Material opaque to IR but transparent to visible light

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Discussion Overview

The discussion revolves around the search for a polymer that is opaque to infrared light while remaining transparent to visible light. Participants explore the feasibility of such materials, potential alternatives, and specific applications related to infrared cameras.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the existence of a polymer that absorbs infrared wavelengths above 700 nm but allows visible light to pass through without significant absorption.
  • Another participant suggests using glass with a blue filter as a potential solution, prompting questions about the specifics of the blue filter material.
  • A participant expresses interest in using Copper II sulfate on glass as a method to achieve the desired effect, questioning the viability of this approach.
  • There is a discussion about the difference between absorption and reflection of infrared light, with references to "hot mirrors" as a possible alternative.
  • Participants seek clarification on the specific range of infrared light being targeted for absorption.

Areas of Agreement / Disagreement

The discussion features multiple competing views regarding the materials and methods that could be used to achieve the desired optical properties. There is no consensus on the best approach or the effectiveness of the proposed solutions.

Contextual Notes

Participants have not fully defined the specific infrared range of interest, and there are assumptions about the properties of colored filters and materials that remain unverified.

refind
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Hi all,

I want to get some sort of polymer that is opaque to infrared (absorbs wavelengths above 700 nm very well) but transparent to visible light (does not absorb much light below 700 nm).

Does this even exist without being a meta material?
 
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What's wrong with glass with a blue filter on it?
 
Thanks. What is the blue filter? What material is it, are there any links you can point me to? I appreciate it.
 
refind said:
Hi all,

I want to get some sort of polymer that is opaque to infrared (absorbs wavelengths above 700 nm very well) but transparent to visible light (does not absorb much light below 700 nm).

Does this even exist without being a meta material?

Is there a reason you want it to absorb instead of reflect (google 'hot mirror')?
 
refind said:
What is the blue filter?

It is a light filter that is blue. If you Google "blue filter" there are 610 million hits.
 
Andy Resnick said:
Is there a reason you want it to absorb instead of reflect (google 'hot mirror')?

Hot mirror is a great suggestion. I just want to make an area invisible to an IR camera but visible to a normal camera.

By the way I was googling around and someone says to spray Copper II sulfate on a piece of glass and that will do the trick. I don't mind the blueish tint and I might give it a try. Does it sound like a bad idea?

Vanadium 50 said:
It is a light filter that is blue. If you Google "blue filter" there are 610 million hits.

I didn't know blue colored plastic/glass will necessarily absorb IR. Thought it would just absorb visible red. I'll give those a try too, got an infrared LED I could see with my phone camera to test it out.
 
Last edited:
What range of IR?
 

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