SCHOTT FAQ: Frequently Asked Questions And More Glass FAQs

1. How is the prescribed strength of eyeglasses achieved?
Refraction can be varied by the refractive index of special types of optical glass, as well as by grinding, and thus can be used as a compensating strength for defective vision, namely in the form of eyeglasses. There are over 120 different types of optical glass.
2. What are the main components of glass? In what ratio are the main components mixed?
about 60 parts sand = 24%
about 180 parts potassium carbonate = 74%
about 5 parts lime/chalk = 2%

according to one of the first formulations handed down from Assyria (about 640 BC) Additives, metals and rare earths are used to obtain coloring and other properties

3. How is glass produced?
Glass is melted in vats with fireproof cladding, which are heated by oil, gas or electricity, and then

a) drawn, rolled (flat glass)
b) pressed, blown (hollow glass)

and, if necessary, subjected to further processing:

a) coated
b) imprinted
c) polished
d) drilled
e) faceted
f) frosted
g) tempered/pre-stressed

4. How is white flashed opal glass made?
White flashed opal glass is made by frosting clear glass, or made as frosted translucent glass or as clear glass with white screen printing.
5. How is colored glass made?
Glass that is colored throughout can be produced by adding coloring materials, subsequent colored coating or transparent imprinting is also possible
6. At what temperatures does glass begin to melt?
Depending on the type of glass and on the glass batch composition the melting temperature is between approximately 1000 °C and 1600 °C (1832 °F and 2912 °F).
7. When was glass first produced?
Historically, glass production is known to have existed in ancient Egypt around 8000 BC, as well as in Mesopotamia and Mycenaea, China and Northern Tyrol
8. How is reflective glass made?
Reflective glass can be produced by vaporizing, coating or imprinting with metallic materials, such as silver, gold, copper, etc.
9. Why does glass protect against UV rays?
Special glass or vaporized glass has a blocking filter in the UV range, which reduces or blocks the penetration of UV rays.

18. What does a glassblower's pipe look like?

SCHOTT FAQ glassblower
19. What is cast glass?
Cast glass designates a family of glass produced in a casting production process. It includes raw glass, figured glass, horticultural cast glass, wire-reinforced glass and wire-reinforced figured glass. It is also possible to produce colored cast glass.

20. How are mirrors produced?
Mirrors are produced by coating the rear side of flat glass with
  • silver
    • copper
      • or other reflecting materials.

The reflecting layer is additionally protected and lacquered with a coating. decklackiert.
21. What is flashed opal glass and what is it used for?
Clear flat glass, which is coated and melted together with a thin opal glass (white) during drawing, is called flashed opal glass. Covers for lighting units for glare-free lighting, display cases and indicator glasses in instruments are only some of the applications.

22. What is the economic significance of the glass industry in the industrialized countries?

The glass industry occupies an important position as an economic factor worldwide, but particularly in the industrialized countries:
  • Container glass 44%
    • Flat glass 29%
      • Specialty glass worldwide
        • + technical glass 15%
          • Glass fiber 12%

This structure represents a gross production value totaling DM 130 billion (approx. $82.3 billion), incl. processing, improving, etc.

Specialty glass - production values in the most significant regions (total: DM 14.8 billion or $9.3 billion) exclusive of Eastern Europe and China

  • North America DM 4.3 billion ($2.7 billion)
    • Western Europe DM 3.7 billion ($2.3 billion)
      • Japan DM 2.8 billion ($1.8 billion)
        • Southeast Asia + Far East DM 3.3 billion ($2.1 billion)
          • Others DM 0.7 billion ($0.4 billion)

23. How is glass coated?
The coating of glass surfaces, in accordance with state-of-the-art processes, ensures even the most complex coating. This plays a great part in glass lenses for eyeglasses, display window glass, decorative glass.
The "SCHOTT Technical Glasses Guide" contains general information and answers to SCHOTT glass FAQs for the determination and evaluation of important glass properties and also informs about specific chemical and physical characteristics and possible applications of the commercial technical glasses produced by SCHOTT. With this brochure we intend to assist scientists, engineers, and designers in making the appropriate choice and optimum use of SCHOTT products.
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