I went to a local glass store today to order a tempered glass.
The guy asked me what it was for, i said to block the heat from a 400w bulb. He said that tempered glass is heat proof but will not block the heat from passing on to the other side.

I'm not sure what to do. What do you guys think?

Thanks.

It will not block all the heat from going throught the glass but it will block about 70 percent

No the tempered glass won't block alot of the heat from the lamp. But that's why you have air flowing between it and the lcd.

trust me it blocks alot more heat than the standard lexan everyone uses here for sure.

Thank you guys for the input. I will order my glass next week.

dont forget to tell them not to put a "bug" on it, it needs to have no markings. you also want to pick up a UV filter from LL.

so is glass better than lexan?

I have Glass in PJ1 and Lexan in PJ2. I have to report that PJ1 runs cooler than PJ2. about 7 degrees cooler.

Would there be any benefit to using temp. glass And a thin UV shield togeather? Or is the lumen loss not worth it?
How important is the UV blocking properties of lexan ? How do I decide between the two(lexan vs Temp.) In terms of my intended use? Is it only a function of life of LCD / average use over time ?

Lexan is easier to use, it's easy to cut and it has the UV in it already. Tempered glass has to be custom cut. when using tempered glass you should get the UV filter to keep the LCD from fadeing over time from the bulb emitting the UV rays.

Another LL member gave a great suggestion for cheap tempered glass. A broken flatbed scanner from a computer surplus store. The glass is tempered and does not have a "bug".

In my standard PJ, the tempered glass blocks most of the IR. Then Lexan X10 is on the rear fresnel frame providing UV protection. My rationale is the LCD protection is worth the light reduction. After hours of operation, temperature at the LCD has never gone above 86F (30C).

ok as i understand the tempered glass blocks more heat than lexan does.tempered glass=better. But why to use a tempered glass when hot mirror is available(as i have read)? hot mirror blocks IR and has high transmitance 94%. is hot mirror much more expensive? which is the light transmitance of the tempered glass? is tempered glass more transmitive than IR glass? where can someone buy a hot mirror? is there any side-effects(ex.color) when using a hot mirror?

Hot mirrors bigger than 2"x2" are expensive, 2"x2" forces out to pit it very close to bulb and all that heat can cause cracks or coating overheating and breakdown (i.e. stops being hot mirror and becomes plain old glass. If Brainchild can get a decent size at a good price everyone should swicth. Problem is that there isn't a large need for hot mirrors, volume = low cost, no volume = high cost. Hot mirrors also loose more of the light as IR is pretty close to the red that we want to keep so expect a dimmer projection, not a show stopper but expect to lose 5-10%.

The hot mirror is not designed to replace the tempered glass, together they can reduce the temp at the panel. the hot mirror is designed to work with a specific bulb. I believe the hot mirror is made of Pyrex which will prevent it from cracking and turning into "plain glass". much research has gone into this mirror to give it the high quality and performance we have come to expect from LL products.

The Hot mirror would replace the tempered glass as it could both stop the hot air from hitting the LCD as well as reflecting the IR. The pyrex can withstand the heat but the IR reflective coating can have degraded performance if exposed to too much heat, "plain glass" was a poor example. But the Hot Mirror characteristics can be lost if the coatings get too hot.

bevo77 said: My rationale is the LCD protection is worth the light reduction. After hours of operation, temperature at the LCD has never gone above 86F (30C).

bevo77 how many fans u use? what type and what specs(cfm)?

Also when u have a tempered glass in the projector and LL uv filter how much air have to be moved with the fans? i mean how much cfm.Do i need a fan that pruduces more cfm than 110(i dont mean the evercool pcac.)?
if the new lamp has higher temperature at 400w then what? bigger fan needed? or we have to put lexan and tempered glass too(like bevo77 did)?
i will try a folded design.

Well.....My cooling setup was not scientifically-derived AT ALL. A combination of intuition and trial & error governed by my inherent cheapness. At the surplus computer store, I got the tempered glass from a broken scanner and 4, 80mm 120V fans -- all for $10.00. No specs were listed on the fans, I just plugged them in to see how much noise the made and how much air they moved. I put 3 of the fans in my PJ (the spacing was nice) and one in my separate "power brick" that houses the heavy coil ballast. The ballast is 15 ft away in a closet connected to the 'much lighter' PJ enclosure by #12, rubber-coated, 4 conductor power cable.

The airflow for the PJ is: from the bottom up the LCD panel (idea from Benchun), back down the rear fresnel, then under the tempered glass, and then across the face of the bulb and out the back panel where the 3 fans are mounted at the top. I put a simple dimmer control on the fans to adjust the fans' speed down as low possible while still staying in the safe range. The sensor of the $11 outdoor thermometer is mounted at the top of the rear fresnel.

A full day of running the PJ and watching the temperature proved that my initial set-up is OK. Could I have gotten by with just two fans or even one? Maybe, but that's for the next PJ project.

Thanks for your help bevo77. I asked about the fans because i am in dilema which fan to use. i am between two. the first is 120x38mm, 110 cfm, 37 db, 230v and the other is 172x150x51 235 cfm, 46db, 230v. the first costs 13.50$ and the second 38.00$. +12$ to be sent to me.But i think i will get the second seems to be better.i will use a dimmer too.these two are orion brand being sold at mouser.Also i will start searching the computer stores for broken scaners to take the tempered glass hehe