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IELTS READING – Sheet glass manufacture: the float process S42AT1
IELTS READING S42AT1
Sheet glass manufacture: the float process
Glass, which has been made since the time of the Mesopotamians and Egyptians, is little more than a mixture of sand, soda ash and lime. When heated to about 1500 degrees Celsius (°C) this becomes a molten mass that hardens when slowly cooled. The first successful method for making clear and flat glass involved Q1 spinning. This method was very effective as the glass had not touched any surfaces between being soft and becoming hard, so it stayed Q2 perfectly unblemished, with a ‘fire finish’. However, the process took a long time and was Q3 labour intensive.