Quarry Southern Africa November 2018 - Page 34

BENEFICIATION The Eiffel Tower is due to get a protective bullet resistant barrier to deter terrorist attacks. the products of this exclusive industry within the reach of 'the ordinary man in the street'. The ubiquity of glass on Roman archaeological sites is testimony to its ability to span the gap between the disparate geographical and social elements of the Roman Empire. Why do we make glass? The uses of glass are many and varied, with each manufactured using a different technique: • Glass containers: in which glass is carefully made in three different stages (melting of raw materials, pouring or blowing glass in container moulds and cooling with finishing touches for quality). • Float glass processes: in which glass is laid on the surface of molten metal (tin or lead). This process is used for creating of flat windows. • Manual glass blowing: used mostly for creating of art objects and custom glass containers. • After manufacture, every glass product can be additionally treated by coating, heat treating, engraving or some kind of decorating. • Toughened glass: this type of glass is tempered, may have distortions and low visibility but it breaks into small dice-like pieces at modulus of rupture of 3 600psi. Hence it is used in making fire resistant doors. They are available in the same weight and thickness range as float glass. • Laminated glass: this type of glass is made by sandwiching glass panels within a protective layer. It is heavier than normal glass and may cause optical distortions. It is tough and protects from UV radiation (99%) and insulates sound by 50%. Used in glass facades, aquariums, bridges, staircases and floor slabs. • Shatterproof glass: by adding a polyvinyl butyral layer, shatter proof “Though glass is today one of the most common building materials for windows, as well as many ornamental objects and computer communications, its initial use by our earliest ancestors was as a sharp weapon and useful tool.” 34_QUARRY SA| NOVEMBER/DECEMBER 2018