Wednesday, April 20, 2011

Infrared and Ultraviolet Transmission in Plexiglass Acrylic and Makrolon Polycarbonate Sheet

Well, this explains everything. I finally got my hands on the charts to show UV, Visible, and IR light transmissions in Plexiglass sheet. And, I learned something new today: IR or InfraRed light varies in transmission logarithmically depending on the thickness of the Plexiglas sheet. And, it's not a smooth curve. There are areas of filtered transmission. This explains why the IR remote on my entertainment center works like a champ on the TV and DVR but sucks on the audio amplifier (which has a different IR band). (I am using frost acrylic) (update 8/11 - replaced the panels with the IRT acrylic - it's opaque black but the IR bands are all working for all the equipment!!)

Before sharing the charts, let's think about UV and IR and visible "light".
1. You cannot SEE this type of "light".
2. You can feel the IR - it warms you up.
3. You can't see or feel UV, but your skin will fry if exposed too long, and paper, artwork, fabrics, and other materials will degenerate from exposure.
4. IR is heat, and we can capture heat images in a CCD or IR film - way cool to see.
5. IR can penetrate opaque material. UV cannot.
6. Visible light transmission through clear Plexiglas is 92%. You cannot detect the 8% loss - it looks clearer than water. You lose 4% reflected off the front surface and 4% off the INSIDE of the back surface. If I put a business card at the end of a 4" thick piece of Plexi 8 ft long, you could read it perfectly.

OK - the charts - check this out!

Your UV and Visible Light chart - you can see the natural drop of UV filtering from standard Plexiglas, and then the extra filtering of the UVF and UVT grades. Plexiglas MC is your standard general purpose extruded  sheet, and Plexiglas G is cell-cast acrylic sheet. Plexiglas UF5 is the standard extruded "MC" with a UV filtering additive. UF3 is the version from "G" cell-cast acrylic.

Now the IR light transmission for CLEAR Plexiglas:

According to the makers of Plexiglas®:

Colorless Plexiglas® sheet sheet transmits most of the invisible near-infrared energy in the 700 to 2,800 nanometer region, but it also absorbs certain bands as shown. The curves for 0.118 inch and 0.944 inch thick colorless Plexiglas® sheet show that near-infrared transmittance depends on thickness, decreasing logarithmically as thickness increases.

At infrared wavelengths longer than 2,800 nanometers and as long as 25,000 nanometers, and in thicknesses greater than 0.118 inch, colorless Plexiglas® sheet is entirely opaque. At thicknesses less than 0.118 inch, Plexiglas® sheet transmits small amounts of infrared energy at certain wavelengths within this region. All standard formulations of colorless Plexiglas® sheet have the same general infrared transmittance characteristics.

Sensitive instruments confirm that weathering produces no change in the infrared transmittance characteristics of Plexiglas® sheet.

But wait, there's more! Here's the special grade of Infra-Red Transmitting sheet. It is BLACK in color, but allows the IR to transmit through. Very cool for spy related video equipment. Available in 1/8" and limited amounts of 1/16" thick.

1146 is the IRT and 199-0 is opaque black. They look identical but obviously are not....

But wait.... there's more!
Here's the chart for POLYCARBONATE sheet - known as Lexan, Tuffak, Makrolon etc.  Note that polycarbonate goes opaque in the UV spectrum and has good IR transmission.


  1. question : Over time will UV light breakdown plastics having the effect of transmitting more UV light? If so would the UV light have the opposite effect on plastics created to permit UV light ? ie. Animal habitats, Solariums, and Tanning bed acrylics?

  2. OK - good question! Acrylic is naturally UV-resistant. So no worries about breakdown. The main application for this formulation is sun-tanning beds.

  3. Hi Genius

    what is the number of the Lexan IR pass material, I have used it in the past for IR Illuminators my company makes, but I have lost the number of it and where to get it, I need the Lexan and not the plexiglass version

    IR Guy

  4. Any idea about transmittance above 2200nm for Polycarbonate? I hope to use it as a filter for light in the 10,000-11,000nm range.

