Mirrored Reflector Behind UVB

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Re: Mirrored Reflector Behind UVB

Postby Claudiusx » Mon Feb 24, 2020 11:09 am

Well then can you clarify,

Are you stating that aluminum foil... being a milled surface... should only increase output by 50%? Since you stated that milled aluminum only reflects 50%

Or can you elaborate on why you bring up the topic of buying a sheet of aluminum instead when the topic of using foil came up?

Like I said, my own testing shows that the aluminum foil I'm using is near a 100% increase, which is disagreeing with what you're saying.

I guess what I'm asking is, why suggest the sheet of aluminum that you buff and polish yourself instead of just using aluminum foil? Interested in your reasoning behind that.

-Brandon
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Re: Mirrored Reflector Behind UVB

Postby Claudiusx » Mon Feb 24, 2020 11:12 am

Moved by Moderator from Enclosures to Advanced Discussion
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Re: Mirrored Reflector Behind UVB

Postby kingofnobbys » Mon Feb 24, 2020 10:06 pm

The increase you are seeing is the optical effect of the UV that would otherwise be lost being reflected and concentrated by the "mirrored" reflector surface.
Added as afterthought to show how it works to concentrate "light" :
Image
Very same principle but in reverse as used in parabolic solar collectors (using parabolic shaped reflector troughs).
ref Duffie, J.A. Beckman, W., Solar Engineering of Thermal Processes, Chapter 7: the introduction through Section 7.10. pp. 354-358.
Simply put , no reflector , less than 1/3 or 1/4 the UV emitted from the UV source is directed at the basking reptile, add a parabolic reflector and if it's got a good UV reflective surface then intensity of the UV flux received by the basking reptile is increased by the reflector directing otherwise wasted UV towards the reptile ( the effect is additive and highly sensitive to the surfaces reflectivity ) .


See the links already provided.

Regards Al foil , depending on it's end purpose , it's rolled with different tempers in thicknesses between 5 microns and 200 microns.
The tolerance ( Perry's Chem Eng HB ) is +/- 8% in gauge (thickness), for 5 micron foil (like you probably have in the pantry) , the tolerance is 400 nm ( not bad for visible light , not so flash for UV ).

CeO nanopowder has a particle size of 50 to 80 nm , this is commonly used in producing precision optical surfaces ( lens faces and mirrors , and in metallography ).

Now a little physics : for good reflection , the rule is one half wavelength is the minimum tolerance for a good surface , so for UV at 200 nm , the aim is 100 nm surface roughness , aim used where wavefront distortion is not as important as cost ( as in the case of reflector hood ).
Last edited by kingofnobbys on Tue Feb 25, 2020 8:30 am, edited 4 times in total.
CBDs: Cleopatra & Caesar born 28Jan19.
Puff (RIP 10Dec15),Rex (RIP 16Mar17),Toothless (RIP 26Nov17).Peppa (RIP 22Mar19).
EBTSs : George & Mildred (born july 2010).
EWSs : , Fluffy (F) rescued injured by lawnwacker 14Nov17, Gutzy (F) rescued 27Sep19 - RIP 3Aug20 (est 12 yo), Wriggles (F) - injured rescue, over 8 yrs old, RIP 2Feb16 old age. Lucky juvenile (M) - cat attack rescue (lost r-eye, broken r-lower jaw), fatal SI RIP 21Jul2010.
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Re: Mirrored Reflector Behind UVB

Postby Claudiusx » Mon Feb 24, 2020 11:35 pm

Yes I understand that "wasted" uv is being redirected.
But you still recommended using a sheet of aluminum that you polish yourself. Just wondering why you'd suggest this over using foil. That's what I dont understand. Why youd suggest doing something so much more expensive and complicated. especially when nearly every household already has aluminum foil that can be used to get the same basic outcome as a typical commerical working reflector.

If you are mimicking the effect of a good commercial reflector with aluminum foil anyways, what extra benefit does your recommendation give? Unless you have another reason for your suggestion, that's what I'm asking.

-Brandon
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Re: Mirrored Reflector Behind UVB

Postby kingofnobbys » Tue Feb 25, 2020 4:56 am

claudiusx wrote:Yes I understand that "wasted" uv is being redirected.
But you still recommended using a sheet of aluminum that you polish yourself. Just wondering why you'd suggest this over using foil. That's what I dont understand. Why youd suggest doing something so much more expensive and complicated. especially when nearly every household already has aluminum foil that can be used to get the same basic outcome as a typical commerical working reflector.

If you are mimicking the effect of a good commercial reflector with aluminum foil anyways, what extra benefit does your recommendation give? Unless you have another reason for your suggestion, that's what I'm asking.

-Brandon


Food grade aluminium foil is not treated to prevent surface corrosion ( formation of Al203 that starts immediately on exposure the air and immediately impacts the UV reflectivity).
Foil is very delicate to work with ( as anyone who has used to wrap baked chunks of meat can attest.
Foil will not hold the shape , so a substrate is needed to form to shape and the foil needs to be attached to this.

