<p>I understand that polished aluminum surface reflects more that white. However , the white surface re-emits more energy  so the net affect is that the white retains less energy. </p>

CC BY-SA 3.0
2017-07-04T20:14:47.830Z
A white sheet re-emits energy?  That sounds odd. You mean it emits infrared?  Or does it re-emit UV?  I'm guessing what you mean is that a piece of foil will feel hot to touch where as a white sheet won't feel as hot to touch.
Ensa
CC BY-SA 3.0
2017-07-04T23:11:24.080Z
It emits photons in a wide range,  The data I saw was for white paint and aluminum paint on a steel surface , it did not separate it into spectrum rangers.
blacksmith37
CC BY-SA 3.0
2017-07-05T03:44:47.003Z
@blacksmith37 Then a link to this data/study would be desirable.
John
CC BY-SA 3.0
2017-07-06T14:31:17.820Z
It was done in the 70's by someone in the oil industry. It simply measured the temperature increase of steel with various colors of coating to evaluate heat absorption by oil storage tanks. I don't recall anything else.
blacksmith37
CC BY-SA 3.0
2017-07-11T09:59:56.487Z
So here's context because I don't have my answer.  If a human lies upon a white sheet and another identical human lies on a sun shade (Mylar?), which human will get the most UVB reflected on to them, assuming maximal UVB is present?
Ensa
CC BY-SA 3.0
2017-07-04T19:04:42.323Z
2017-07-04T19:04:42.323Z
blacksmith37
<p>Which reflects more UVB from the sun, a flat laying white cloth sheet, or a flat laying aluminum sheet? Ie. Which material would reflect a wavelength of 280 to 315 nm best?</p>

CC BY-SA 3.0
2017-07-04T10:43:10.653Z
Hi Ensa, welcome to stackexchange. I've edited your question down to just the question, and removed where you had directed it specifically to one person (who may or may not see it).

However, I'm not sure that it's on-topic here. It appears to be a question about the reflectivity of two particular man-made materials to specific wavelengths of light, which isn't obviously earth science to my mind. It might do better on Physics.SE, or Engineering.SE, or possibly a materials science if there is one.
Semidiurnal Simon
CC BY-SA 3.0
2017-07-05T03:31:25.917Z
There is a difference between diffuse reflectance and specular reflectance. An aluminium sheet will tend to have higher specular reflectance (but not as high as a mirror). So you will get nearly complete reflectance of all wavelengths aside from any absorption due to oxide coating on the surface and warming of the metal by infrared. However that will follow angle-of-incidence equals angle-of-reflection. Diffuse reflectance from a mat white sheet will reflect in all directions.
haresfur
CC BY-SA 3.0
2017-07-05T07:25:25.260Z
This question can be made more on-topic if you give some context; I assume it is about geo-engineering.
Jan Doggen
<meteorology>
Relative UVB reflectance of white cloth vs aluminum
Ensa
# Relative UVB reflectance of white cloth vs aluminum

(Asked by: username_0 on 2017-07-03)

Which reflects more UVB from the sun, a flat laying white cloth sheet, or a flat laying aluminum sheet? Ie. Which material would reflect a wavelength of 280 to 315 nm best?

**Tags:** meteorology

> **Comments:**
> **username_1**: Hi username_0, welcome to stackexchange. I've edited your question down to just the question, and removed where you had directed it specifically to one person (who may or may not see it).  However, I'm not sure that it's on-topic here. It appears to be a question about the reflectivity of two particular man-made materials to specific wavelengths of light, which isn't obviously earth science to my mind. It might do better on Physics.SE, or Engineering.SE, or possibly a materials science if there is one.  
> **username_2**: There is a difference between diffuse reflectance and specular reflectance. An aluminium sheet will tend to have higher specular reflectance (but not as high as a mirror). So you will get nearly complete reflectance of all wavelengths aside from any absorption due to oxide coating on the surface and warming of the metal by infrared. However that will follow angle-of-incidence equals angle-of-reflection. Diffuse reflectance from a mat white sheet will reflect in all directions.  
> **username_3**: This question can be made more on-topic if you give some context; I assume it is about geo-engineering.  

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## 1 answers

### Answer by username_4 on 2017-07-04. Score: 1 | Accepted answer

I understand that polished aluminum surface reflects more that white. However , the white surface re-emits more energy so the net affect is that the white retains less energy.

> **Comments:**
> **username_0**: A white sheet re-emits energy?  That sounds odd. You mean it emits infrared?  Or does it re-emit UV?  I'm guessing what you mean is that a piece of foil will feel hot to touch where as a white sheet won't feel as hot to touch.  
> **username_4**: It emits photons in a wide range,  The data I saw was for white paint and aluminum paint on a steel surface , it did not separate it into spectrum rangers.  
> **username_5**: @username_4 Then a link to this data/study would be desirable.  
> **username_4**: It was done in the 70's by someone in the oil industry. It simply measured the temperature increase of steel with various colors of coating to evaluate heat absorption by oil storage tanks. I don't recall anything else.  
> **username_0**: So here's context because I don't have my answer.  If a human lies upon a white sheet and another identical human lies on a sun shade (Mylar?), which human will get the most UVB reflected on to them, assuming maximal UVB is present?  

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