# custom glass cover/lens question



## tsound (Aug 22, 2006)

i built a 70W HQI pendant using a security light fixture.
everything is perfect, except for the glass cover of the fixture is frosted.
i am sure the light would be much brighter with a clear glass cover.
what kind of place would cut a custom piece of glass? window store?
also, since it is a metal halide bulb, does it have to be a special uv-resistant glass?

thanks


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## blacksmith37 (Oct 10, 2006)

The primary function of glass is to prevent water from splashing onto the bulb and building deposits, or breaking the bulb, and reduces the heat put into the water.
I have a 400w metal halide about 6" above a 125 with no glass between. It is on for only 4Hr a day, no problem. I only use glass or plastic covers to reduce evaporation/reduce heat loss.


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## tsound (Aug 22, 2006)

what about the uv? isn't the uv output of a metal halide dangerous for plants and fish and bacteria?


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## hoppycalif (Apr 7, 2005)

All glass absorbs UV. That is both good and bad. Good because it reduces what reaches the water, and bad because it can make some glass become colored. I think I would use a glass cover on the light fixture, and if you take the frosted glass to almost any glass store, or even most hardware stores, they will cut a matching piece. Frosted glass scatters the light, increasing the amount that spills outside the tank. That is desirable for a security light, but not for an aquarium light.


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## tsound (Aug 22, 2006)

thanks hoppycalif,
so you think regular glass would do the trick?
or should i look for 'UV-glass', like Loe2-glass?


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## hoppycalif (Apr 7, 2005)

MH bulbs don't radiate a lot of UV, and very little if any in the really dangerous part of the UV spectrum. So I would just use ordinary glass and if that cracks or becomes too discolored after a few months I would then try for a better quality glass. Remember, a security light is normally out in the open where people can look directly at the light. The manufacturers of those lights would take great pains not to damage those people's eyes.


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