FYI the reflectance of Al203 in UV is very poor.
Image
ref Antireflective bilayer coatings based on Al2O3 film for UV region
K.MARSZAŁEK, P.WINKOWSKI, M.MARSZAŁEK
Materials Science-Poland, 33(1), 2015, pp. 6-10

This is why astronomical reflecting telescopes have "PROTECTED Al" as the reflective surface, the protection is provided by a thin optical layer of pure SiO2 ( which is transparent to UV ) and protects the vapor deposited optical film of pure aluminium from oxidation.

I think the large gain in reflectivity is worth the little bit of extra effort. PLUS foil is exceedingly delicate to work with and very easy to damage , a polished sheet of aluminium is strong and there is a choice of tempers and alloys ( chemistries) , is very durable and will hold the bend to form the parabolic-like profile.
Aluminium sheet comes in a choice of thickness between 0.5mm to 6.0mm for flat sheet and coil,

A bottle of CeO slurry can be readily acquired from any hardware shop , any chop-shop will know all about it as it's commonly used to polish car panels before and after painting , and by stone masons , to that nice slick finish).

So if a commercial reptile specific slip on reflector or reflector hood is not an option, and you must make your own , do it once , do it right .
Last edited by kingofnobbys on Tue Feb 25, 2020 8:33 am, edited 1 time in total.
CBDs: Cleopatra & Caesar born 28Jan19.
Puff (RIP 10Dec15),Rex (RIP 16Mar17),Toothless (RIP 26Nov17).Peppa (RIP 22Mar19).
EBTSs : George & Mildred (born july 2010).
EWSs : , Fluffy (F) rescued injured by lawnwacker 14Nov17, Gutzy (F) rescued 27Sep19 - RIP 3Aug20 (est 12 yo), Wriggles (F) - injured rescue, over 8 yrs old, RIP 2Feb16 old age. Lucky juvenile (M) - cat attack rescue (lost r-eye, broken r-lower jaw), fatal SI RIP 21Jul2010.
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Re: Mirrored Reflector Behind UVB

Postby Claudiusx » Tue Feb 25, 2020 7:48 am

Thank you that's all I wanted, a simple reason.

I'm not trying to complicate it for people, I'm trying to simply help them. The best option is buying a new working reflector, but in the interim aluminum foil will work. And that will be what I will continue to suggest.

The only issue you have with it that could be an issue imo is the corrosion of the surface. However, I've been running one so far for 3 months and have not noted any decrease in performance from original.
Your point about being flimsy and not holding shape is easily remedied by making the foil a couple layers thick.

Replacing aluminum foil reflectors (if necessary) every few months is a lot cheaper and easier than buying a sheet of aluminum that you need to polish every few months. Unless you expect people to coat their own sheets in silicone dioxide. Because simply polishing it with cerium oxide will not protect the surface from corrosion. still not sure how quickly any noticable effects from corrosion take, but I will be monitoring it every month to check output.

I'm gonna keep it simple and easy for everyone and continue to recommend aluminum foil over going out and buying, polishing, and protecting a sheet of aluminum. Sometimes the simplest solution is the best solution.

Thanks for your input though.

-Brandon
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Re: Mirrored Reflector Behind UVB

Postby kingofnobbys » Tue Feb 25, 2020 8:38 am

claudiusx wrote:Thank you that's all I wanted, a simple reason.

I'm not trying to complicate it for people, I'm trying to simply help them. The best option is buying a new working reflector, but in the interim aluminum foil will work. And that will be what I will continue to suggest.

The only issue you have with it that could be an issue imo is the corrosion of the surface. However, I've been running one so far for 3 months and have not noted any decrease in performance from original.
Your point about being flimsy and not holding shape is easily remedied by making the foil a couple layers thick.

Replacing aluminum foil reflectors (if necessary) every few months is a lot cheaper and easier than buying a sheet of aluminum that you need to polish every few months. Unless you expect people to coat their own sheets in silicone dioxide. Because simply polishing it with cerium oxide will not protect the surface from corrosion. still not sure how quickly any noticable effects from corrosion take, but I will be monitoring it every month to check output.
There are aluminium grades that are highly resistant to passivation of the surface , much more so than the grades used in domestic aluminium foil.

I'm gonna keep it simple and easy for everyone and continue to recommend aluminum foil over going out and buying, polishing, and protecting a sheet of aluminum. Sometimes the simplest solution is the best solution.

Thanks for your input though.

-Brandon
CBDs: Cleopatra & Caesar born 28Jan19.
Puff (RIP 10Dec15),Rex (RIP 16Mar17),Toothless (RIP 26Nov17).Peppa (RIP 22Mar19).
EBTSs : George & Mildred (born july 2010).
EWSs : , Fluffy (F) rescued injured by lawnwacker 14Nov17, Gutzy (F) rescued 27Sep19 - RIP 3Aug20 (est 12 yo), Wriggles (F) - injured rescue, over 8 yrs old, RIP 2Feb16 old age. Lucky juvenile (M) - cat attack rescue (lost r-eye, broken r-lower jaw), fatal SI RIP 21Jul2010.
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