sdrawkcaB

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I thought perhaps some of you may be interested in some technical trivial data on the factory glass with regards to light transmittance of visible, infrared, and ultraviolet light.

I took these measurements of the front driver and passenger windows of a 2006 Honda Pilot. The glass was untinted, nor did it have any aftermarket window film applied. The glass on the vehicle is all OEM original with Honda's own logo screen printed onto it still, indicating that the glass was either 100% original as it came from the factor production line, or was replaced with an authentic OEM replacement provided by Honda.

I used a Linshang LS162 transmission meter to measure the visible light, ultraviolet light, and infrared light that is transmitted through the glass. Linshang states that the LS162 is accurate to within 2% tolerance at most. I did find that by moving the device around while positioned atop the edge of the glass, I was able to influence the readings slightly. By finding the flattest portion of the glass available, typically located at around the 1/2 way point from front to back of the glass, I observed readings to be more consistent and repeatable. I removed the tool from the glass and reset it to recalibrate it a few times, before placing it on the glass once more. I repeated this three or four times to confirm the results were consistent.

The 2003 to 2008 Honda Pilot Front Driver & Passenger Glass Light Transmittance Results:
The transmitted (light passing through) was rounded up to the nearest percent.
  • Visible Light Transmission (VLT): 80% (20% rejected)
  • Ultraviolet Light Transmission: 60% (40% rejected)
  • Infrared Light Transmission: 80% (20% rejected)

For those of you interested in understanding how the LS162 measurements are taken, the LS162 tool uses 3 diodes and 3 receivers which are aligned to each other respectively. These transmitter and receiver pairs are held in place by the chassis of the tool which is designed in a "U" shape. When the device is first powered up, the path between the transmitter and receiver diodes should be unobstructed. Calibration will result in it determining the unobstructed path to be considered 100% transmission across all wavelengths. Once calibration is completed, you can then begin testing your given material. The material being tested is then placed in between the transmitters and receivers, putting the material into the center of the "U" shape. In my case, this meant having my car windows rolled down part way, leaving ~8 inches up above the door line, then placing the device over the top of the glass with the transmitters and receivers on opposite sides of the glass. The device sends pulses of light across the sensors, and then reports the output.

The Linshang LS162 utilizes the following center wavelengths for the respective measurements:
  • Visible Light Peak wavelength: 550nm
  • Ultraviolet Peak wavelength: 365nm
  • Infrared Peak wavelength: 950nm
Thoughts:

I had always heard that factory glass blocks Ultraviolet light. I was surprised to find that even though more ultraviolet light was blocked than was visible light and infrared light, the factory glass still was passing a very high amount of ultraviolet light through. I would recommend getting an aftermarket window film. If you don't want to visually darken the film but would like to get the thermal benefits of blocking infrared and ultraviolet light, as well as have the medical safety benefit of reducing the risk of getting skin cancer, there are options available.

Non-tinted Aftermarket Films:
for those who may not want to visibly darken their windows, but still get the benefit of rejecting heat and skin damaging ultraviolet light
  • Llumar Air @ 90% or 80% VLT
  • 3M Crystalline @ 90% VLT
Tinted Aftermarket Films:
for those who don't mind visibly tinting or would like to have visibly tinted glass
  • Llumar Formula One Pinnacle: 50, 40, 35, 30, 25, 15, & 5% VLT
  • Llumar Formula One Stratos: 70, 50, 40, 35, 30, & 15% VLT
  • 3M Crystalline: 70, 60, 50, 40, & 20% VLT
I've attached a few product brochures obtained from both 3M and Llumar (Eastman Films). Be aware that some of the PDFs have specifications for multiple product lines in addition to the ones mentioned above.

Since doing this test, I have gotten my windows treated with window film (a.k.a. tinted). I am currently using a combination of products on my vehicles. I have 3M Crystalline 80% VLT for my sunroof. I have Llumar Formula One Pinnacle at 35% VLT for my front side windows. For my rear sides and rear windshield, I have Llumar Formula One Pinnacle @ 5% VLT. While the Stratos is a higher performing product than the Pinnacle, the cost increase for the material is about 2.5x more. The performance gains are minimal (~2 to 5%), so the Pinnacle tends to be the best value in the high end window film category, in my opinion.

All of the above named products are premier offerings, and only select dealers for the respective brands will be authorized to carry and install the materials. Both 3M and Llumar tightly control which tint shops are allowed to sell and install it, in order to maintain a high standard of installation and warranty standards. You'll want to use their websites to locate an authorized shop that can install these high end window films on your vehicle.
 

Attachments

  • Llumar_Air_Specs.pdf
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  • Llumar_Pinnacle_and_Stratos_performance_specs.pdf
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  • 3M_Crystalline_Specs.pdf
    6.3 MB · Views: 46

GTO_04

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I always wondered about the UV transmission. That is why we don't get sunburned while we are driving lol. Having said that, I am surprised that the glass lets even that much UV light through. If it lets enough UV-B light through we can still get some of our daily Vitamin D3.

