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Soda-Lime Float Glass

Economically priced sight-glass grade material

Special Properties

  • Low-cost flat-glass
  • Clear transparency under normal lighting conditions
  • Reasonable hardness

Typical Applications

  • Sight-glass windows
  • Simple front windows without optical function
  • Mechanical glass parts
  • Protective glasses
  • Thin sight-glasses

Related glass types

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Soda-lime float glass for sight glass applications

Soda-lime-silica float glass materials with sight glass quality are ideally suited for all applications that don't require optical grade surfaces or a high flatness and material purity. The glass is consisting of about 71% silica. To lower glass-transition temperature, sodium carbonate ("soda") is added, which increases the water-solubility of the glass. To avoid this unwanted effect, also calcium oxide ("lime"), magnesium oxide, and aluminum oxide are added, to gain back chemical durability partially. The result is a low-cost glass with a lowered melting temperature, which can easily be processed, and that is suitable for all kinds of commercial applications with moderate requirements.

When looking with the naked eye, the glass looks high-quality, and there are no significant defects or inhomogeneities in the glass when looking through it. However, this type of soda-lime-silica glass materials do not achieve the excellent surface quality and optical flatness of our iron-reduced selected float glass, and its physical purity is not as high. For example, with soda-lime glass with sight glass quality, a slight grey haze can become visible under strong lighting conditions. However, this effect is not perceived under normal lighting conditions, and it has almost no effect on the transmission. About 90% of the visible light is still transmitted, which is only less 1% compared to our selected float glass.

Our low-cost soda-lime sight glass has the ideal properties required for less sophisticated applications like glass covers, simple front glasses, sight-glasses, or protective glasses. It is a low-cost material used for all non-optical applications that do not need a high chemical or thermal resistance and that do not need to withstand an increased operating temperature.


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Due to the properties of soda-lime glass materials, we do not recommend the use at high thermal load or in harsh chemical environments. If you are in search of a glass type with excellent chemical properties and increased temperature resistance, please take a look at our borosilicate glass data-sheet.





Refractive Index

  • Approx. 1,52

Mechanical Density

  • Approx. 2,5 g/cm3

Coefficient of Thermal Expansion

  • Approx. 87 x 10-6/K

Typical Glass Composition of Soda-Lime Glass
(rough average values*)

  • SiO2 (silica / silicon dioxide): 71%
  • Na2O + K2O (sodium oxide + potassium oxide): 14%
  • CaO (calcium oxide): 8,6%
  • MgO (magnesium oxide): 4,4%
  • Al2O3 (aluminum oxide): 1,3%
  • Fe2O3 (ferric oxide): 0,1%
  • SO3 (sulfur trioxide): 0,3%

Available Glass Thicknesses

Since soda-lime-silica float glass is not an optical glass, all specifications above are subject to inevitable fluctuations. Therefore, all specifications are only rough approximations.

*The glass composition can fluctuate from batch to batch. The percentages given are only typical averages and therefore do not add up to exactly 100%.


All given details and specifications are mean reference values and are not guaranteed. Also, please consider the "Notes on technical specifications".


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