I MUST start this by saying that I have never used tempered glass in my projector, have not and do not plan to use LX10, and have not installed my hot mirror yet. In fact; I'm not using any heat sheild right now, and the LCD in my projector is working just fine, I even ran it for about 12 hours straight a couple weeks ago without any heat issues. On top of that, I have a very hot bulb (an 575w HMI) that not only has more energy running through it, I'm told that it also isn't as efficient as the other bulbs used by LLers, so a higher percentage of that energy is converted to heat. I do have a precondenser in there, but I think it could be argued that a precondenser would amplify the amount of heat radiated toward the LCD rather than reduce the amount.

I know a lot of people are under the impression that tempered glass will block IR light. I do not think this is supported by the facts. I bet the amount of IR that is blocked by the glass has more to do with the makeup of the glass than the tempering process. To put it a different way, if you take glass that doesn't block any IR and then have it tempered, I bet it still wont block any IR.

Then there is the idea that any glass will block UV light. Again, I don't think this is supported by the facts. I don't think this is a very commenly held opinion any more on this forum though.

So, what's the point of using tempered glass then? Well, it does stop heat from the bulb from being conducted. That is, it stops air that has been heated by the bulb from blowing over to the LCD, thus heating it. The thing is, adequate cooling can do a better job of keeping hot air away from the LCD, and it wont block any vital visable light. Lexan would do a perfectly good job here too.

What else is out there? A lot of people use a special kind of Lexan called "LX10" (I think). I'd say the biggest advantage of LX10 is that it's more transparrent than most glass at about 95% transmission (5%+ more than most tempered glass). A nice bonus is that it also blocks UV light (this feature has questionable "real world" benifit, but it's nice for the piece of mind). It is readily available (aparrently Home Depot and Lowes sell it). It's pretty darn cheap (I've heard it's around $10 - $15 for a piece the size we'd need). And it's easier to work with (it can be cut with a utility knife, unlike tempered glass which cannot be cut with normal means).

But, if you were to ask me (which I know you didn't...) I'd say the way to go is to use a Roxco "Hot Mirror". They block all the IR and UV light that hits em' and they look very transparrent (I couldn't tell the difference when I put the mirror in front of the triplet of my projector). The big problem with these is that they're expensive, at about $60 for a decient size piece (5-1/4" round from B & H Photo Video). BUT, you get all the piece of mind that you're blocking all the UV from your eyes/LCD and all the IR from the LCD. If mounted right, it could also provide just as much of a air sheild as the other options, but as I said; a good cooling setup will provide all the air control you'll need.

I wish I could provide some refrences, but for the few things I looked for I couldn't find...

Thanks Hiruden - I second all of your advice. I also don't think the tempered glass does much for people, except perhaps hold the fresnel straight and flat on one side. I'm sure it provides a little bit of benefit, but not a lot...

Your hot mirror suggestion is a good one. But the LCD is still going to heat up due to absorbing approx. 95% of all the visible light and whatever IR or UV comes its way.

That's where the cooling system comes in, by pulling lower temp. air across the LCD surface the heat will transfer into the air and be continuously pulled away.

Well, not ALL but one heck of a lot!!! If you got the cash a hot mirror IS a great investment without question.

So, I third your advice.

Using the Lexan might be a good idea for the HMI type of lamps for the extra UV protection. The amount of UV that a HMI makes is quite large.

Most people say that there is a UV block on the LCD but which side? If your LCD is backwards like mine (any non folded setup) that should place the UV block on the front so it will not protect the color filters or the polarizer. Then some people strip all kinds of layers from the LCD, too one might be the UV cut.

The two shell lamps with UV cut should not need the extra protection.

There is some condenser lens that boast both UV block and heat blocking.

Are we attempting to protect the LCD from UV rays; or are we trying to protect ourselves?

I think we're trying to protect the ozone layer to prevent global warming.

I don't use a heat shield but I do use a UV filter. I got it the LL store but can't seem to find the item listed there anymore... anybody know what happen to it?

Not stocked any longer. They're available elsewhere I've read here and there in the forums but ain't gone looking on my own as of yet. Happy Googling x!

I tried mine without a lexan heat shield and almost melted the LCD. It started turning black in the center. I have two 120mm fans rated at 110cfm. I must admit though that I am using a halogen lamp from an overhead. It might be ok for metal halide.

Global warming is a theory...

Oh geez. Let's not go THERE again.

Not much if any. I have measured my LCD temp at 32°, 2° lower than on its original backlight. The hot mirror is the only heat/uv protection in my PJ. I don't even have a dedicated cooling path, just fans underneath the LCD sled taking in air from under the PJ.