Glass crystalline amorphous

Tibor Joanelly

Fig. 1: Glass as a liquid in a solid state

2D presentations of [SiO4]4 tetrahedra in quartz glass (top) and rock crystal (bottom)

Fig. 1: Glass as a liquid in a solid state

2D presentations of [SiO4]4 tetrahedra in quartz glass (top) and rock crystal (bottom)

Glass is transparent, hard and precious. These properties clutter our view of a material that, on closer inspection, defies a clear physical and phenomenological description. And it is precisely in this obviously unfocused definition that glass reveals its own fascination.

The fact that we can see through glass sets it apart from other materials, makes it unusual and valuable. When we speak of glass we usually mean industrially manufactured glass in the form of vessels or windows. We forget that, for example, cellular glass loses its transparency and hence its "glassiness" during the foaming process. However, it remains a form of glass still produced - or better, recycled - in large quantities. Or glass fibres - this thread-like material developed to transmit light and data does not comply with our general idea of glass either.

Specific technical requirements have led to a huge variety of glass products. So the word glass more rightly describes a physical state rather than a clearly defined molecular material. However, in this chapter we shall speak of glass mainly in terms of the common understanding of this material and how this can be interesting for architecture.

Compared with its almost 5000-year-old history, the use of glass as a building material is a relatively recent development. The technology required to use glass in the building envelope in the form of small panes joined together was not available until the blowing iron was invented by the Romans. However, since that time glass has been available in two basic forms. The sheet glass we produce these days is based on the principle of drawing out a ribbon of molten glass. In both the ancient technique of blowing and turning the blowing iron, and today's method of levelling the glass on a bath of molten tin, the force of gravity makes a major contribution to giving the glass its form. The glass is drawn out like dough and then given its shape.

These technologies contrast with the ancient production of glass. Over many thousands of years the soft glass mass, only available in small amounts, was pressed into moulds. In order to produce hollow vessels, sand was placed in the mould and then, after the glass had solidified, scraped out again. Even today, glass objects are formed by pressing, or by pouring the molten material into moulds; the majority of glass vessels and - important for the development of modern architecture - glass bricks and blocks are produced in this way.

Astonishingly, the production of such a variety of different glass products is actually due to the structure of the material itself. In physical terms glass is in a solid state, but its structure is amorphous, not crystalline. We speak of a liquid in a solid state. At the molecular level a coherent crystal lattice is not evident; instead alternating groups of crystalline and non-crystalline molecules are seen. If we had to define the nature of glass, we would have to say

Fig. 2: Crystalline, amorphous - the microscopic structure of glass

that glass represents a dilemma. Accordingly, its use in our built environment is also Janus-like.

Out of the earth into the fire

Glass in an amorphous state is the best way of looking at its origins. The essential components of glass are quartz sand, lime and potash or soda. The natural deposits of quartz sand appear to make the discovery by mankind as almost inevitable; but coincidence must have led to a mixture of the basic constituents in a fire which produced this valuable phenomena. Glass was born out of the earth through fire.

Helmut Federle, together with Gerold Wiederin, created a work in the form of the Pilgrim Chapel in Locherboden that, besides its religious significance, symbolises the origin of glass. In their monograph on this chapel, Jaques Herzog and Pierre de Meuron describe the seemingly raw glass fragments in the alcove in the rear wall as glass in its original state: "The pieces of glass light up in all colours: orange, green, violet, white and blue. Every fragment works as an individual I ighting element. There are heavy pieces lying on top of one another, and small, delicate slivers like in diaphanous Gothic wall constructions with their intangible appearance. The light generated here is leaden and dark, light from the earth's core so to speak, from a cave, an underground gallery. Light, a blazing light, but one that is restrained with great vigour..."

The Expressionists of the early 20th century, who celebrated this new building material euphorically, promised us an all-embracing architecture with their pictorial reference to the rock crystal, an image that itself had been derived from the Gothic cathedral. Glass, as the ancient primeval material, was able to give substance to the light of the new age that was dawning.

The image of the Gothic cathedral is one of rising upwards from the earth towards God in Heaven, and the m lim m» ¡if!

ifcVtiNi h ifcVtiNi h

Fig. 5: Architectural use of glass

Pierre de Montreull (attributed): Sainte-Chapelle, Paris (F), consecrated In 1246

Fig. 5: Architectural use of glass

Pierre de Montreull (attributed): Sainte-Chapelle, Paris (F), consecrated In 1246

Fig. 4: Expressionism

Bruno Taut: glass pavilion, Werkbund Exhibition Cologne (D), 1914

Fig. 4: Expressionism

Bruno Taut: glass pavilion, Werkbund Exhibition Cologne (D), 1914

architectural use of glass is clearly visible here. The vertical sandstone structures are reduced to a minimum and the glazing gives the impression of a finer, crystallised image of the tracery framing it. We seem to be able to reach out and touch the light that penetrates the small panes of coloured glass, whereas the pointed arches of the stone structure almost crumble into the backlighting.

