[Don_1 (OP)]

As you may be aware, I have a couple of tortoises. For their metabolism to work properly they require UV light. During the summer months, while they are out in natural sunlight, this is not a problem, but now that the summer has suddenly departed they are on their tortoise table with two 40W reflector spot lamps for their heat requirement and a 48" 5% UV tube for their UV requirement.

This UV tube has an effective range of around 12", so it is set on the ceiling of the covered section of the table. This is a box of 54" width x 18" depth x 15" high and is made from wood effect contiboard. Though the surface is shinny, I thought of covering the ceiling of the box with aluminium foil to reflect more of the light from the UV tube. Would the UV wavelength be reflected along with the visible light, or would the foil absorb the UV?

[imatfaal]

I believe Aluminium is highly reflective in the UV band.  Will dig out confirmation.

[imatfaal]

http://en.wikipedia.org/wiki/Ultraviolet_germicidal_irradiation - under effectiveness.  I am sure there is a better resource somewhere but I cannot find it

[yor_on]

"There are two common urban myths about fluorescent lighting and UV exposure. The first myth says that fluorescent lighting generates hazardous amounts of UV rays, rivaling direct outdoor sun exposure. The second one says that the first myth is complete nonsense and that fluorescent lighting generates no UV rays whatsoever.

The reality is a bit more complicated. Most fluorescent lamps work on the following principle. Inside the lamp, electrical discharge excites a gas (usually neon or mercury vapor in argon), which emits ultraviolet radiation. UV rays hit a special dye covering the bulb, which absorbs UV radiation and emits visible light. In this process, most of the UV radiation is absorbed (or otherwise blocked) by the fluorescent dye and/or the glass of the bulb. Yet, some does get through.

Fortunately, it seems that typical exposure to the UV light from commonly used types of fluorescent lamps is relatively small. According to the report by the UK Health Protection Agency, fluorescent lighting may add about 3% to the lifetime UV exposure. However, this estimate is imprecise and some lamps may be greater offenders than others. If you spend a lot of time under intense fluorescent light, you could consider extra protection. One possible step is to ensure that fluorescent bulbs have plastic diffusers over them. Depending on the material used in the diffuser, UVA would be reduced by 17-99% and effective UVB by 19-100%."

Don't know how expensive this type of glass is, and I don't know how your tortoise table(?) looks like either, but you could take a look here. Glass.

As for aluminum?

"if I’m in my room, with a lot of windows and I also have a lot of mirrors, can the mirrors additionally reflect the UV light and cause more damage and the short answer is, those mirrors will reflect all the UVA light but none of the UVB light. Let’s take a look at this. Most mirrors are just a piece of flat glass with a coating on the back of aluminum. Some of them have silver, but most of them today are aluminum. We already know that when the light goes through the glass all the UVB is absorbed, so even if you’re at home with your windows open and UVB comes in once it hits the mirror it’s going to be absorbed by the glass, the UVB is gone. But aluminum, the backing on the mirror, is a very effective reflector of UVA and we also know that the glass doesn’t stop the UVA so that’s the reason the mirrors reflect almost all of the UVA light and none of the UVB light."

Also there are two main types: UVA and UVB. A tortoise needs both, "but particularly UVB, the short wavelengths of light, for Vitamin D3 production. Exposure to UVA is important for the activity level, feeding, and breeding in many species.

    * First, UVB cannot penetrate through glass, and it can even be partially blocked with fine mesh. Do  not place a glass top over the cage between the bulb and the animal. If a mesh top is necessary to prevent escapes, select a type with larger openings. (Note: Quality UVB bulbs are specially made, so UVB can pass through their glass.)

    * Second, UVB light from a bulb rapidly loses its intensity the farther away it is placed from your pet. UVB bulbs should generally be placed 12-15 inches above the animal, and no more than 18 inches.

    * Next, when shopping for a UV bulb, it is important to consider the amount of UVB it produces. Research the UVB needs of your species before buying a bulb. Most species do well with a bulb that emits 3-5% UVB, left on for 10-12 hours per day.

    * Finally, UVB bulbs don't last forever. After several months of use, they start to decrease in output. Plan on replacing your bulb about every 10 months, more often for some brands. Keep in mind that this is one of the ongoing costs of keeping a turtle or tortoise. "

It's a science this one
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so having the bulb inside that special glass cover would protect you from the UV-radiation at the same time as it would give you a good view of their habits and behavior I guess

[tommya300]

First, is the type of UV you are using affective?

