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2. The horizontal sliding glass window/wall in the 20th century, a long technical and architectural evolution
The relatively recent innovations in glass manufacturing described in the previous chapter are part of a long process of technological and architectural evolution that runs through the entire history of the 20th century.⁶
2.1. The ‘fenêtre en longueur’
The “column-beam-slab” reinforced concrete structure, popularised from the first decades of the century, decomposed the traditional façade wall by replacing it with lightweight, flexible structures. This innovation paved the way for a new transparency between interior and exterior space, consequently leading to a radical change in the
design of the frame and in the concept of the opening itself. Moreover, the period coincides with the industrialisation of glassmaking – boosted by the shop window market, which was demanding ever-larger and more transparent glazed surfaces – finally turning it into a standard, affordable product.
At the beginning of the 20th century, the industrialisation of plate glass⁷ was based mainly on two methods, rolled plate glass and flat drawn sheet glass. The first method consisted of pressing molten glass with rollers until the desired thickness was obtained.⁸ This process easily produced translucent glass but, in order to obtain an acceptable transparent glass, required the faces of the sheets to be ground and polished. The second method, that of flat drawn sheet glass – or the Fourcault process⁹ – consisted in the production of a continuous glass ribbon drawn vertically by lifting it upward through cooled tubular rollers from inside the pit. Despite the good fire-finish, this type of glass had greater limitations in size and inevitably presented a wavy or striped surface. The two methods were perfected in the 1920s, consolidating the path of the Modern Movement. In the case of rolled plate glass, Pilkington developed a system in 1925 that guaranteed continuous feeding and finishing.
The flat drawn sheet glass technique was perfected by the Libbey-Owens and Pittsburgh processes which, from 1925, allowed for larger manufacturing dimensions and greater thermal and thickness homogeneity.¹⁰
Thus, once the dimensional limit imposed by the lintel was overcome and the plate glass technique was perfected, conditions were created so that the glazed surfaces could extend to the whole extent of the façade, like Le Corbusier’s ‘fenêtre en longueur’. The panoramic window with sliding sashes thus became an icon of Modern architecture:
“Plate glass replaces window panes. The sashes run horizontally, unhampered by the clumsy accessories of the sash windows. They make possible the lengthwise window the source of an architectural motive of great significance.”¹¹
The horizontal window, as codified in Les Cinq points d’une architecture nouvelle (conséquence des techniques modernes) (1926-27), was opposed to the traditional porte-fenêtre or fenêtre en hauteur, originating a heated debate with Auguste Perret, from 1923 onwards, on the appropriate form of the modern window and the reorganisation
of the visual field.¹² The main objective was to maximise the entrance of natural light ¹³, but also to open the landscape: ¹⁴ the window became an optical device, a large screen.
By removing the dependency between the openings and the supporting structure, reinforced concrete created the possibility of the façade being entirely constituted by a continuous glass frame: the ‘pan de verre’. This even more complex and radical proposal gave way to glass houses – which embody a different notion of interiority,
maximising the visual relationship with the outside world – and the curtain wall.¹⁵ This formal transfiguration of buildings led to the gradual loss of autonomy of the window, transformed into the skin of the façade. Or else, the façade wall was transformed into a window.¹⁶
Flat drawn sheet glass production (the Fourcault Process). Excerpt from an advertisement for Union des Verreries Mécaniques Belges – Univerbel, La Maison, 1955, vol. 11, n.12. © Union des Verreries Mécaniques Belges
6. For an analysis of the evolution of the curtain wall during the 20th century, we refer to the following texts, to which the present text is indebted: Chapter 3 of Iñaki Abalos, Juan Herreros, Tower and Office: From Modernist Theory to Contemporary Practice, Cambridge MA: MIT Press, 2003 (original version:
Iñaki Abalos, Juan Herreros, Tecnica y Arquitectura en la Ciudad Contemporanea, 1950-1990, Madrid: Nerea, 1992), and from Chapter I of Scott Murray, Contemporary Curtain Wall Architecture, New York: Princeton Architectural Press, 2009.
7. Flat glass process was patented in 1848 by the British engineer Henry Bessemer. For the first time, a continuous ribbon of plate glass was produced, formed between rollers but it was not a commercial success.
8. It could be poured on a metal surface or directly on two rollers. This second technique, the 1920s Bicheroux process, allowed better control.
9. This process was invented in 1906 by the Belgian engineer Émile Fourcault. Independently, Irving Colburn developed a similar technique in the United States of America at around the same time.
10. After the invention and widespread diffusion of the float process and despite its inferior quality, flat drawn sheet glass continued to be used during the post-WWII period until the mid-1960s.
11. Le Corbusier, “Twentiethcentury Building and Twentieth-century Living”, The Studio Year Book on Decorative Art, London, 1930.
12. See in this regard: Le Corbusier, Petite Contribution à l’étude d’une fenêtre moderne, in Almanach d’Architecture Moderne, “Collection de l’Esprit Nouveau”, Paris: Éditions G. Crès, 1925, pp. 94-101; Bruno Reichlin: “The Pros and Cons of Horizontal Windows: The Perret-Le Corbusier Controversy”,
Daidalos 13, 15 September 1984, pp. 65-78; Beatriz Colomina: Privacy and Publicity: Modern Architecture as Mass Media, Cambridge: MIT Press, 1994.
13. “Through the use of the horizontal window reinforced concrete suddenly provides the possibility of maximum illumination.” Le Corbusier/Pierre Jeanneret, Five points towards a new architecture 1926. “L’architecture c’est des planchers éclairés.” Le Corbusier, Précisions sur un état présent de l’architecture et de l’urbanisme, Paris, Éditions G. Crès, 1930, p. 53. For Le Corbusier, natural lighting was a preponderant factor, writing as early as 1920, that “architecture is the masterful, correct and magnificent play of volumes brought together in light.” (“Trois rappels à Mm. les architectes,” in L’Esprit
Nouveau, no. 1, October 1920, p. 92; later included in Vers une Architecture, Paris, G. Crés et C.ie, 1923, p. 16).
14. “Le paysage entre tout entier dans votre chambre.” François De Pierrelefeu, Le Corbusier: La Maison des hommes, Paris, Éditions Plon, 1942, p. 69.
15. Suggested in the proposals for skyscrapers in Berlin by Mies van der Rohe (1919 and 1921) and the cruciform towers of Le Corbusier (1920-22), it was
used by Gropius on the façade of the Bauhaus in Dessau (1926) and since then adopted mainly in office designs.
16. The anti-window character – or the window as “absence of walls” – of the Le Corbusier and Mies projects in the 1920s and ‘30s, serves as a counterpoint
to Venturi’s nostalgic essay on windows. Robert Venturi, “Windows–c. ‘65” in Iconography and Electronics upon a Generic Architecture: A View from the Drafting Room, Cambridge, MIT Press, 1996, pp. 255-258.
