At what temp does glass break?

[skriz]

I want to lower my lights to get a little better penetration.

1/2 of the fixture overlaps the centerbrace (3/4" starphire glass). How close can I safely go with 400W Se bulbs?

At what temperature will the glass break? I can lower slowly and test the temp of the glass.

 

[tpdpercula]

From my experience DO NOT GET IT TO CLOSE! I don't know the breakage point but I lost my center glass brace on my 300 gallon because of just a 250 watt MH. I would not go any closer then 6-7" but thats my 2 cents.

 

[skriz]

whoa, that sucks! How close did you have your 250w?

 

[foodstamp]

its not so much the "temp" of the glass that shatters....its cooling it down once heated

its the cold water hitting the hot glass more then likely right after lights go off and its not cooled down yet

ever put a beer bottle in a campfire?
it get so hot u can form it to what ever shape u want. 90% of the time it dont cool down right and cracks