shield for metal halide lamp

[jkhudson]

I don't like the idea of a bare halide bulb above my tank. What can I use for a shield? Is acrylic or glass better?

 

[30mini]

glass...acrylic may melt with the heat

 

[Siklid]

i would not use glass, if it gets to hot it can shatter if water drops hit it, i use acrylic 2" away from my 250 watt mh's and sure it dips a little in the middle, but i dont have to worry about glass shattering into my tank, and if i realy want/need to i can replace the acrylic easy

 

[spitefull]

jk i seem to recall something about optical quality for shields not sure if thats for harmfull spectrum or light diffusion , double ended halides use glass shields and havent heard about them exploding,hopefully someone will chime in that knows

 

[CoolUsername]

There isn't a harmful spectrum for the fish/corals. The main concern for metal halides is UV emission. The outer glass on the MH is a partially for a UV shield, but doesn't provide full UV protection. Some MFR's add a uv glass to metal halide enclosures, but that is for your protection. The sun emits UV rays as well and fish corals live safely under this their entire lives.

I don't know the quantities of the UV rays emitted by MH bulbs compared to the sun. I feel though that given that they are close. there isn't enough exposure to the light for me to worry about it. I do however use acrylic shields, but mostly for better bulb airflow, since I have some very special venting requirements.

Hope this helps.

 

[jdieck]

I used to use acrylic but when I upgraded to 400 watters (from 175 watts) it melted. I switched to tempered glass which is what most good commercial hoods use.
Take your measurments and go to a glass shop, they will have them cut and tempered for you. It might take about a week to get it after ordered.
My hood is 72" long by 12" wide so I used three pieces to make it more maneagable. Each piece 24" x 12 cost me about $30.00

 

[johntbyrne]

FWIW, I work in a commercial HID fixture plant. We use several things for lens. In a pendant the lens can be either glass or injection molded plastics given the lens is not real close to the lamp. For all applications where the bulb is close we use glass. We do not have a single HID fixture I am aware of that uses acrylic or polycarb (lexan).