OOOPS sorry for the typo in title...I meant shiny side...HAHA! No way to edit...

Shiny goes to the outside.

(Looks nicer.)

Are you talking about baking? or Roasting?

The shiny side is down (inside) If the shiny side is on the outside it reflects the heat. Not sure where I read that, but it must have been 30 years ago. My guess is that it probably is minimal so it won't really matter. But I will continue to have dull side out anyway.

Ann

Like Ann, I always put the dull side outside because I learned in physics that shiny reflects heat and dull absorbs it.

I do the same as Ann and Colleen but Alexa is likely right. I bet it makes no difference. The release foil is another matter. The dull side doesn't stick. I use it for anything I dip in chocolate.

The following is from Ask A Scientist on the US Dept of Energy Website:

*********************************************************

Question - Hello. I have a question that I am sure you will have the answer to. What side
of the aluminum foil should be on the outside when I wrap something up in it to keep warm or
cold? The shiny side or the dull?
I was at a grill out last week and was told that the shiny side should be on the inside and
the dull side of the aluminum foil should be on the outside.
----------------------
Connie,

The shiny side is slightly better reflector of heat. Face that side of the foil in the
appropriate direction. To keep things cold, put the shiny side on the outside -- that
will reflect incoming heat. To keep things warm, face the shiny side inward toward the
hot food -- to reflect the heat that is trying to escape back into the food.

Note that people often bake potatoes with the shiny side out -- that is because it makes
for a better (prettier) presentation. In reality, baking them that way reflects the
incoming heat on the outside, slightly slowing the cooking process.

Of course, in reality, which side of the foil faces where makes little difference. It does
make for lively conversation, though.

Regards,
ProfHoff 686
=====================================================
There is no difference in which side you use. The difference in the surface of aluminum
foil is a result of the manufacturing process and has no bearing on heat retention or
reflection.

Chris Murphy
=====================================================
As a practical matter, it probably does not matter because convection is overwhelming
any difference in reflectance of shiny vs. dull side of the foil. The science is that
you are balancing the E = K* T^4 law, where T is the absolute temperature in kelvins,
K is a constant, and E is the energy transferred. The value of 'K' depends upon the
details of the reflectance of the surface. But the target "hamburger-in-foil-on-the-grill"
is, in practice, very complicated. The charcoal is radiating heat to the burger from below
(which is highly variable depending upon the surface temperature of the coals. On top the
burger-foil is losing heat energy to the surroundings, but it is virtually impossible to
assign an "average" temperature to the surroundings. To make matters worse, the aluminum
foil is "crinkled" so that the reflecting surface is not uniform, and on the "dull" side
the reflectance is not even specular, i.e. there is a range of angles of reflection for a
specified angle of incidence, and that "range" depends upon the angle of reflectance.

Now what DOES make a difference with respect to aluminum foil in general, either on the
grill or in the oven is this. DO NOT let the aluminum foil contact an acidic ingredient,
like tomato sauce, catsup.. At oven (or grill) temperature the acidic ingredient will
dissolve the aluminum foil. Although Al(+3) is not especially toxic, contact with acidic
foods at high temperature should be avoided.

Vince Calder
=====================================================
Connie,

Short answer: I believe that the dull side should be out.

Long answer:

That would be my answer too. The only real scientific basis that I can think of for this
answer is: Radiative heating / cooling. I have done no experiments to prove one way or
the other though. The goal is to maximize heat transfer. Heat transfer can happen by
CONDUCTIVE, CONVECTIVE, and RADIATIVE means.

Conductive heating will happen by the hot grill in direct contact with the foil. This
mode is limited by the thermal conductivity of the foil.

Convective heating will happen by the hot air movement around the foil and transferring
its heat to the surface. Then it will also be limited by the a heat transfer coefficient
based on how fast the air is moving and of course the temperature difference between the
foil and the hot air.

