- Joined
- Dec 17, 2013
- Messages
- 34
Hi, guys.
In a long discussion in another thread, ( http://www.tortoiseforum.org/thread-83263.html ) on the causes of pyramiding, the subject of basking lamps came up. A question was raised about my comment that short-wavelength infrared was vital for basking, but there were additional concerns with artificial lamps vs natural sunlight. As the discussion on that thread has continued into nutritional concerns, I'm posting about infrared separately, here.
The infrared story is very interesting. It is something I only started looking at in the last year or two and it all ties in really well with the UVB story, and it is quite theoretical. Basically, it is to do with the interaction of sunlight and water.
"Sunlight" is arbitrarily sub-divided by scientists into UV, Visible, and Infrared wavelengths.
Infrared is subdivided by scientists into infrared-A (IR-A, 780–1400 nm) and infrared-B (IR-B, 1400–3000 nm) and infrared-C (IR-C, 3000 nm–1 mm).
The infrared wavelengths of sunlight are almost all in the shorter wavelengths called IR-A. There is a small amount of IR-B but no IR-C.
IR-A wavelengths are very close to red light, and indeed they work very much like red light; they can go through the skin and penetrate deep into the body. Think how, if you shine a bright torch against the back of your hand in a dark room, you can see the red light coming through your palm. IR-A will gently warm through the entire body of a small reptile as it basks. Bigger ones will of course take a lot longer to warm up.
There is something special about the IR-A from sunlight, though, that needs mentioning.
Our earth's atmosphere contains a great deal of moisture - water vapour and droplets - in the miles of atmospheric gas filtering the light from the sun. Water absorbs very specific wavelengths of the sun's radiation. When it absorbs this energy, it warms up. The wavelengths in the IR-A region that are absorbed by water can be detected very easily by looking at a spectrum of sunlight, in the IR-A region. Where the water has absorbed the IR-A, it is in effect "used up", and so is missing from the spectrum; so you can see a big dip in the irradiance at this point. Here is a solar spectrum as it is in outer space (the yellow blocked-in part) and how it is on the earth's surface (the red blocked-in part) and you can see the big dips taken out of it by atmospheric water vapour, which are labelled (Hâ‚‚O):
(Image created by Robert A. Rohde / Global Warming Art
http://www.globalwarmingart.com/wiki/File:Solar_Spectrum_png)
I'll explain why this is important later on.
But the sun also warms the substrate, rocks, trees etc. Objects warmed by the sun re-radiate this heat in the longer wavelengths (IR-B and IR-C) that are also invisible, but can often be felt - hold your hand just above a hot sun-warmed rock and you will feel the long-wavelength heat as a prickly warmth on your skin. This long-wavelength infrared doesn't go deep. It hits the surface of the skin and immediately gives up its heat energy to the skin surface. It will warm the surface very fast, but the heat will need to warm deeper layers by conduction, a much slower process.
Indoors, we create IR-A with basking lamps (incandescent light bulbs, halogen bulbs, mercury vapour lamps and metal halides). Heat sources that do not also give off light, such as ceramic heaters, heat plates, and heat mats emit mainly longer wavelengths - IR-B and IR-C.
So it makes sense to use non-light-emitting heat sources for warming the air and the background environment, in the way that warm air and warm soil throws back heat after the sun has been on it all day.... In cooler northern climates, we typically place these to provide suitable ambient temperatures in areas that the tortoise will move around in when not basking.
And then we use basking lamps emitting visible light and IR-A when we are providing "sunlight" for basking species, and it makes sense to hang these lamps above the tortoise, like the sun.
But now we have to consider the difference between the infrared from a basking lamp and the infrared from natural sunlight.
This graph shows the spectrum of a halogen lamp (in red), so that you can compare it with the solar spectrum (in green).
from: http://3dprinter.wikidot.com/dlp-projectors-optics
You'll notice that the halogen lamp doesn't have the big dips in its spectrum, caused by several miles of water vapour and droplets taking out the energy from those wavelengths. The halogen lamp also has a lot more IR-B than sunlight, and it also has some IR-C. So when the tortoise basks under a basking lamp, he gets ALL the IR-A wavelengths, including the wavelengths that are missing from the sunlight, plus some IR-B and IR-C.
But the IR-A wavelengths missing from sunlight are the wavelengths that are most readily absorbed by water molecules. Since the lamp is at most, 1-2ft above the tortoise, not several miles away, there cannot ever be enough atmospheric water vapour between him and the lamp to absorb those wavelengths. So where are the first water molecules those wavelengths encounter? ... inside the cells of the tortoise's carapace and skin! These immediately absorb the energy from those wavelengths of IR-A... creating heat in the carapace and skin.
