drilling my tank

I thought I had explained this before.
Just putting a phone/camera/laptop screen in front of tempered glass will not do anything. The LCD screens have a polarized filter on them. This means the light coming from them is polarized. Regular glass will just transmit this polarized light right through and the light will still be polarized. Tempered glass will 'scramble' the polarized light, so that it is no longer polarized. The only way you can tell is if you put a piece of polarized glass, like in a pair of sunglasses, on the other side of the glass from the light source. If the light is still polarized, meaning you can turn the lens and black out the source, then the glass is NOT tempered because it is transmitting the light without modificiation. If you can turn the lens and the light does not get blocked no matter what you do, that means the glass IS tempered, because it has de-polarized the light source.
I don't know what that other thread was trying to show with the laptop screen because the angle of the polarized filter means nothing, and beisides the picture didn't show what it said it did, it was just weird. (I just read it again and he is taking the picture through the sunglasses lens, which is why it is blocked out.  The funny pattern shows up when looking at the laptop screen through a polarized lens - if you look at that picture, you can see his reflection and he's holding the filter in front of the camera)
Also ignore the 'rainbows' part of the youtube vid I posted, that only works if you have a piece of tempered glass with a notch and was just showing another effect.

 

http://jolietareareefclub.com/forums/showthread.php?t=4509

http://www.youtube.com/watch?v=Yb9K3IGXwC0&feature=youtu.be

In both instances, you need a polarizing filter. If you read the first post on the joliet reef club he says just put sunglasses on, look at the screen/light source (no tank) and verify that the sunglasses are polarized by tilting your head or the light source and block it out. Then you put the glass in question inbetween you with the sunglasses on and the light source and do the same thing. If you cannot get the light to black out, the glass is tempered.