Does Aluminum Foil Really Create Hot Spots?

T

T.H.Cammo

Well-Known Member
I believe this is one of those "urban legends" that just keeps getting passed along and everyone just believes it. Because, well, why not?

The only way I could see this being true would be if all of those little "crinkely surfaces" were to be "Focused" on a small area. And that just doesn't seem very likely at all! It would have to be like that episode of "Mythbusters" where they tried to light a boat on fire using polished bronze shields to reflect the sun (it was extreamly difficult to organize). With the "randomness" of crinkled foil it would be impossible to focus on anything. Badda-bing - Badda-bang, no focus - no Hot Spot! Am I missing something?

I would be very interested in hearing from anybody that has actually suffered from these "Hot Spots" (I seriousely doubt that anyone ever has!). I would also like to hear from anybody that can explain how a "hot spot" might actually be created by reflecting off of aluminum foil (either flat or crinkeled).

Another thing, while I'm on a rant about aluminum foil, if aluminum foil has such a low reflectivity index; why are all the best commercial reflectors made out of aluminum? This paradox bothered me years ago, it still does!
 
T

T.H.Cammo

Well-Known Member
That's pretty much what I expected - no responces at all! Although I did put this in the wrong forum by accident!

1. No one has ever actually had a "Hot Spot" because they used aluminum foil?
2. No one can even explain why that is "supposed" to happen?
 
BeaverHuntr

BeaverHuntr

Well-Known Member
Hot Spots has always been a urban myth none the less why would you even want to use Aluminum Foil in the first place ?Because its cheaper?? Dude a gallon of flat white paint is pretty cheap too and has much better reflectivity than Aluminum foil. Aluminum has a lot less reflectivity than mylar or good ol' cheap flat white paint. Just my 2 cents
 
CaptainCAVEMAN

CaptainCAVEMAN

Well-Known Member
BeaverHuntr said:
Hot Spots has always been a urban myth none the less why would you even want to use Aluminum Foil in the first place ?Because its cheaper?? Dude a gallon of flat white paint is pretty cheap too and has much better reflectivity than Aluminum foil. Aluminum has a lot less reflectivity than mylar or good ol' cheap flat white paint. Just my 2 cents
Click to expand...
That's the only response needed.
 
wtxmale

wtxmale

Member
Wow,,,been in the paint business for 35 years,,really you think flat paint is reflective,,,NOT !! the scale runs from flat ( o% reflective) satin some reflective,,,semi gloss..more ref. and gloss alot of ref.. high gloss,,,most ref. you can prove this easily...paint a board with all these types of sheen,,,shine a light on it,,,now you will see what ref. and what does not...flat paint absorbs light,,not reflect!
 
wtxmale

wtxmale

Member
if you want to see how reflective alum. foil is,,,try this test,,,2 baking potatoes,,,wrap each in tin foil,,,but one shinny side out the other shinny side in,,,put in oven at rec. temp (325) wait an hour and remove them,,,shinny side out,,hard not cooked!! shinny side in,,cooked ready to eat! aluminum foil is a great as a reflector,,,but it also reflects heat,,where as a board painted with high gloss paint will reflect light but very little heat.
 
BeaverHuntr

BeaverHuntr

Well-Known Member
wtxmale said:
Wow,,,been in the paint business for 35 years,,really you think flat paint is reflective,,,NOT !! the scale runs from flat ( o% reflective) satin some reflective,,,semi gloss..more ref. and gloss alot of ref.. high gloss,,,most ref. you can prove this easily...paint a board with all these types of sheen,,,shine a light on it,,,now you will see what ref. and what does not...flat paint absorbs light,,not reflect!
Click to expand...


Material: Reflectivity: Mylar 90 &#8211; 98 % Foylon 92 - 95 % BW poly 85 - 90 % Flat white paint 60 - 90 % Mirror 82 - 87 % Glossy white paint 70 - 80 % Aluminium foil (flat side) 50 - 70 % Black paint < 10 %
 
wtxmale

wtxmale

Member
Not true,,,need to check your facts...i've been in R&D with dow chem for 15 years now,,my main research has been in reflectivity of latex paint and how it affects light refraction.....latex flat paint is between 8 and 12 %...high gloss...72-80 %....aluminum foil shinny or refective side 93-98 % these are facts ...the main reason for using gloss white over aluminum is that gloss wht reflects light not heat,,,alum. foil reflects heat also.
 
billybob420

billybob420

Well-Known Member
wtxmale said:
Not true,,,need to check your facts...i've been in R&D with dow chem for 15 years now,,my main research has been in reflectivity of latex paint and how it affects light refraction.....latex flat paint is between 8 and 12 %...high gloss...72-80 %....aluminum foil shinny or refective side 93-98 % these are facts ...
Click to expand...
Fuck dow chem.

Kill yourself.


Seriously.
 
ru4r34l

ru4r34l

Well-Known Member
wtxmale said:
Not true,,,need to check your facts...i've been in R&D with dow chem for 15 years now,,my main research has been in reflectivity of latex paint and how it affects light refraction.....latex flat paint is between 8 and 12 %...high gloss...72-80 %....aluminum foil shinny or refective side 93-98 % these are facts ...
Click to expand...
Did your R&D at DOW give you any time to research specular vs diffused reflection? Maybe your grade 1 teacher could have told you white does not absorb light, have you ever stopped to think why solar panels cells are black?

come on now, I hope you boss at DOW is'nt on here!

Dow Chemical paper on Elastomeric Roof Coverings

DOW Form No. 832-00209-0711 BBI said:
In 1991, the Committee on Science, Engineering and
Public Policy of the National Academy of Sciences,
National Academy of Engineering and the Institute of
Medicine published a report titled Policy Implications
of Greenhouse Warming. One mitigation option in their
findings was the use of “white surfaces” “… to reduce
air conditioning use and the urban heat island effect by
25% through planting vegetation and painting roofs white
at 50% of U.S. residences.”
Click to expand...
regards,
 
You must log in or register to reply here.
Top