The other IR-A wavelengths penetrate deeper and release their warming energy through all the body tissues, but these "dump" all their energy into the water inside the very top layers of skin and keratin....
And so do the IR-B and IR-C wavelengths.
This sounds like it might well be a problem for parts of the body evolved to receive mainly sunlight, which has little or none of these wavelengths present...
I would love to know whether it is an important factor in pyramiding....
There is a growing use of red and infrared light in healing of wounds and stimulating the body's repair after injury, in human and veterinary medicine. Red lasers are mainly used, but a new technique using "water-filtered IR-A" is being pioneered by some German people and it looks very promising.
For example: "Water-filtered infrared-A (wIRA) in acute and chronic wounds"
The idea is to have a thin layer of water in a special tray inside the lamp unit. It is terribly expensive and totally impractical for us as keepers, but it does look interesting. Here is something I just found on Wikipedia, showing a spectrum of "water-filtered IR-A" - see how the water is removing quite a large amount of those "water" wavelengths from the halogen lamp spectrum, and how there are other filters which remove the longer-wavelength IR-B and IR-C, too.
From: http://commons.wikimedia.org/wiki/File:WIRA-Wiki-GH-017E-en-Spectra-wIRA-sun-halogen-radiators.png
By Helmut Piazena (Helmut Piazena) [CC-BY-SA-3.0-de (http://creativecommons.org/licenses/by-sa/3.0/de/deed.en) ], via Wikimedia Commons.
So what do we, as reptile-keepers, do?
We have no alternative but to use some form of basking lamps and heaters, if we choose to keep ectotherms far from their natural habitats, in climates where they cannot survive outdoors. And if we use them carefully, combinations of incandescent lamps, halides, mercury vapour lamps, fluorescent tubes and even ceramic heaters have proven their worth over decades of successful reptile-keeping. But now we are becoming aware of the inevitable risks that our artificial heat and light sources carry with them.... I don't think there is cause for alarm, or drastic measures. But I'm sure there are things we can do to reduce the risks of too-intense localised heating - which is what seems to be the main issue here.
First, look at Testudoresearch's work with thermal imaging cameras.
Here's the forum post summarising it: http://www.tortoiseforum.org/thread-83263-post-787129.html#pid787129
Any tortoise with cold head and legs (blue in the first picture) is going to hang around longer under a heat source until his whole body is warm. If the heat source is a small circle - a "basking spot" - close under a small halogen lamp (as sold by SO many reptile stores as a "basking lamp") then only the top of the carapace is being heated, possibly quite severely overheated and dried out at the same time, as these images suggest. And how long will he have to stand there, cooking his carapace, to get his core temperature up to the right level...?
So the first very positive step is for every basking "spot" to be converted into a basking "zone", with all sunlight wavelengths (heat, light and UV) covering, as evenly as possible, an area AT LEAST as large as the WHOLE tortoise with his legs and head fully extended. They will happily bask like that, given a big enough zone....
And to obtain this big zone, keepers will almost certainly need to take the second very positive step - moving the lamps further away from the tortoise, and changing all "spot" bulbs to "flood" bulbs. This will spread the beam of heat and light over a wider area. Often, with larger tortoises, it is best to arrange two, three or even more bulbs to cover a large enough area. I've seen this done very effectively in some zoos, using a combination of PAR38 flood halogen or tungsten incandescent bulbs and UV-emitting lamps.
This of course requires the tortoises to be kept in suitably large enclosures or tortoise tables to allow a big basking zone and a big cooler area with a gradient between, and hides/ shelters. In my experience, it is extremely difficult if not impossible to achieve anything satisfactory in anything smaller than 4ft long....
Well... I guess that's my "take" on infrared lighting, to date.... I know I have a lot more to learn, and I'm sure others will chip in with their experiences and practical suggestions...? I am trialling the use of rectangular, outdoor floodlamps which have long thin so-called "linear halogen" R7s bulbs; in the UK these are widely used to light backyards and the sides of houses. They create much wider basking zones than "round" light bulbs. But they seem almost unknown in the States and in other European countries... PAR38 floods seem the next best thing.
And metal halides may be very well worth researching. They have far less IR-B and IR-C than incandescent bulbs and halogens... and a lot better quality visible light, too.
