I'm looking to use an epoxy in a high-temp environment like 800C, and one that is optically transparent at 450nm (not below 90% transmission). But i'm having trouble finding one. It can be made of any material, as long as it can be cured in a mold.

  • $\begingroup$ Are you using the epoxy as just an edge sealant/adhesive or is the epoxy going to be some kind of surface/ window ? If the latter you should use a high temp glass, the technology for molding glass is well established. $\endgroup$ Sep 24, 2018 at 23:49
  • $\begingroup$ What's the application? Perhaps there's another solution. $\endgroup$
    – Farris
    Mar 17 at 12:53

2 Answers 2


since cured epoxy is a carbon-based polymer, you will have a very hard time finding one that can stand 800C. Have you considered a sintered ceramic?

  • 2
    $\begingroup$ With 90% optical transmission? $\endgroup$
    – Solar Mike
    Sep 25, 2018 at 4:30
  • 2
    $\begingroup$ Yeah, near-100% fully dense and optically transparent sintered ceramics have been around for ~40 years. Not used much but they do exist. $\endgroup$ Sep 25, 2018 at 7:25
  • $\begingroup$ I want to see some of this mythical material $\endgroup$
    – DKNguyen
    Nov 17, 2021 at 14:54
  • $\begingroup$ A link to an example material would improve this answer. $\endgroup$
    – Eric S
    Jul 16 at 1:30

You will need to go for glass and casting.

High temp silicones and epoxies don't go to 800 deg C and they are not clear anywhere near their high temperature variants. Closest I know is a murky clear "crystallized silicone" that goes to 900 deg F.

Ceramic "adhesives" are granular and won't be clear.

Molten glass and a mold are the closest for your optical and temperature needs. You might be able to get away with pressurizing and heating a powdered glass (aka a silica ceramic) to try and make it clear, but 90% optical transmission is pretty demanding to the point where something molten might be required.


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