Cabell County Glass Project 03 - Making Glass

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Making Glass
Ingredients
Silica
Soda Ash
Lime
Metal Oxides
Glass Making Processes
General Process
Plate Glass Production
Types of Glass
Soda-Lime
Lead Crystal
Flint Glass
Borosilicate
Safety Glass
Laminated Glass
Ballistic Glass

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Cabell County Glass Project 03 - Making Glass

  1. 1. Glass Industry in West Virginia Making Glass An Interdisciplinary Project of Cabell CountySchools and Marshall University’s June Harless Center Session 3 – 18 April 2013
  2. 2. Outline• Making Glass – Ingredients • Silica • Soda Ash • Lime • Metal Oxides – Glass Making Processes • General Process • Plate Glass Production – Types of Glass • Soda-Lime • Lead Crystal • Flint Glass • Borosilicate • Safety Glass • Laminated Glass • Ballistic Glass18 April 2013 Session 3 2
  3. 3. Glass• Contrary to common misconceptions, glass is NOT a liquid• It does not slump in old windows• Because of the molecular arrangement during cooling, glass does not form distinct crystals and is classified as an amorphous solid18 April 2013 Session 3 3
  4. 4. Crystalline Solid Amorphous Solid18 April 2013 Session 3 4
  5. 5. Ingredients• Glass is produced with simple ingredients: – Silica (often about 70%) from sand – Lime – Sodium oxide from lime by the Solvay process – Cullet (recycled glass) – Metal oxides18 April 2013 Session 3 5
  6. 6. Metal Oxides• Calcium oxide (quicklime), magnesium oxide and aluminum oxide strengthen the glass• Lead oxide, barium oxide, thorium oxide and lanthanum oxide increase the refractivity of the glass producing a more brilliant glass• Sodium sulfate, sodium chloride or antimony oxide is added to reduce the air bubbles in the glass• Iron may be added to glass to increase heat absorption• Boron oxide may be added to glass to provide protection from cracking during changes in temperature18 April 2013 Session 3 6
  7. 7. 18 April 2013 Session 3 7
  8. 8. 18 April 2013 Session 3 8
  9. 9. 18 April 2013 Session 3 9
  10. 10. Glass Making Process• Glass making requires several furnaces• A small furnace preheats the ingredients for glassmaking• An ancillary furnace warms the ceramic forms for the glass• The hottest furnace melts and mixes the materials• A small furnace anneals and cools the formed glass18 April 2013 Session 3 10
  11. 11. Glass Furnace18 April 2013 Session 3 11
  12. 12. Plate Glass Manufacturing• Broad sheet glass production• Cylinder glass production• Blown glass production• Crown plate glass• Rolled glass• Float Glass18 April 2013 Session 3 12
  13. 13. Blown Plate Glass• Broad sheet glass production – a cylinder of glass was blown then cut into a sheet that was cooled on an iron plate• Cylinder glass production – similar to broad sheet glass except that a larger cylinder was blown into an iron mold that was cut and cooled on an iron plate. This process was used by William Blenko to make stained glass• Blown glass production – starts with broad or cylinder glass but is polished on one or both sides18 April 2013 Session 3 13
  14. 14. 18 April 2013 Session 3 14
  15. 15. 18 April 2013 Session 3 15
  16. 16. Crown Glass• Crown plate glass - glass was blown into a hollow iron globe that was flattened by spinning to make a disc18 April 2013 Session 3 16
  17. 17. Crown Glass18 April 2013 Session 3 17
  18. 18. Because crown glassdoes not haveuniform thickness,people assume thatthe glass hasslumped over time.Early glaziersnaturally put thethicker side of theglass in the lowermullion.18 April 2013 Session 3 18
  19. 19. Float Glass• Melting point of glass 1500o F• Melting point of tin 450o F• Molten glass at 1500o F is poured onto a shallow pan of hot molten tin. The glass harden as it cools and is passed to an annealing oven where the glass sheet gradually cools and is cut to desired sizes18 April 2013 Session 3 19
  20. 20. 18 April 2013 Session 3 20
  21. 21. 18 April 2013 Session 3 21
  22. 22. Types of Glass• Soda-Lime• Lead Crystal• Flint Glass• Borosilicate• Safety Glass• Laminated Glass• Ballistic Glass18 April 2013 Session 3 22
  23. 23. Soda-Lime Glass• Typical glass from which most tableware, art glass and plate glass is manufactured• 75% silica with Na2CO3, Na2O, CaO, MgO and Al2O3• Over 90% of all glass is soda-lime18 April 2013 Session 3 23
  24. 24. Soda-Lime Glass18 April 2013 Session 3 24
  25. 25. Lead Crystal• Lead crystal has a composition similar to soda- lime glass except PbO (at least 24%) replaces the CaO giving the glass a high reflectivity and index of refraction. Waterford and Steuben are well known makers of lead crystal• Modern “lead crystal” has BaO, ZnO or K2O rather than PbO since lead is a biological hazard18 April 2013 Session 3 25
  26. 26. Lead Crystal18 April 2013 Session 3 26
  27. 27. Flint Glass• Formerly had up to 60% PbO to increase the index of refraction for scientific lenses.• Modern flint glass lenses have TiO2 or ZrO2• Called “flint glass” for the flint stones found among the silica deposits in England were glass was produced in the 1600s18 April 2013 Session 3 27
  28. 28. Flint Glass18 April 2013 Session 3 28
  29. 29. Borosilicate Glass• has high levels of B2O3 to soda-lime glass mixture that raises melting point, increases ability to withstand thermal shock and strengthens the glass.• Pyrex, Kimex and others scientific and kitchen glassware are borosilicate glass18 April 2013 Session 3 29
  30. 30. Borosilicate Glass18 April 2013 Session 3 30
  31. 31. Safety glass• Tempered or toughened glass is produced by controlled heating creating internal stress that causes the glass to break into small crumbles rather than jagged shards when broken• Tempered glass is required in doors and many windows18 April 2013 Session 3 31
  32. 32. Tempered Glass18 April 2013 Session 3 32
  33. 33. Laminated Glass• Laminated glass couples toughened glass with a layer of plastic to contain the broken crumbles of glass18 April 2013 Session 3 33
  34. 34. Ballistic Glass• “Bulletproof” glass is made from a combination of hard and soft glass layers. All layers must have the same index of refraction.• Recent innovations allow a transparent plastic layer to be adhered to the inside of traditional glass to provide resistance to penetration from a projectile18 April 2013 Session 3 34
  35. 35. Ballistic Glass18 April 2013 Session 3 35
  36. 36. Supporters

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