How did Rayonnant architects make cathedral walls seem like screens of glass and tracery?

Rayonnant architects transformed cathedral walls into expansive, light-filled screens by shifting their focus from massive stone construction to intricate decorative effects. To achieve this, they employed several key architectural techniques:12

• Structural Thinning: Architects significantly thinned the vertical supporting members, reducing the visual weight of the masonry.12
• Integration of Levels: They combined the triforium gallery and the clerestory into one continuous, large glazed area, which unified the elevation and maximized the surface available for windows.132
• Expansion of Tracery: By enlarging the windows and filling them with complex tracery—the delicate stone bars or ribs that divide window openings—architects created intricate, netlike patterns.142
• Lighter Glass: The use of lighter-colored stained glass replaced the deeply colored glass of earlier periods, which increased the visibility of the tracery silhouettes and allowed more light to flood the interior.2

Through these methods, the walls became largely undifferentiated screens composed of glass, mullions, and tracery, effectively dissolving the traditional sense of solid stone boundaries.12