Glazed lattice, reflections

As described above, the use of glass in a church with Gothic tracery also represented an immense technological advance. Glass was being produced in huge quantities never envisaged before, and with the aid of a new technique, leaded lights, it could be made useful in the form of coherent panes. For the first time this valuable material, which so far had mainly been used as ornamentation, could establish itself as a veritable building material. The huge church windows also showed glass to be a complementary building material that gives the impression of a material counterweight to the massive wall. This led to the assumption that glass, like other building materials, is subject to the laws of tectonics. However, the tectonic relationship between the internal flow of forces and the external form, which is typical of most materials, cannot be proved to be similar in glass; for glass shows its inner workings a priori, or, in the words of Carl Botticher: "The artificial shape is the core shape. This means nothing more than that glass generally adopts each shape given to it and this shape cannot be incompatible with its nature. For this reason every attempt to describe glass in tectonic terms remains metaphorical."

On a microscopic level the surface of glass is finely notched. Glass is therefore a very brittle material and can accommodate hardly any tension and due to this fact it was only used for closing openings until the advent of toughened glass after the First World War. Exceptions were the glasshouses of the 19th century, which were designed in such a way that the glass in connection with the steel structure had a fake, stiffening effect. Due to the fact that in the 20th century it became possible to produce larger and larger panes of glass (at first in the form of industrially produced plate glass and from the 1950s onwards float glass) the demand for large-format panes grew as well. Glass was used quasi-structurally, mainly to form huge facade areas. As a result of the increasing use of glass, the massive, architectural object started to break up and more and more its core could be enclosed by a thin, transparent skin. Architecture presented itself in a new way, in a play of sparkling surfaces.

Very soon even the bracing elements of the glass facade were also made from glass. Italy, first and foremost, is famous for the huge expanses of glass that have become a popular means of expression in modern architecture. The architectural language that evolved incidentally

Introduction

made use of tectonic metaphors. Giuseppe Terragni's draft for the Danteum in Rome established the - up to now still unfulfilled - ideal of a sublimated architecture: the columns of this paradise are made of glass and carry a lattice of glass downstand beams which reflect only the sky..

One characteristic becomes obvious here, the one that distinguishes glass from all other building mate rials. In addition to the fact that we can see through glass, the glass surface also reflects our world. Or the surface steps back from its own body and the material - despite its transparency - awakens the impression of mysterious depth. These two phenomena seem to make glass a material without characteristics.

Science Fiction

Today, Terragni's ideal - a house made completely of glass - is conceivable from the technical point of view. Glass is no longer just for windows; it now can be produced and encoded according to specific requirements. It is quite probable that soon glass will become able to carry greater loads - through reinforcement with films or related technologies like ceramising - such that primary structural parts of buildings will become transparent. Since the 1950s this has been formulated and implemented on the scale of the pavilion. Taking into consideration the fact that facade technology has already formulated similar objectives, there is no obstacle to stop the construction of the

"all-glass" house. The sublimation of the building envelope will then be nearly complete. In this futuristic scenario it will be possible to realise every imaginable function of the racade with the aid of a sequence of different film layers. As glass can also direct light it might be possible to transform the building itself into an information medium, leading to a complete blurring of the boundaries between the virtual or media world and our physical world.

The total-media-experience glass building could transmit moods unnoticed through the optic nerve. But there is a problem: as in the movie "The Matrix" (1999) we would exist in a virtual space in which our needs would be seemingly satisfied while our physical environment could be truly miserable. If the "all-glass" building could be made habitable, e.g. by using carpets (which would be a real challenge for us architects), the futuristic scenario of total-media-experience architecture described above would itself become perverted because it would mark the end of architecture; we would be left solely with mood design, with synthetic films as information media. I can imagine a self-polymerising layer of synthetic material with corresponding optoelectronic characteristics which could be applied to any background in the form of a spray.

The near future

Maybe there will be a new chance for the glass brick. Nowadays, glass is widely used as an i nsulating material in the form of glass wool or cellular (foam) glass. Thanks

Further reading

- Archithese 6/96 "In Glas", Zürich, 1996.

- Sophia Behling (ed.): Glas, Konstruktion und Technologie in der Architektur, Munich, 2000

- Jan Hamm (dissertation): Tragverhalten von Holz und Holzwerkstoffen im statischen Verbund mit Glass, EPFL, Lausanne, 2000.

- Ulrich Knaack: Konstruktiver Glasbau, Cologne 1998.

- Thomas Kretschmer, Jürgen Kohlhoff (ed.): Neue Werkstoffe, Berlin, 1995.

- Elena Re: Transparenza al limite, Florence, 1997

- Spauszus / Schnapp: Glas allgemeinverständlich, Leipzig, 1977.

- Christian Schittich et al.: Glass Construction Manual, Basel, Boston, Berlin, 1999.

- Nicola Stattmann, Dieter Kretschmann (eds.) Handbuch Material Technologie, Ludwigsburg, 2000.

- Otto Völckers: Bauen mit Glas, Stuttgart, 1948

- Gerold Wiederin, Helmut Federle, Kunsthaus Bregenz (pub.): Nachtwallfahrtskapelle Locherboden, Stuttgart, 1997.

- Michael Wigginton: Glas in der Architektur, Stuttgart, 1996.

- English translation: Michael Wigginton Glass in Architecture, London, 2002.

Fig. 8: Dematerialised lattice

Giuseppe Terragni: Danteum project, Rome (I), 1938-4C

Fig. 8: Dematerialised lattice

Giuseppe Terragni: Danteum project, Rome (I), 1938-4C

to modern production processes it is possible to manufacture complex building elements in several operations at acceptable prices - if architectural added-value can be marketed. So why should - from the technical point of view - a structural, insulating, shaped composite brick not be feasible?

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