"ULTRA-VIOLET and SKIN CANCER

At the opposite side of the visible spectrum is the Ultra-Violet, above the blue light. U.V. (for short) is dangerous for life, since it literally destroys cells without immediate alarm.  UV is used to sterilize tools, kill bacteria and germs, and it is responsible for skin cancer.  We have no UV sensor in skin, we can't see UV, so we are totally unprotected from UV. When you are exposed to sun's UV, mostly from 11am to 3pm (UV rays angle enters easily at the Earth atmosphere), your skin is being hit by a massive UV radiation and it leads to all sort of problems. Most severe sun burn is caused more by UV than IR, you will only feel it hours later when your skin will respond to the intense UV attack, red, hot, pain. In real, our body developed the skin's IR sensors as a way to protect ourselves from the immediate danger, the fire, since during all the evolutionary process we were much more exposed to fire (burning bushes, trees, forest) emitting lots of IR, than UV.  As the sun also emits IR, our body always used the IR sensors to indicate sun's intensity, forcing us to look for a shading area, thus, protecting us from dangerous UV.  Later on, tanning at the beach gain a new meaning, sun's heat triggers the skin alarm sensors, but it is ignored and UV is all over your fragile skin.  Ignoring the danger people at the beach think that as hotter the better, well, better for skin cancer.

NOTE:  Eprom erasers use a strong UV light, also known as "germicide lamp". This lamp produces hundreds of times more UV than the sun at noon time, it can erase an eprom memory in minutes, it would take many hours at the sun's light to do the same. Be VERY careful when dealing with those lamps when emitting UV, it can cause SEVERE damage to your eyes or skin, even that the only thing you see is a smooth blue light.  Different from "night club's black light" lamps, UV (germicide lamps) have the bulb made in crystal, regular fluorescent lamps (and the black light ones) use regular glass. Glass is a bad conductor of UV, but crystal is very efficient, this is why germicide lamps uses crystal, so UV can gets out and do its killing work."
http://www.ustr.net/infrared/infrared1.shtml

[RD]

According to Wikipedia Aluminium reflects over 90% of UV ...

 [ Invalid Attachment ]
http://en.wikipedia.org/wiki/Reflectivity

and better UV reflectivity than Silver (Ag) or Gold (Au).

[Don_1 (OP)]

Thanks to you all.

I use a 'Repti glo 5.0'^® UV tube for my tortoises. As the name suggests, they emit 30% UVA and 5% UVB light, which is the correct intensity for tortoises from the sub tropical regions. There are 3% and 10% tubes available for forest and desert dwellers respectively.

The lamps are on for between 12 and 14 hours daily. The shorter days are used on the run up to hibernation, to simulate the natural shortening of daylight hours, which is one of the triggers for the tortoise's preparation to hibernate. As you wrote BC, these tubes have a relatively short life. Although they will last well over a year, only the visible light will be produced. UV light will be significantly reduced after 6 months use and the tube has to be replaced.

The tortoise table they live on during their active time outside of the summer months (Oct. Nov. Mar. Apr.) is in the garage, so we are not constantly exposed to the UV rays. As you suggested, BC, a glass partition could be used as a shield for constant viewing, however, in common with many other reptiles, if a tortoise can see something or somewhere it cannot access, they can get very stressed, so high non transparent sides are the best for their table.

The UV reflective nature of aluminium looks great on that chart. I have now (after much cursing) lined the ceiling of the covered basking section of the table and both Pork Pie & Mr Pastry are happily basking in there under their new tube.

[yor_on]

I think I'll go for a cat instead.
Seems somewhat easier on my nerves?


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Ahh, only after much reflection on the subject of course.

[Geezer]

I think I'll go for a cat instead.
Seems somewhat easier on my nerves?


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Ahh, only after much reflection on the subject of course.

English is an interesting language. It would allow you to say;

"On reflection, I'd prefer a cat."

I'm very poor on other languages, so I don't know if they would allow such a concise statement.

[JP]

So now that that's been answered, how much UV would aluminum reflect?   []

[Geezer]

So now that that's been answered, how much UV would aluminum reflect?   []

The minimium amount.

[yor_on]

Isn't that the aluminimum effect?
On reflection I mean?

As Geezer pointed out