[prokinetic]

Originally Posted by Sawyer

I agree, 100%. Few appreciate that Indian cars are allowed to be registered with OE glass of VLT of as low as 70% and most Indian cars already have glass with tints that have VLT approaching those levels. Almost no car has glass with 100% VLT.

Of course heat rejection and UV reduction isn't just a matter of tinting...

My car has 'Transparency 70%' written on all the glasses including quarter glasses. Does that mean they're tinted? If yes, then do they provide some protection against UV?

There are umpteen solutions for windows. My main concern is windshield. If at all I decide to go for front windshield film on such a glass, would I end up darkening my vision further which could be problematic during night drives, which in turn could make me want to upgrade to powerful headlamp bulbs!

[Sawyer]

Yes, it means they are tinted, but all tints do not automatically counter UV, so I can't speak to that in your car.
And yes, any illegal addition would darken things further, depending on how much the addition is tinted. Mere upgrading headlamp bulbs would not reduce the risk of not adequately seeing things outside and in time - things that are not in the direct beam of the headlights.

[Thad E Ginathom]

My VW Polo has tinted glass, but something puzzles me: my wife's photochromic glasses darken inside the car. Does that mean that the car glass is not stopping UV?

Her lenses are nothing very fancy. Maybe "Transitions," or the equivalent sold by that optical shop, which was a fairly low-cost place.

I am still very tempted to fit CR90, for a little extra heat and glare exclusion. First, I have to find a dealer, though, as when I last looked, 3m only go to CR70, and then I have to decide that I am willing to run the risk with the legal situation. So, for now, it remains just a temptation.

[Sawyer]

That is strange considering that I have found that my photo prescription glasses don't go anywhere as dark inside the car as they do out of doors because there they react to UV falling on them.

But see: "Also, since they are activated by UV exposure, most Transitions lenses don't work behind the windshield of a car (your windshield actually blocks UV rays). However, Transitions® XTRActive® lenses do activate moderately behind a windshield as they react to both UV and visible light."

I have CR90 on my front glass and by spec it does a lot less heat rejection than 70 or lower, although UV and glare reduction is still good. But if the OE glass does UV rejection already to the same extent, it will be an unnecessary expense. If you park in the sun, you will be better served by installing the shiny reflective shades that are available for the windshield, which will do a better job.

[caffeineAM]

I am going to end up bumping this old thread, but I recently came across a YouTube video where the presenter (a physician) does analysis of his and his colleague's cases. One of which was about a farmer who ended up with cancer because of his time spent outdoors without any sun protection.

Although most people here probably don't spend as much time in the sun, given that radiation cutting films are banned, please do take necessary precaution.

Link:

https://youtu.be/KKaJhQBusH8

[Rathore_13]

Originally Posted by caffeineAM

I am going to end up bumping this old thread, but I recently came across a YouTube video where the presenter (a physician) does analysis of his and his colleague's cases. One of which was about a farmer who ended up with cancer because of his time spent outdoors without any sun protection.

Although most people here probably don't spend as much time in the sun, given that radiation cutting films are banned, please do take necessary precaution.

Is there someone picking this battle up and fighting for this very basic right? i.e. The right to tint your car whatever color and transparency you want. Shouldn't this be a fundamental right?

[Thad E Ginathom]

If the question is black and white, the answer is no! Why? Because stuff that makes a car more dangerous certainly should not be a fundamental right.

If the question is shades of grey, then perhaps so. I support the right to make a car more comfortable, which can make it safer. If the courts reexamined this ruling, perhaps they might find a way to give a ruling in shades of grey. But nobody is doing anything about that. I'm still surprised that manufacturers just keep quiet.

[caffeineAM]

Calling it a fundamental right is a bit much in my opinion. The judgement was too broad and it has not really been challenged. I doubt anyone will challenge it since alternatives like sun shades are available despite being cumbersome to use.

I personally, will keep trying to sneak under the radar with light films because they make the car more comfortable, reduce the load on the engine and hopefully reduce fuel consumption and therefore reduce the country's import bill (I'm fishing for excuses here).

[sgiitk]

Originally Posted by Thad E Ginathom

My VW Polo has tinted glass, but something puzzles me: my wife's photochromic glasses darken inside the car. Does that mean that the car glass is not stopping UV?