Radiative heating will happen by the absorption of infrared radiation (IR radiation) or
heat emanating from all around the food (within the BBQ). Now please consider infrared
radiation to be in the wavelength range of 880 nanometers or so. Realize that this
wavelength of "light" is very near the color red in the visible portion of the spectrum.
Further, this means that the radiation will act like light and the foil shall act as a
mirror. Knowing now that you want to transmit (foil to absorb all radiation) as much IR
through the foil as possible. It should be clear to you that the dull side should be
OUTWARD facing so as not to minimize the reflection of IR radiation.

Hope this helps,
Darin Wagner

Here is a link that might be useful: Ask a scientist

from Reynolds' faq:

Which side of Reynolds Wrap Aluminum Foil should I use, the shiny or the dull side?

Actually, it makes no difference which side of the aluminum foil you useÂboth sides do the same fine job of cooking, freezing and storing food. The difference in appearance between dull and shiny is due to the foil manufacturing process. In the final rolling step, two layers of foil are passed through the rolling mill at the same time. The side coming in contact with the mill's highly polished steel rollers becomes shiny. The other side, not coming in contact with the heavy rollers, comes out with a dull or matte finish.

The exception is when using Reynolds Wrap® Release® Non-Stick Aluminum Foil. The non-stick coating is applied during manufacturing to the dull side of the foil. Always place the non-stick (dull) side toward the food.

You mean my Mom fibbed to me!!!!!! All those years of making sure it was shiny side in to cook . No wonder I'm a mess!

ROFL Sharon! Guess there are a lot of us who are messes.

LOL Chase!

When I cook with tin foil I don't pay much attention to which side to use so it's good to know that I haven't been using it the "wrong way". :-)

But when I use tin foil for wrapping I always show the shinny side out because it's prettier!

Al

My mother always said shiny side up - she swore by that! Much later I found out that it makes no difference. I don't think she lied about it... just that's what SHE believed. Old habits are hard to break, though, and although I know, intellectually, that it makes no difference, it's sort of hard to use it dull side up.

So Sharon and Beverly, count me among the messes! LOL

I always figured the shiny side goes up, or out, because it is prettier, kind of the way you put the pretty side of wrapping paper to the outside. Works for presents, so why not for cooking.

And in the middle of summer when you sleep with just the sheets, pattern side down so the fold is pretty or pattern side up so the bulk of the bed is pretty? Or should you just avoid one-sided sheets in the summer?

ROFL FOAS! That is a "Hot Topic" in my family/group.

DM always had the shiny side out when using foil. I do the same. Love, love that release foil.

David

FOAS:
Pattern side down so the fold is pretty and a gorgeous hand-made, light weight quilt on top so the bulk of the bed is pretty.

Of course, mine would be MUCH prettier if I'd make it!! LOL

Foil? Meh. However I happen to grab it.
I re-use it and by the time I'm done, there's not much shiny anywhere!

Deanna

Like Deanna's, mine gets grabbed and used however it lands, I don't pay any attention to one side or the other, I just figure I'm lucky that I have some and didn't run out when I needed it.

I also "recycle" aluminum foil, so it could be any darned side out by the time I'm done with it.

Grandma always told me it didn't make a difference either, that I should stop being so "obsessive" about things and just cook something. I try to follow her advice, which is why such things usually don't bother me one way or the other. That, or I'm lazy, LOL.

I've never tried the "release" type of foil, somehow I just know I'd get the wrong side up!

Annie

Let's not even get into if the toilet paper goes over the top or under....

Foil: shiny side out.

Toilet paper: rolls out from the top.

Sheets: I like to "sleep between the colors," as a long ago boyfriend once said. :)

If you have a cat, you know you should roll toilet paper from the bottom.

dcarch

I know, I am off topic. :-)

If you have a cat, you know you should roll toilet paper from the bottom.

Or if you have a toddler. I was staunch over-hand until I had kids. Thanks for reminding me that perhaps they're ready for me try hanging it "correctly" again!

My Mom actually wrote Reynolds and their response was "it does not matter, both sides cook with the same results".

I also wrote to Reynolds once I receive the same response as Klancie.