scholesy Posted February 15, 2006 Report Share Posted February 15, 2006 After some opinions from people out there with d/ended MHs, that aren't in fancy fixtures - i.e. they've mounted them in a hood themselves. Of course, DEs unshielded can apparently cook certain things in the tank, despite corals etc being exposed to UV in their day-to-day lives. I'm getting some heat-resistant glass to mount about 5cm below the bulb. The rectangle of glass will extend about 5cm from the bulb on all edges (about 15 x 25 cm). Apparently the glass'main benefit is the heat resistance - 165 deg apparently. Now I don't know how much if any UV is going to be blocked by it. I'm debating whether to get a piece of specialist UV (95% reduction) glass and mount it a few cm under the heat resistant glass. This piece of glass would be a bit bigger than the heat glass - say 20 x 30 cm - but it wouldn't encapsulate the bulb and some UV could still get out / bounce around the light shade. Questions: 1. Is the heat glass enough to stop the majority of UV? 2. Is 5cm a good distance away from the bulb? 3. Is the 2nd piece of glass necessary? 4. Is say 3cm for the UV glass from the heat glass ok? (too close / far) 5. Is the fact that the UV glass doesn't completely seal in the bulb going to be a problem? (the ends of the light hood will be sealed) Opinions, advice, theories... all considered with appreciation. Quote Link to comment Share on other sites More sharing options...
ghostface Posted February 15, 2006 Report Share Posted February 15, 2006 any glass 5mm+ thick should be fine, this will block most of the bad UV. the second piece isnt really necessary. check out the design of some halide pendants of the same wattage, these should be a good gauge of what is "safe" - thickness, distances etc. it would pay not to let any of the unfiltered light out of the reflector - whether it be into the tank, room or your eyes. theres a recent thread on this site where a guy had to have some medical attention due to "arc eye" resulting from an unshielded DE halide. Quote Link to comment Share on other sites More sharing options...
scholesy Posted February 16, 2006 Author Report Share Posted February 16, 2006 shielding my eyes will be fine - the hood is closed on the sides, top, and ends. I guess my best bet is to make the glass fit as well as possible within the hood to ensure minimum leakage into the tank. Maybe people out there could post the distance their UV glass is located from their bulbs? Last thing I want is shattered UV but not heat-proof glass filling the tank. cheers Quote Link to comment Share on other sites More sharing options...
ghostface Posted February 16, 2006 Report Share Posted February 16, 2006 mine are about 4.5cm bulb - glass. Quote Link to comment Share on other sites More sharing options...
reef Posted February 16, 2006 Report Share Posted February 16, 2006 DEs unshielded can apparently cook certain things in the tank, despite corals etc being exposed to UV in their day-to-day lives If you use de bulbs without a glass shield they will fry anything. Here is some info http://www.fnzas.org.nz/fishroom/1-vt11294.html?postdays=0&postorder=asc&start=0 Quote Link to comment Share on other sites More sharing options...
Ira Posted February 16, 2006 Report Share Posted February 16, 2006 All the UV-C that the bulbs give off would have been absorbed far up in the ozone layer. It's just a bit of UV-A and UV-B that reaches the surface and they're relatively harmless. Quote Link to comment Share on other sites More sharing options...
scholesy Posted February 16, 2006 Author Report Share Posted February 16, 2006 After much toing, froing, wailing, gnashing of teeth, and generally not getting anywhere.... I've decided that each bulb will have a boro-silicate heat resistant glass shield mounted approx 5cm from the bulb, extending approx 5cm from the bulb at the ends, and approx 7cm from the bulb out the sides. A little UV may still escape between the extremes of the glass and the inside of the light shade, but nothing's perfect. thanks for your thoughts everyone, appreciated. Quote Link to comment Share on other sites More sharing options...
scholesy Posted February 19, 2006 Author Report Share Posted February 19, 2006 Did some temp measuring out of interest, thought I'd post the results if anyone else was interested. 5cm below bulb: 70 deg C 5cm under bulb end-fitting: 55 5cm out from that: 40 9cm below bulb: 60 deg C 5cm down, and 4cm to one side of bulb: 67 Whichever way you look at it: they're hot! Anyone know what's the max temp ordinary glass can handle? Quote Link to comment Share on other sites More sharing options...
Alan Posted February 19, 2006 Report Share Posted February 19, 2006 You can cook it, but watch out when a drop of water hits it. Alan 104 Quote Link to comment Share on other sites More sharing options...
scholesy Posted February 20, 2006 Author Report Share Posted February 20, 2006 Looking at about $55 per 22x26cm piece but should be enough to block the heat nicely, and catch UV from the sides and one end of the bulb. Not cheap these tanks Quote Link to comment Share on other sites More sharing options...
Alan Posted February 20, 2006 Report Share Posted February 20, 2006 Why noy go to the recyclers. You'll get purpose made glass, able to withstand more extreme temps than your lights can ever hope to get to. I'm talking about the glass in a stove door or in a Kent-fire or similar. Cost?? Give the guy a couple of bottles of ale, the small ones. Alan 104 Quote Link to comment Share on other sites More sharing options...
suphew Posted February 20, 2006 Report Share Posted February 20, 2006 Might be worth a look, but they are often tinted plus you can't cut the glass so would only work if was the right size already. Quote Link to comment Share on other sites More sharing options...
scholesy Posted February 22, 2006 Author Report Share Posted February 22, 2006 I wondered about that but then thought about how I want them to fit as close as possible to my light hood. Still wondering about the UV light that manages to bounce around inside the hood and get out though. Hard to guess how much it will be.... Quote Link to comment Share on other sites More sharing options...
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