8. GLASSES M. Clara Gonçalves Departamento de Engenharia de Química Instituto Superior Técnico Universidade de Lisboa Av. Rovisco Pais, 1049-001 Lisboa, Portugal Tel.: 351 21 8419934 Fax: 351 21 8418132 E-mail:
[email protected] Abstract In architecture, glass established itself as an element that provided cohesion between the inside and the outside. Glass is a transparent structural material and one of the few building materials that combines tradition with technological innovation. Glass is a product that harmonizes colour, reflectance, transparency or opacity, texture and thickness, flatness or curvature with, for example, some control over opacity or self- cleaning properties, whilst at the same time being low-emissive, heat and/or sound insulator, offers protection and security, as well as resistance to thermal shock and impact from projectiles. Moreover glass is the only material that is 100% recyclable, what we should bear in mind, as sustainable development is only possible by careful use of resources and technology. Glass is, definitively, a hard product to beat. Outline 1. Glass in construction and architecture: brief history 2. Glass composition and structure 2.1 What is glass? 2.2.1 Zachariasen rules or crystallochemical theory 2.2 Raw materials 3. Glass technology 3.1 Melting, homogenization and fining 3.2 Flat glass forming techniques 3.2.1 Roman glass 3.2.2 Medieval glass 1 3.2.3 Crown glass 3.2.4 Colburn-Libbey-Owens Glass 3.2.5 Fourcault-Pittsburgh glass 3.2.6 Float glass 3.3 Annealing 3.4 Flow chart of float glass production process 4.