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Dr. Nazetaro’s Lesson ”Basics of Optical Glass”

How to manufacture Optical Glass　- Manufacturing -

  • Matt
    Doctor, tell me about the process after blending.
  • Naze Taro
    Sure. The next step is to melting. Melting glass requires very high temperature.
  • Matt
    I watched a TV program showing glass factory. That was not an optical glass factory, but it still looked very hot. And also, the melted glass looked thick.
  • Naze Taro
    Glass isn’t characterized as either a liquid or a solid, but something in between called a fluid.
  • Matt
    Really? I thought that glass was a solid.
  • Naze Taro
    The combined raw materials are melted with the optimum melting method for the type of glass being made. SUMITA uses crucibles made of platinum to melt glass materials.
  • Matt
    Platinum… the metal used for jewelry? It must be very expensive.
  • Naze Taro
    Exactly. Melting temperature is as high as from 1200 to 1400℃ (2192-2552°F), and if a crucible cannot withstand the temperature, the glass material is likely to be contaminated by impurities originating from the crucible material. Crucible made of platinum can withstand very high temperature.
  • Matt
    I never thought SUMITA’s factory would have that expensive facilities.
  • Naze Taro
    Hahaha, just in case, the crucibles are strictly guarded with the theft prevention system. Also, while the crucibles are not used for operation, they are stored into bank’s safety-deposit box.
  • Matt
    That’s good to know.
  • Naze Taro
    Let’s get back on track. The melted glass is slowly cooled and turned into various shapes. If the blending was not good enough, the glass material crystallizes while being cooled, becomes opaque and looks like a stone, which is not what we’re looking for.
  • Matt
    OK, so this is the end of making optical glass?
  • Naze Taro
    No, the melted glass needs internal inspection. Defects such as bubbles and striae are removed from the glass block by inspectors’ eyes. This process concludes optical glass block manufacturing.
  • Matt
    Each block is inspected by human eyes?
  • Naze Taro
    Yes, a high level of skill is required for this operation, and this keeps our products’ quality high.
  • Matt
    Great. Thank you, Doctor!
  • Naze Taro
    You’re welcome! We will learn about lenses next time.
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