Introduction

Glass

A material that is neither liquid nor solid, glass is amorphous, hovering between the two states. In a near-magical process, ordinary sand is transformed into a fragile, see-through material. This transformative nature of glass has captured people’s imagination throughout history. From the 11th to the 16th century, the secrets of glassmaking were highly coveted by the Venetians, until three glassmakers were smuggled in by King Louis XIV of France for Versailles Hall of Mirrors. Glass’s historical exclusivity continues to impact metaphors associated with glass today. Crystals, glass, and minors appear symbolically in literature, art, and architecture, both religious and secular. Art historian Rosemarie Haag Bletter traces the history of glass as a metaphor of transformation in society, from the tales of King Solomon and the Renaissance Dream ofPoliphilo to German Expressionism and Bauhaus.¹ Glass slippers, coffins, and mirrors often appear symbolically in fairy tales, which describe the collective dreams of a culture. In modern architecture, glass is a material imbued with idealism, symbolism, and utopic vision.² Glass’s fragility, which intensifies its exquisiteness, along with difficulties in thermal control, have challenged architects over the past century. As Bletter writes, because of glass’s preciousness in preindustrial periods, coupled with its brittleness, glass appeared frequently in architectural fantasies — in the “realm of wishful thinking.”³ Glass is physically heavy, but metaphysically light. Together, these are the basis of the paradoxical allure of glass.

Glass, in a seemingly multivalent contradiction, combines immaterial qualities with material properties. Following an accelerated development in materials and glass engineering in the past few decades, knowledge about both spatial effects and technical performance of glass has greatly expanded. In this time period,

FIGURE 1.1 A drawing from the book Alpine Architecture by Bruno Taut. Glass architecture built on Monte Generoso gives the effect of glass mosaic.

Akademie der Künste, Berlin, Alpine Architektur aus dem Bruno-Taut-Archiv Nr. 21.

architecture has witnessed an emergence of technical advancements - including chemical coatings that alter reflective and refractive properties, plastic lamination interlayers that give structural stiffness to glass panels, and fabrication techniques that allow precision machined hardware to become embedded in glass. Consequently, structures that could only be drawn or written about previously, including those by prophetic poet Paul Scheerbart and the visionary architect Bruno Taut (Figure 1.1), have now been realized. As material properties are altered, they, in turn, call into question the prevailing social and cultural symbolisms and metaphors associated with glass. It is necessary, therefore, to reconsider glass transparency in the context of recent developments and cultural changes. The prevailing perceptions of glass have become blurred, both materially and metaphysically.

Transparency

Transparency is both fundamental and elusive. In architecture, its metaphorical meanings are as multivalent and mutable as the visual effects of glass, varying temporally and spatially. The medieval Latin root of the English word transparent is transparare, meaning “shining through.’’⁴ The Renaissance architect Filarete, among others, describes transparent materials like glass as “diaphanous,” a word with a Greek origin meaning to “show through.” The Japanese word for transparency is izWJ (tomei). The character JS means to permeate, and fJJJ is brightness or clarity. Physics explains that when light passes through a transparent material, it slows down, giving it a shimmering quality. Light passing through a diamond travels about half as fast as it does in a vacuum — but still at over 86,000 mps.⁵ This material quality gives glass a nearly magical significance that has been noted for centuries and led to the widespread theory that transparent objects capture and hold light within themselves, as if beacons.⁶ In this way, glass enters the imagination as a materialization of light, a substantial spirituality.

Blurring of Transparency

To blur means to make the difference between two things less clear. When a night sky is photographed in long exposure, the earth’s rotation causes motion blur, an apparent streaking that resembles arched star trails. In optics, the binning of an image is related to the depth of field. When the human eye looks at an object, the object in focus appears sharp on the retina, but objects in front or behind appear blurred. As the focal plane moves within the depth of field, so do the areas that are less focused. In other words, blurring is relational and mutable. In architecture, when glass is experienced in motion under changing light, the perception of it is not simply as transparent but is a specific kind of transparency that can be called blurred. As new techniques in glassmaking have expanded the range of effects and performance of clear glass, its transparency is increasingly multivalent and complex, making nuanced differences difficult to perceive. As the perception of material becomes more blurred, the prevailing cultural and social meanings associated with glass are also blurred.

While differences between translucent — frosted glass and perforated materials that filter light and view — and clear glass are easy to discern visually, different types of clear glass are not casually distinguishable by sight, even if they possess strikingly different structural and physical properties, such as stiffness or resistance to breakage. What may be indiscernible to the eye can have a substantial impact on the overall appearance and performance of a glass building, that, in turn, impacts one’s experience and challenges prevailing meanings associated with glass. These properties can enable spatial effects and performance that were previously unobtainable and, consequently, not fully included in architectural discourse. For example, two sheets of glass, which may look identical on first glance, can behave entirely differently in how they reflect or transmit light, or how they break. Innovative approaches to heating and cooling glass buildings have resulted in optically clear buildings that are relatively energy efficient, which contradicts the prevailing reputation of glass as an energy inefficient material.

Material properties, as well as specific light conditions, inevitably blur the transparency of even the clearest and cleanest glass. Transparency is always relative, and must be considered relative to light. If color, according to Josef Albers, is the most relative medium in art,⁷ then transparency may be the most relative phenomena in architecture. In his 1935 essay “Glass, the Fundamental Material of Modem Architecture,” Le Corbusier recognized the role of light in both poetic and technical realms of glass architecture: “The lyricism that attaches to light, whether sunlight or artificial light, is always an important element to consider in relation to architecture. The stage is set for poets, just as it is for technicians.”

The angle, luminance, and intensity of light that shines through a material transforms - or blurs - the perception of transparency; this is why the same glass building can have an entirely contrasting appearance depending on the light and the time of day. Study of the day—night cycle is critical to understanding the mutability of transparency. Moreover, electric light in nighttime architecture has altered what is seen on and through glass and deserves further consideration in addition to daylight.