Shaun, Greenhouse glass is the only kind that UVB can pass thru, so you'll have to find another way to hang up your tube. I bought some suction cup thingies and hung my tube inside the aquariums for both my Uromastyx and my Spiny-tail. Good Luck.
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I find it intriguing to hear you say that UVB is highly diminished when it goes through screening. It makes sense, but it opens up some interesting questions. Just how diminished is it? And since its now recommended that UV bulbs be no less than 8 inches from your iguana, how would you keep them from getting burned without some sort of barrier ( i.e. screen)?
Flourescent tubes dont put out the heat like a regular incadescent bulb...so they should be safe as long as they are not leaning directly against the bulb for any amount of time...with the mercury vapor bulbs of course you have to be extremely careful of temps but they can be up to 18 inches away....Lyn
Hey Merlin. I'm not sure what you mean by 'fine mesh', but I use window screening for the barrier between my iguana and the fixture. I guess I'm going to have to come up with something different, eh? He seems to so fine with the set-up now, but I guess I need to be on the safe side.
The standard run of the mill window screen is what I was talking about. Tests have shown that it shades out a good portion of the usable light. Any hard ware store can fix you up with 1/4 inch hardware cloth (a type of screen). All you need to do with a flourescent fixture is to make a tube of it so the ig can't break the bulb. The flourescents don't get hot enough to be a burn problem. Just remember to make it so you have easy acess when you have to change out the bulbs
To give you an idea of how much the screen cuts down on the UVB emission, I just went outside after reading this thread to see how much the difference is.
At 4:30 pm in the W TN sky: Direct sun: 110 uW/cm2 Through window screen: 58 uW/cm2
The UVB is nearly cut in half. The UVB tubes provide minimal UVB emissions as it is. When you add to that the reduction the window screen adds to the equation you get less than half of the original, usable UVB.