panels. Because the windows are permanently sealed, and because the tower rises without any setbacks, the Seagram Building's window washing team could not use standard window-washing equipment. Therefore, a custom-made pneumatic scaffold was installed, with a deck that covers six columns of windows at a time. Behind each window, Mies sought to avoid irregularity when window blinds are drawn, since people using different windows would draw blinds to different heights. As a result, the building uses window blinds with slats angled in 45-degree positions, allowing the blinds to be set in three positions: fully open, halfway open, or fully closed. facade used 1,500 tons of bronze, manufactured by General Bronze. The glass panes are set within vertical bronze mullions made from extrusions of I-beams. The bronze mullions are arranged in bays, with five columns of windows in each bay. Unlike at Lever House, where General Bronze had also manufactured mullions, the Seagram Building's mullions were only for aesthetic purposes and was thus susceptible to thermal expansion or contraction. At the building's completion, General Bronze said the facade would need to be cleansed twice a year with soap, water, and lemon oil to prevent discoloration; this work could be performed using the custom window-washing scaffold. The windows on each story are separated horizontally by spandrels made of Muntz metal, which gave the spandrels an appearance similar to that of copper. A sample facade section, tested in a wind tunnel in 1956, was found to be resistant against winds of up to .