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Heat Absorbing Filters KG1, KG2, KG3, KG4 & KG5


Special Properties

  • Very broadband heat blocking range
  • Absorbs infrared energy
  • Transparent for visible light
  • Almost angle independent transmissivity
  • Can be thermally hardened for higher operating temperatures
  • Largely color neutral
  • High optical density for infrared radiation

Typical Applications

  • Heat absorbing glass filters in lighting systems
  • Sensor technology
  • Infrared absorbers
  • Heat protection filters
  • Protective filter for projector optics

Request for Quotation


SCHOTT glass filters KG1 - KG5 allow the absorption of thermal energy. They are called heat absorption filters because they absorb heat due to their high optical density in the infrared wavelength range. Hence, the glass filters are often used in lighting systems to absorb heat emitted from a light source. At the same time, the glass filters offer a high, relatively color-neutral visible light transmission. The filter optics are heated during operation by the absorbed heat energy. Therefore, the heat can be removed from a lighting system by direct cooling or ventilation of the KG glass filter. If heat-absorbing filters must withstand higher operating temperatures, it is recommended to thermally harden the filter glass after polishing and shaping.

Our high quality KG glass filters are fabricated from original SCHOTT raw filter materials which exist as unpolished filter-squares or as unpolished rolled filter materials. The heat-absorbing filters are ground, polished and formed to customer specifications. Please use our inquiry form to request a quotation for your custom-made heat absorbing filter.


How can I order the heat absorbing filters?

All polished optical glass-filter optics at dimensions at up to 50 mm x 50 mm and below and at thicknesses of 1,00 mm, 2,00 mm or 3,00 mm typically ship within one working week. To get a quotation for a KG-heat absorbing filter, please click the button below:


Request for Quotation



NEW! Our SCHOTT-Filter Online Calculator

Visit our online SCHOTT-filter calculator for the analysis of the transmission of all available color glass filters made of SCHOTT filter material. The calculator is online at your free disposal. You can compute individual filter transmission curves and choose to see the internal transmittance, or the external transmittance of the glass filters including surface reflection losses.



Enlarge transmission of KG1, KG2, KG3, KG4 and KG5
IR-absorbing glass filters at 200-1100 nm

Enlarge internal transmission at 1000-4600 nm



  • Original SCHOTT KG1-KG5 filter glass material


Thermal Tempering

  • minimum filter glass thickness for full thermal tempering: 3 mm


  • Depending on filter material and thickness of the filters
  • Other on request

Surface Quality

  • typ. 80-50 scratch & dig (MIL-0-13830A)
  • Other on request

Max. Dimension

  • 164 mm x 164 mm (square filters)
  • ø 150 mm (diameter filters)
  • larger filter sizes possible at large quantities

Further detailed information about all KG-glass filter products are available on request.


All given details and specifications are mean reference values and are not guaranteed. In addition, please consider our "Notes on technical specifications"