Her lenses are nothing very fancy. Maybe "Transitions," or the equivalent sold by that optical shop, which was a fairly low-cost place.

It is very likely that the windscreen does not cover all the wavelengths which re covered by the glasses. Even otherwise the 'tinted' glass is not 100% so some light does get through. As has been pointed out photochromics do not get as dark in cars with tinged glasses.

[Motard_Blr]

Originally Posted by sgiitk

It is very likely that the windscreen does not cover all the wavelengths which re covered by the glasses. Even otherwise the 'tinted' glass is not 100% so some light does get through. As has been pointed out photochromics do not get as dark in cars with tinged glasses.

Photochromic lenses are usually sensitive to UV, not visible light. Most windscreen glasses these days do block some UV light hence the decreased response of photochromic lenses.

[gostel]

I am writing this once again. 1.) The ordinary untinted glass is inherently opaque to UV, so where is the need for adding any gimmicks for UV? 2.) Visible light bears no heat hence reducing it does not actually reduce heat. 3.) The infra-red region of sunlight bears heat and the only way to reduce its effect is to reflect it away from the OUTER surface of the glass window. Sun-films are banned and tinting does not reflect infra-red from the outer surface hence it is just a gimmick. But then, why do you feel more comfortable using the sun-film? The comfort we feel is just a psychological feeling when the total light falling directly on our face is reduced.
We see people walking in the hot sun without sun films. They don't use sun films but use caps, hats, face-covers, nettings, etc to reduce the direct radiation falling on their faces. There is a lot of money to be made selling sun films and a little misinformation helps. No offence to anyone is intended.

[n.devdath]

Originally Posted by gostel

3.) The infra-red region of sunlight bears heat and the only way to reduce its effect is to reflect it away from the OUTER surface of the glass window.

So a sunfilm, which provides a more reflective surface to the glass due to its increased opacity will reflect/deflect more of this IR sunlight away from the window, right?

[Thad E Ginathom]

Originally Posted by gostel

I am writing this once again. 1.) The ordinary untinted glass is inherently opaque to UV, so where is the need for adding any gimmicks for UV? 2.) Visible light bears no heat hence reducing it does not actually reduce heat. 3.) The infra-red region of sunlight bears heat and the only way to reduce its effect is to reflect it away from the OUTER surface of the glass window. Sun-films are banned and tinting does not reflect infra-red from the outer surface hence it is just a gimmick. But then, why do you feel more comfortable using the sun-film? The comfort we feel is just a psychological feeling when the total light falling directly on our face is reduced.

What about the physical discomfort of high brightness? I don't think that is psychological.

We see people walking in the hot sun without sun films. They don't use sun films but use caps, hats, face-covers, nettings, etc to reduce the direct radiation falling on their faces. There is a lot of money to be made selling sun films and a little misinformation helps. No offence to anyone is intended.

I think you left out sunglasses, which are a great aid to walking in the brightest sun, for the same reasons that films increase eye comfort when driving. Oh, sure: we could wear sunglasses when driving.

The sunfilm companies publish specifications. If I could get a totally clear sunfilm with high heat reduction, I'd buy in a flash. Is the company information false? I do not know the science/technology of tint related to heat reduction. It's been a while since I even looked, but, if I remember rightly, taking the locally-available 3M products, CR70 blocks (or is claimed to block) substantially more heat than the lighter-tint CR90, but the CR90 is also more expensive. So why would they not give us the same heat reduction in that product if they could? Is such a product available elsewhere? It is on my wish-it-existed list, so I'd be happy if you can tell me that it does or could.

Please don't worry about offence: if something is a fact, it's a fact. Let anybody who gets offended at facts worry about it. But do please be prepared to back up your facts, and/or give further information.

I have no film on my current car, although there is a slight manufacture tint. My previous car had CR70. It was certainly cooler as well as more comfortable to drive. And cooler than my current car. Comparing the two cars fairly, though, is difficult, as the current car is black --- not the best of colours in the tropical sun!

[gostel]

Originally Posted by n.devdath

So a sunfilm, which provides a more reflective surface to the glass due to its increased opacity will reflect/deflect more of this IR sunlight away from the window, right?