GTO_04
 

Deacon

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Since doing this test, I have gotten my windows treated with window film (a.k.a. tinted).
Have you redone the test after tint? Both are trusted brands, but it would be neat to verify results.

Great stuff, by the way!
 

barry

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Great info @sdrawkcaB. Very nicely done.

You mentioned there was more UV transmission (about 60%) than you expected. I bet you would have measured much less UV transmission, probably below 2%, if you had been able to check the windshield glass. Of course, this measurement wouldn't be easy with the LS162. As I'm sure most folks on the forum already know, the windshield is laminated safety glass and has an internal polymer layer (glass-polymer-glass). The polymer will absorb almost all of the UV radiation. Of course, the polymer is there primarily to hold the windshield together in an accident and help prevent glass shards from going everywhere.

Side and rear glass is almost always not laminated but is highly tempered instead. When it breaks it forms many small, blocky pieces that aren't much of a cut hazard. Since there's no polymer layer, it transmits more UV. Normal soda-lime window glass will transmit about 90% of UV light with wavelength over 350nm, but only 10% or so of UV light with a wavelength below 300nm.

As you said above, with the proper film you can block most UV and IR without even appreciably darkening your windows.
 

Exadata

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Thanks for the post and great info!

3M Crystalline is my personal fav. It comes in 90, 70, 60, 50, 40, and 20%. Not sure about other brands but, the 90% is probably one of the best if you want your windshield tinted for blocking UV and going unnoticed.
 

wjbertrand

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Surprised to see that much UV getting through the glass at all. In chemical analysis we must use quartz cuvett sample cells to do any kind of UV spectrometer testing. Agree with the comments about the windscreen blocking almost all the UV due to the polymer layer. My own anecdotal experience is that my Transitions eyeglass lenses will not darken when I’m inside the car.


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poolmon

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On a 2-day road trip from DC to FL a few years back I got a sunburn on my face and arms while driving my car.
I was taking a temporary medication for something (I can't even recall what) but it increases sensitivity to UV light.
Not in a million years did I expect that much UV light to pass through those windows, especially since I was otherwise shaded by the vehicle. I looked like I had been sunning on the beach for those two days of driving.
 

MurrayB

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I have an autoimmune disease and do not have an outer layer of skin on my hands. I am in trouble, sunburn, if I don't wear gloves when I drive due to the UV.
 

Deacon

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I have an autoimmune disease and do not have an outer layer of skin on my hands. I am in trouble, sunburn, if I don't wear gloves when I drive due to the UV.
I take it even with >99% UV rejection, it would still be too much coming through?
 

wjbertrand

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If that’s the case, why are so many dashboards faded and cracked with age?

Being a polymer chemist, I can answer that!

Heat and visible light can degrade vinyl (PVC), you don’t have to have UV light. The main thing is heat that drives the plasticizer out of the material. It’s what leaves that film on the inside of the windscreen. The volatilized plasticizer condenses on other surfaces inside the car, most noticeably the windscreen. Pure, unplasticized PVC, is extremely brittle. Also, as the plasticizer is lost, the vinyl material will shrink, tightening it. Flexible vinyl materials contain significant proportion of plasticizer, 30-40% is common. Eventually the stress on the embrittled material causes cracking. You can see the evidence of the shrinkage because once cracked, the crack pulls wide open.


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The Pope

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I have the Llumar Formula One Pinnacle products on my car including Blue80 fully covering my windshield.


I know that this might be a little off topic... but.....

I acquired some Blue70 for LIDAR Testing with @VariableWave just to see how it could/would effect LIDAR.

Short answer... when holding a piece of the Blue70 in front of the LIDAR Gun, there was a slight difficulty of target acquisition by the gun. Also placing a piece of it over a easily read target on @Kennyc56 car, the LIDAR's ability to get a reading from that target was slightly reduced.
 

sdrawkcaB

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Have you redone the test after tint? Both are trusted brands, but it would be neat to verify results.

I think it's time I post some follow up data. I tested the front side windows after getting the film applied. The film was Llumar Formula One Pinnacle rated at 35% VLT. Here is what my LS162 metered it as when applied to my front side windows. There can be variance from vehicle to vehicle since not every glass window is exactly the same.
  • Visible Light Transmission (VLT): 33%
  • UltraViolet Rejection (UVR): 100%
  • Infrared Light Rejection (IRR): 96%
Llumar_Formula_One_Pinnacle_35_Percent.JPG


I bet you would have measured much less UV transmission, probably below 2%, if you had been able to check the windshield glass. Of course, this measurement wouldn't be easy with the LS162.

You're correct, the LS162 wouldn't be usable on an installed windshield, or even a free standing windshield if it had blackout or fritts around the edges, as most seem to have. I would like to actually get a different tester that comes with two separable parts, a transmitter and a receiver, so that I could test the windshield. If I can find one that does all three wavelengths and for a good enough price, I may grab one.
 

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