Development of a structural element of glass, with glass welding processes. Literature Cecile Giezen Delft, Januari 2008 Preface Within the scope of my graduation project at Delft University of Technology, department of the Building Technology, this literature study is done. This report is part of the graduation report, “development of a structural element of glass, with glass welding processes”. It is a summery of the literature about glass I have read in the beginning of this graduation process. To understand the value of the designing structural applications of glass, it is important to give insight into the background of glass. This report helps you to understand the basic principles of designing with glass. ii Index H1. History of glass ..........................................................................1 1.1 Development of glass.................................................................. 1 1.2 Glass in architecture.................................................................... 3 1.3 Development of structural glass................................................... 5 H2. Production of glass ....................................................................6 2.1 Primary manufacture................................................................... 6 2.1.2 Glassblowing ........................................................................ 6 2.1.3 Casting ................................................................................ 7 2.1.4 Drawing ............................................................................... 7 2.1.5 Float glass process ............................................................... 9 2.1.6 Glass tube production ..........................................................10 H3. Material properties of glass.....................................................11 3.1 Molecular structure of glass........................................................11 3.2 Glass types................................................................................14 3.2.1 Quartz glass (fused silica) ....................................................14 3.2.2 Soda lime glass ...................................................................14 3.2.3 Borosilicate glass .................................................................15 3.2.4 Lead glass...........................................................................16 3.2.5 Aluminosilicate glass ............................................................16 3.2.6 Glass ceramics.....................................................................16 3.3 Mechanical properties ................................................................17 3.3.1 Mechanical quantities...........................................................17 3.3.2 Material properties...............................................................17 3.4 Thermal properties.....................................................................20 3.5 Optical properties ......................................................................20 H4. Designing with glass................................................................22 4.1 Surface condition .......................................................................22 4.2 Loading time .............................................................................22 4.3 Area dependence.......................................................................22 4.4 Environment conditions ..............................................................23 4.5 Performing tests ........................................................................23 4.6 Safety .......................................................................................23 H5. Strengthening possibilities......................................................25 5.1 Introduction ..............................................................................25 5.2 Heat threatening of glass ...........................................................25 5.2.2 Heat strengthened glass ......................................................25 5.2.3 Tempered glass...................................................................26 5.3 Chemical strengthened glass ......................................................26 5.4 Laminated glass.........................................................................27 5.5 Limitations in strengthening .......................................................27 H6. References of structural glass .................................................28 6.1 Glass footbridge, Rotterdam .......................................................28 6.2 Yuraku-cho canopy underground, Tokyo .....................................28 6.3 Sainsbury Centre of visual arts....................................................29 6.4 Glass Tense grid structure ..........................................................29 H7. Definitions................................................................................31 H1. History of glass 1.1 Development of glass Natural glass has existed since the beginning of times. Due to volcanic eruptions and lightning strikes rock melts and afterwards cools down rapidly. The actually discovery of glass is described by Pliny (AD 23-79), an ancient- roman historian. According to him Phoenician merchants transported stones discovered glass in the region of Syria around 5000BC. The accidental discovery of glass took place while cooking pots on blocks of nitrate and in combination with the heat of the fire and the sand on the ground, the materials melted and were mixed together. This leaded to a opaque liquid. When opening the pharaohs tombs in Egypt glass beads were discovered. This proved the intentional glass manufacture. The first handmade glass dates from 3500 BC. Glassmakers learned that adding metallic compounds and minerals could result in coloured glass. Around 1500 BC hollow glass objects are made by rolling molten glass on a slab of stone. The oldest description of the glass mixture dates from 668-626 BC. It says: “Take 60 parts of sand, 180 parts of ash from marine plants, 5 parts of chalk- and you will obtain glass”. This is still the basis of the composition of glass Figure 1.1 Lotus goblet, Tutmosis III, 1500BC Around 30 BC the glassblowing process was invented. Syrian craftsmen used a thin metal tube for shaping glass. Romans began to blow glass into moulds for hollow glass objects. They also introduced glass for architectural purposes, when bluish green transparent glass was discovered around AD 100. These glass panes were cast and drawn. Molten glass was poured on a table sprinkled with sand and then stretched out by drawing with iron hooks. The technique that the Romans used was spread to northern Europe regions. During the middle ages the glassmaking technology in Europe changed. Due to difficulties of importing raw materials in northern Europe, soda glass was replaced by glass made out of potash from the burning of threes. Between Northern Europe and the Mediterranean area the glass differed from composition. Around AD 1100 a German craftsman discovered how to make flat glass by making a hollow cylinder of 3m and a diameter of 45cm. A hollow sphere was blown and put in a pod for shaping the cylinder. The ends of the pod where cut off, the cylinder was cut in its longitudinal direction and spread out. 1 Another technique was blowing a glass ball and then opening it at the opposite of the pipe. When spinning the semi melted glass it flattened and increased in diameter size. This glass is called crown glass. In contrast to cylinder glass, crown glass was more even and more lustrous. This was also the time when stained glass windows are made. Every glass pane was surrounded by lead strips and joined together. The gothic cathedral with his big window panes is the best example of that time. Figure 1.2 Glass blowing in early years Figure 1.3 Crown glass In the 15th till the 17th century the most important glass industry was built in Venice and especially on one of the islands of Venice, Murano. Still famous about its glass craft. It was the major producer of drinking glasses, bowls and mirrors. The success of the Venetian glass was due to the absence of colour. Adding brownstone and soda from the sea weed to the raw materials made the glass transparent and soft. In the 17th century an English glassmaker Ravenscroft developed lead crystal. This glass has a high refractive index and therefore a brilliant surface. In France a new process was developed for the production of glass plates. The molten glass was spread out on a preheated copper table. It was pressed by a water-cooled metal roller. The pane sizes were 1.2mx2m. In this period glass endured a booming phase. Glass was not only sold to churches and monasteries, but also for houses and palaces. During the industrial revolution, mainly in the later states, the mechanical technology of glass developed. The relationship between the composition of glass and the physical qualities became clearer. On of the most important glass maker is Otto Schott. He did research on the optical and thermal properties of glass by adding chemical elements to the basic mixture of glass. Toward the beginning of the 20th century Michael Owens invented the automatic bottle blowing machine. And the Belgian Fourcault developed a way of drawing sheets for window glass. This glass was drawn vertically, while in the end of the first world war, another Belgian Bicheroux, developed a method where molten glass was pored through two rollers. This leaded to a more constant thickness.