uv rays

[rwag]

I have come to realize that I should probably put something between my 3-250 metal halides and the water surface to block uv rays. Any recommendations as to what I should use/ where I should get it? Does most everyone on this board use something to filter the uv or not? TIA
Ryan

[hllywd]

I use a window glass strictly as a splash shield. I'm sure this causes some reduction in intensity and I would do without if I could.
Tim

[Ninong]

Here is an article by Dana Riddle that discusses this issue: http://www.aquarium-design.com/reef/uvlighting.html

[scubadude]

I have 3 250w HQI bulbs and am using a 1/4" tempered glass as a uv/splash shield

[turtlespd]

Rdawg,

Do you have DE or mogul base? if its DE you best get some 1/4 inch tempered glass...UV is no joke..bad for you and your corals..but its its mogual base...you dont really need it..water may spalsh on it but usually it will be ok unless you really get some water on it..i have mines about 7" above the water and i see small water spots on them all the itme..

I wouldnt use the glass if it were mogul..DE you best head out today and get someting..good luck


Paul

[rwag]

Turtlespd,
Mine are mogul sockets. i was concerned about water splashing up on them I wonder if they would explode? Wonder if anyone has had the unfortunate experience of that? THanks
Ryan

[Claude Pool]

To All:

Tempered glass is great as a shield but IT DOES NOT filter UV rays.

Claude Poole

[scubadude]

Originally posted by Claude Poole
To All:

Tempered glass is great as a shield but IT DOES NOT filter UV rays.

Claude Poole

I beg to differ

There are two ways that it filters transmission IMO

1. Regular soda glass (green glass) does not have 100% transmission there is an element (Iron i believe, but dont quote me) that makes this glass much stronger but at the sacrifice of transmission propertys.

2. Using it as a splash protection will acrue dust and salt buildup on the glass thus decreasing your transmission properties.

About the only way I could agree with your statement Claude is if you had a starphire glass shield, but that would comprimise the strength thus defeating one of the purposes you need for this shield "strength", tempered glass is needed for the strength from the heat that the bulbs will put off, and the thicker the glass the less light transmission you will have, thus the more UV protection you will have. I studied this topic immensely before I took on my DIY HQI canopy as I knew that I would be exposed to the lights quite often! The trick is finding the happy medium Let me ask you this Claude....what do you recommend as a UV shield?

[Claude Pool]

<<The trick is finding the happy medium Let me ask you this Claude....what do you recommend as a UV shield?>>

You're so right about finding a happy medium. For example:

You could use Schott Robax which is a ceramic glass. It blocks almost all UV and can handle 1400 degree F. Unfortunately it also reduces transmission in the wavelength we want most such as the blues by as much as 60%. Not a good choice unless you have a lot of PAR to waste.

I am personally considering Schott Borafloat, a borasilicate glass which blocks large amounts of UV, has high temp capablilities and allows good transmission of longer wavelengths such as the one we need.

Product info for the above, including optical data, is available from Cincinnati Gasket packing & Mfg, Inc. Phone 513-761-3458. They will fax it to you if you ask. Also some info is available on www.schottglass.com. It's been a while since I did the research, I don't remember what the website has to offer.

I also spoke with Dave at PFO. They use a UV blocking glass for their mini pendants and perhaps others I don't know about. They get their glass from a local manufacturer. I understand that it is not a coating however. Not being able to access optical data bothers me so I lean toward the Schott Borafloat.

Pyrex also has a UV blocking glass. They did not get back to me with the info I asked. After the tax season I will resume my search.

Claude

[scubadude]

But I believe Paul (LTSPD) called around and found out that Schott Borafloat is the same as regular soda glass, and if thats the case then Schott Borafloat=Regular tempered glass.

[Claude Pool]

Paul is probably refering to Schott DURAX which is a different animal = tempered glass. Does not block UV to any appreciable extent

Claude

[Rin]

Originally posted by rwag
Turtlespd,
Mine are mogul sockets. i was concerned about water splashing up on them I wonder if they would explode? Wonder if anyone has had the unfortunate experience of that? THanks
Ryan

Yes, I have. One of my wrasses made a leap and got the bulb. Luckily, the bulb broke into only 5 pieces.

As far as UV shielding goes. Wasn't there a recent post about soda glass blocking UV-C and UV-B rays well enough to permit its use in aquaria. I think Paul and Ninong debated it extensively...time to use the search function.

[Papa Doug]

My glass company agrees with Claude. Tempered does not block UV. Now how much does the things mentioned by Scuba block UV. I dont know, but I would have to agree with him, that a decent portion must be blocked.

I have tried Lexan tank covers, but they haze to quickly. I use a 3mm tempered glass shield on my 400w pendant and 5mm glass covers on my tank. I sometimes leave the tanks covers open. How much UV is this blocking. I dont know.

I have heard many say that the glass does block some UV, but without a meter, who knows.

[Rin]

Not really anything that says soda glass is OK, but it does go over a lot about HQIs vs Mogels and some references about the safety of corals and fish.

Here it is:

http://www.reefland.com/cgi-bin/foru...&threadid=4267

[turtlespd]

Rin,


Yes, I have. One of my wrasses made a leap and got the bulb. Luckily, the bulb broke into only 5 pieces.

but its its mogual base...you dont really need it..water may spalsh on it but usually it will be ok unless you really get some water on it..i have mines about 7" above the water and i see small water spots on them all the itme..

I did state that i had water sligtly splash on my bulbs..you had a wrasse...that a fish for got sakes...and i did mention only if you "really get some water" {wrasse} for example...

Paul

[bowfront]

I'm not sure why you both agree that glass doesn't filter UV. According to the Dana Riddle article linked to above by Ninong regular untempered glass filters 97% of UV-B and most likely 100% of UV-C. We went through this before in another couple of threads here a while back. I think a good quality tempered glass such as Schott Durex should work fine for most applications including HQI DE. Here's a table from that article listing the transmission properties of various materials. Don't forget UV-B and UV-C are the bad boys.

Transmission Properties (Percentage) of Various Materials Material

Thickness (Aprx.) PAR (%) UV-A (%) UV-B (%)

Lexan 1/8" 86 <1 <1
Lexan Solar 3/32" 89 <1 <1
"Green" Glass 3/16" 91 73 3
AtoHaus UF-3** 3/16" 90 5 <1
Unknown Plastic*** 3/16" 92 85 35

[Rin]

It's cool turtlespd.

My lights are 8" up. I was simply replying to rwag's question as to wether anyone has experienced an exploding bulb. I was just relating my experience. The wrasse is only 3"- 4" long.

I agree that small splashes are not likely to do any damage.

[Papa Doug]

My read, shows his tests say 73% of the UV"A", is passed through normal glass. Although the least destructive of the uv spectrum, some of his reference articles show its effect on some corals.
You are correct in that glass allows only 3% of UV"B" through, which is the most destructive.
Thats why the reference to glass in my post. I do use a tempered shield & glass covers. The non-filtering of UV by normal glass, is what the glass companys will tell you. Why??, if they filter some out. Perhaps because its not an overall UV filter??
I am picking up a new shield on Friday & will mention some of these figures to him and see their response.

Anyways, glass is my choice for now. My mine reason for mentioning the article in these posts,{and thats often}, is to show the tests on the UV blocking ability of metal halide envelopes.