Frances Baines
www.uvguide.co.uk
In a long discussion in another thread, ( http://www.tortoiseforum.org/thread-83263.html ) on the causes of pyramiding, the subject of basking lamps came up. A question was raised about my comment that short-wavelength infrared was vital for basking, but there were additional concerns with artificial lamps vs natural sunlight. As the discussion on that thread has continued into nutritional concerns, I'm posting about infrared separately, here.
The infrared story is very interesting. It is something I only started looking at in the last year or two and it all ties in really well with the UVB story, and it is quite theoretical. Basically, it is to do with the interaction of sunlight and water.
"Sunlight" is arbitrarily sub-divided by scientists into UV, Visible, and Infrared wavelengths.
Infrared is subdivided by scientists into infrared-A (IR-A, 780–1400 nm) and infrared-B (IR-B, 1400–3000 nm) and infrared-C (IR-C, 3000 nm–1 mm).
The infrared wavelengths of sunlight are almost all in the shorter wavelengths called IR-A. There is a small amount of IR-B but no IR-C.
IR-A wavelengths are very close to red light, and indeed they work very much like red light; they can go through the skin and penetrate deep into the body. Think how, if you shine a bright torch against the back of your hand in a dark room, you can see the red light coming through your palm. IR-A will gently warm through the entire body of a small reptile as it basks. Bigger ones will of course take a lot longer to warm up.
There is something special about the IR-A from sunlight, though, that needs mentioning.
Our earth's atmosphere contains a great deal of moisture - water vapour and droplets - in the miles of atmospheric gas filtering the light from the sun. Water absorbs very specific wavelengths of the sun's radiation. When it absorbs this energy, it warms up. The wavelengths in the IR-A region that are absorbed by water can be detected very easily by looking at a spectrum of sunlight, in the IR-A region. Where the water has absorbed the IR-A, it is in effect "used up", and so is missing from the spectrum; so you can see a big dip in the irradiance at this point. Here is a solar spectrum as it is in outer space (the yellow blocked-in part) and how it is on the earth's surface (the red blocked-in part) and you can see the big dips taken out of it by atmospheric water vapour, which are labelled (Hâ‚‚O):
(Image created by Robert A. Rohde / Global Warming Art
http://www.globalwarmingart.com/wiki/File:Solar_Spectrum_png)
I'll explain why this is important later on.
But the sun also warms the substrate, rocks, trees etc. Objects warmed by the sun re-radiate this heat in the longer wavelengths (IR-B and IR-C) that are also invisible, but can often be felt - hold your hand just above a hot sun-warmed rock and you will feel the long-wavelength heat as a prickly warmth on your skin. This long-wavelength infrared doesn't go deep. It hits the surface of the skin and immediately gives up its heat energy to the skin surface. It will warm the surface very fast, but the heat will need to warm deeper layers by conduction, a much slower process.
Indoors, we create IR-A with basking lamps (incandescent light bulbs, halogen bulbs, mercury vapour lamps and metal halides). Heat sources that do not also give off light, such as ceramic heaters, heat plates, and heat mats emit mainly longer wavelengths - IR-B and IR-C.
So it makes sense to use non-light-emitting heat sources for warming the air and the background environment, in the way that warm air and warm soil throws back heat after the sun has been on it all day.... In cooler northern climates, we typically place these to provide suitable ambient temperatures in areas that the tortoise will move around in when not basking.
And then we use basking lamps emitting visible light and IR-A when we are providing "sunlight" for basking species, and it makes sense to hang these lamps above the tortoise, like the sun.
But now we have to consider the difference between the infrared from a basking lamp and the infrared from natural sunlight.
This graph shows the spectrum of a halogen lamp (in red), so that you can compare it with the solar spectrum (in green).
from: http://3dprinter.wikidot.com/dlp-projectors-optics
You'll notice that the halogen lamp doesn't have the big dips in its spectrum, caused by several miles of water vapour and droplets taking out the energy from those wavelengths. The halogen lamp also has a lot more IR-B than sunlight, and it also has some IR-C. So when the tortoise basks under a basking lamp, he gets ALL the IR-A wavelengths, including the wavelengths that are missing from the sunlight, plus some IR-B and IR-C.
But the IR-A wavelengths missing from sunlight are the wavelengths that are most readily absorbed by water molecules. Since the lamp is at most, 1-2ft above the tortoise, not several miles away, there cannot ever be enough atmospheric water vapour between him and the lamp to absorb those wavelengths. So where are the first water molecules those wavelengths encounter? ... inside the cells of the tortoise's carapace and skin! These immediately absorb the energy from those wavelengths of IR-A... creating heat in the carapace and skin.
