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Minerals Industries
Published in Charles E. Baukal, Industrial Combustion Pollution and Control, 2003
There are five main steps in the manufacture of glass: mixing, melting, forming, annealing, and finishing. Mixing is either wet or batch agglomeration, depending on the type Both minimize dusting and the resulting particulate emissions, ensure homogeneity, and increase melting efficiency and glass quality. Melting of small quantities is done in pot furnaces or crucibles. Larger quantities of glass are melted in refractory-lined furnaces that usually incorporate some type of heat recuperation. Forming varies by the type of product. Glass bottles and jars are typically formed in automatic machines. Pressing is used to form flat items such as lenses and plates. Drawing and casting are used to mold molten glass. The products are then slowly cooled or annealed, usually in a long oven called a lehr. Annealing reduces the internal stresses that could cause the glass products to crack. The two types of finishing processes are mechanical and chemical. Mechanical processes include cutting, drilling, grinding, and polishing. Chemical treatments are used to alter the strength, appearance, and durability of a product. Once finished, the products are cleaned with some type of solvent, which may be aqueous, organic, or halocarbon.
From Georgian traders to Victorian glass makers: The evolution of the Chance family business and its role in developing glass manufacturing
Published in The International Journal for the History of Engineering & Technology, 2021
Towards the end of the eighteenth century there was a development in the broad glass process that originated on the borders of France and Germany. This created the glass using the cylinder process but the cylinders were allowed to grow cold before the ends were removed and the cylinder slit down the length. The glass was then reheated, flattened and slowly annealed in an annealing tunnel or ‘lehr’. Various experiments were made by British glass companies to compete with this product. Cooksons on the Tyne introduced ‘blown plate glass’, which appears to have been glass made by the cylinder method and then polished on one or both sides. In an early case of technology transfer, George Ensell claimed that he ‘had fiddled into Germany and returned possessed of the secret’13 of the ‘German’ process. He provided samples of the glass produced by this process to a meeting of the Society of Arts in January 177814 where it was given an enthusiastic reception. Despite this accolade, this glass was not accepted by the market and production soon ceased.