Dewar Flasks

Fredericks is a leading manufacturer of glass Dewar flasks. These flasks are used in advanced applications such as infrared detector assemblies, thermal imaging systems, and optoelectronics instrumentation. Fredericks Dewar flasks are constructed utilizing many forms of glass-to-glass and glass-to-element sealing. Specialized techniques have been developed for sealing many uncommon materials, including Kovar, sapphire, germanium, and platinum.

Precision grinding, polishing, and sealing equipment have allowed Fredericks to achieve tolerances to less than .001”. Repeatability to the tightest specifications is a hallmark of Fredericks Dewar flasks. Stringent quality control procedures assure consistent performance.


  • Vacuum integrity assured through flawless hermetic sealing
  • Tolerances to less than .001”
  • Simple glass-to-glass configurations to highly elaborate glass-to-metal multi-element units
Outside Diameter .50” to 1.50” (12.70 mm to 38.10 mm)
Inside Diameter .125” to 1.0” (3.175 mm to 25.40 mm)
Length .75” to 6.0” (19.05 mm to 152.40 mm)

Fredericks also offers complete custom Dewar flask fabrication, including:

  • Glass-to-sapphire sealing (dome shape or flat sapphire windows)
  • Automatic grinding and polishing
  • Automatic molding/sealing including multi-element lead patterns
  • Graded seals