The other IR-A wavelengths penetrate deeper and release their warming energy through all the body tissues, but these "dump" all their energy into the water inside the very top layers of skin and keratin....
And so do the IR-B and IR-C wavelengths.
This sounds like it might well be a problem for parts of the body evolved to receive mainly sunlight, which has little or none of these wavelengths present...
I would love to know whether it is an important factor in pyramiding....
There is a growing use of red and infrared light in healing of wounds and stimulating the body's repair after injury, in human and veterinary medicine. Red lasers are mainly used, but a new technique using "water-filtered IR-A" is being pioneered by some German people and it looks very promising.
For example: "Water-filtered infrared-A (wIRA) in acute and chronic wounds"
The idea is to have a thin layer of water in a special tray inside the lamp unit. It is terribly expensive and totally impractical for us as keepers, but it does look interesting. Here is something I just found on Wikipedia, showing a spectrum of "water-filtered IR-A" - see how the water is removing quite a large amount of those "water" wavelengths from the halogen lamp spectrum, and how there are other filters which remove the longer-wavelength IR-B and IR-C, too.
From: http://commons.wikimedia.org/wiki/File:WIRA-Wiki-GH-017E-en-Spectra-wIRA-sun-halogen-radiators.png
By Helmut Piazena (Helmut Piazena) [CC-BY-SA-3.0-de (http://creativecommons.org/licenses/by-sa/3.0/de/deed.en) ], via Wikimedia Commons.
So what do we, as reptile-keepers, do?
We have no alternative but to use some form of basking lamps and heaters, if we choose to keep ectotherms far from their natural habitats, in climates where they cannot survive outdoors. And if we use them carefully, combinations of incandescent lamps, halides, mercury vapour lamps, fluorescent tubes and even ceramic heaters have proven their worth over decades of successful reptile-keeping. But now we are becoming aware of the inevitable risks that our artificial heat and light sources carry with them.... I don't think there is cause for alarm, or drastic measures. But I'm sure there are things we can do to reduce the risks of too-intense localised heating - which is what seems to be the main issue here.
First, look at Testudoresearch's work with thermal imaging cameras.
Here's the forum post summarising it: http://www.tortoiseforum.org/thread-83263-post-787129.html#pid787129
Any tortoise with cold head and legs (blue in the first picture) is going to hang around longer under a heat source until his whole body is warm. If the heat source is a small circle - a "basking spot" - close under a small halogen lamp (as sold by SO many reptile stores as a "basking lamp") then only the top of the carapace is being heated, possibly quite severely overheated and dried out at the same time, as these images suggest. And how long will he have to stand there, cooking his carapace, to get his core temperature up to the right level...?
So the first very positive step is for every basking "spot" to be converted into a basking "zone", with all sunlight wavelengths (heat, light and UV) covering, as evenly as possible, an area AT LEAST as large as the WHOLE tortoise with his legs and head fully extended. They will happily bask like that, given a big enough zone....
And to obtain this big zone, keepers will almost certainly need to take the second very positive step - moving the lamps further away from the tortoise, and changing all "spot" bulbs to "flood" bulbs. This will spread the beam of heat and light over a wider area. Often, with larger tortoises, it is best to arrange two, three or even more bulbs to cover a large enough area. I've seen this done very effectively in some zoos, using a combination of PAR38 flood halogen or tungsten incandescent bulbs and UV-emitting lamps.
This of course requires the tortoises to be kept in suitably large enclosures or tortoise tables to allow a big basking zone and a big cooler area with a gradient between, and hides/ shelters. In my experience, it is extremely difficult if not impossible to achieve anything satisfactory in anything smaller than 4ft long....
Well... I guess that's my "take" on infrared lighting, to date.... I know I have a lot more to learn, and I'm sure others will chip in with their experiences and practical suggestions...? I am trialling the use of rectangular, outdoor floodlamps which have long thin so-called "linear halogen" R7s bulbs; in the UK these are widely used to light backyards and the sides of houses. They create much wider basking zones than "round" light bulbs. But they seem almost unknown in the States and in other European countries... PAR38 floods seem the next best thing.
And metal halides may be very well worth researching. They have far less IR-B and IR-C than incandescent bulbs and halogens... and a lot better quality visible light, too.
Frances Baines
www.uvguide.co.uk