Right? I don't know if that is right. It is your assertion, not mine. The manufacturers have not made any claims about 'reflection', they only specify 'transmission' so please figure it out for yourself. But thanks for your reaction to my reply on this thread.

Originally Posted by Thad E Ginathom

What about the physical discomfort of high brightness? I don't think that is psychological.
I think you left out sunglasses, which are a great aid to walking in the brightest sun, for the same reasons that films increase eye comfort when driving. Oh, sure: we could wear sunglasses when driving.

The sunfilm companies publish specifications. If I could get a totally clear sunfilm with high heat reduction, I'd buy in a flash. Is the company information false? I do not know the science/technology of tint related to heat reduction. It's been a while since I even looked, but, if I remember rightly, taking the locally-available 3M products, CR70 blocks (or is claimed to block) substantially more heat than the lighter-tint CR90, but the CR90 is also more expensive. So why would they not give us the same heat reduction in that product if they could? Is such a product available elsewhere? It is on my wish-it-existed list, so I'd be happy if you can tell me that it does or could.

Please don't worry about offence: if something is a fact, it's a fact. Let anybody who gets offended at facts worry about it. But do please be prepared to back up your facts, and/or give further information.

I have no film on my current car, although there is a slight manufacture tint. My previous car had CR70. It was certainly cooler as well as more comfortable to drive. And cooler than my current car. Comparing the two cars fairly, though, is difficult, as the current car is black --- not the best of colours in the tropical sun!

Thanks for your reaction to my reply on this thread. Let me try to respond to your queries as best as I can. I have already stated 3 facts in my reply but you do not believe what I have written. You could consult a friend close to you who knows his physics well. He will confirm the facts I have stated. In our lab, we had to use special quartz cuvettes for UV spectrum studies because the ordinary glass was opaque to UV. Quartz cuvettes were terribly expensive. As an aside, many of the perspex sheets are transparent to UV. Coming to sunglasses, use polarizer type sunglasses and avoid the cheap tinted ones that only fool you and could damage your eyes over long exposures. I would encourage you to NOT make emotional judgements but be objective in your approach. I am a retired scientist and learnt the hard way to avoid emotional judging. Sorry, I can't teach you that from a distance but believe me, we used to have sessions where we would shoot down each other's emotional judgements as an exercise. Your old car may have had CR-70 but then there were many other differences like volume, AC power, size of windows, and the car itself. As an experimenter, I am allowed to make 'strictly' a single change to observe a difference.
Now coming to the concept of a clear film that reduces heat transmission. If the manufacturer claims reflection then I challenge him to prove it to me, haha. If the film absorbs the heat then it is no good because it is stuck to the glass and it transmits the heat to the glass by conduction.
Here is a little trick I learnt from a Youtube post. When you start your car that has been standing in the hot sun, here is what you can try. Partially open your windows and start the car and then AC and keep the air-flow to the 'Feet-only' configuration. The cooled air will start from the bottom rising up driving the warm air out of the partially open windows and cool your car faster and more efficiently while you are stepped out for a couple of minutes. Now get in and change the air-flow to normal and you are good to go.
There is a second neat trick that comes before the above trick. Before you get into that 'hot' car, open the window of the co-passenger and swing the driver's door open-and-shut a few times to pump out the hot air from the car through the open window and substantially reduces the heat in the car. After this get into the car and do the above little trick. Hope this helps.

[Thad E Ginathom]

I don't know where you find my reply to be emotional! Perhaps you didn't read it very scientifically.

I didn't make it clear that the two cars in my comparison were the same make and model. Have you compared two such cars? Looks to me like I was being quite scientific.

If you simply appeal to me to believe in your facts, then it looks like your argument is more faith-based than scientific. I am not very keen on faith. I asked for clarification. You could have enlarged usefully on your points. I laughed at the the last person who told me "Trust me I'm a doctor." (True story. Actually, I thought he was joking; it only occurred to me later that he hadn't been. Mind you, I was there to let him get on with his job, and I did, so you could say that I trusted him anyhow.)

Yes, your ideas on how to cool down a hot car are all good. Been part of my repertoire for quite a while. I'm an experimenter, you see!