  5. thanks for the awesome write-up. do you know of a filter that can block all (or almost all) visible and transmit only the IR from a 1000W tungsten lamp? i *want* only the IR, and i want to throw away the visible light.


    1. The 1146 should do that. No visible light

  6. dear sir i need a filter that can pass sun light wavelength of 1-1240 will it cost per square meter.what are the materials you use to make it please inform me at my mail :

  7. Hmm - I don't know of a material existing right now with 1nm to 1240nm transmission. Tall order. Maybe can be made... What is the application?

  8. I need a product that will allow the light from the IR LED's on my new back up camera to pass, what product do you recommend?

  9. Do you have a recommendation on a plastic that would be good for simple gears (in a toy) and nearly opaque to 940nm?

  10. i need a filter that can
    pass sun light wavelength of
    1-1240 will it cost
    per square meter.what are the
    materials you use to make it
    please inform me at my mail :
    Plastic Genius October
    22, 2012 10:34 AM
    Hmm - I don't know of a
    material existing right now
    with 1nm to 1240nm
    transmission. Tall order.
    Maybe can be made... What is
    the application?
    how is cost for 1 square metre ?(transmittance 500-1200 nm)

  11. What would be your recommendation of multiwall/honeycomb product/s for achieving maximum IR & near IR transmission for a solar thermal application?

    While the highest transmission will obviously come from a single-wall sheet, the multiwall/honeycomb requirement is in order to minimize conductive/convective losses at the cost of some transmission loss.

  12. I am making a LED interactive modular floor for which I would be using IR sensors (emitter+photodiode). I would be using plexiglass. I just wanted to know how could i avoid the interference of the other IR radiations in the room?

  13. Great info. How about a plastic that will absorb (not reflect)most IR but either efficiently transmit or reflect visible (UV is good too, but not essential)?

  14. Is there a maximum distance an infrared sensor can be set back behind the plastic window using the 1146 without effecting the sensor performace?

  15. This comment has been removed by the author.

  16. Hi! Great post!

    I would like to build an UV detector, so I need to block any wavelenght below 250nm and above 400nm. Do you know any plastic or several of them together that can suit that filtering? Thanks!

    Kind regards

    1. Tough one. Maybe a specific color that matches those wavelengths?

    2. I'm also looking for UV-bandpass plexiglass which blocks all light above 400 nm but passes all UV from 254nm to 365 ~375 nm. something like the black IR-pass plexiglass but than instead for the UV frequencies. This is available in fused quartz (hoya U325C) but very expensive

  17. Thank you for the great information. Hoping you might be able to help me out with your knowledge on this subject. I have some Polycarbonate lenses that are range from about 1/4 inch to 1/2 inch thick. They have markings (small etchings) on the top of the lens that I want to be able to read with a camera. I'm thinking of using many IR LEDs to either backlight (or light from the top) the lens with hope the camera can see the etchings. Do you feel that IR will work for this on the Polycarbonate lens? Also what wavelength (nm) of IR LEDs would work best for this thickness of Poly? I was thinking around 1000nm. Thank you very much!

    Kindest Regards

    1. Depends on the camera sensitivity I would imagine. Sounds like a plan but you have to test first.....

  18. Hi Plastic Genius, I was wondering if you have infromation on the effect/ degradation rate of uvc light on acrylic? Thanks

    1. We are familiar with the effects of UVA and UVB, however not UVC. There have been no reports to us of UVC light being an issue with any UV-blocking acrylic application during our last 101 years in business. If more information is critical to your project, we recommend you call in and we will find the answers for you. 1-800-474-3688.

  19. Hi,

    The very last chart shows IR transmission through a polycarbonate sheet. Can you please provide more info as to which sheet this statistic is about?


  20. Fascinating stuff.
    I'm designing a new product using molded polycarbonate components. We inspect the parts after annealing using a modified polariscope to check of abnormal stresses and other defects. Works very well for the translucent parts but, in order to maintainthe same look & feel of the original product we want to keep the opaque base black. Considered just making the black just a little more transparent but still looks black and use a stronger light source.
    Might try IR illumination instead.