Aluminum Foil: Shiny side up, or down?

[Shel_B]

This evening I'm cooking a lasagna and have covered the dish with aluminum foil. While covering the dish, it occurred to me that I wasn't sure if the shiny side should be up, facing away from the lasagna, or down. And what about with other dishes, assorted casseroles, or just reheating leftovers in the oven? Is there a correct way of using the foil? Does it make much difference? I seem to recall some recipes which were specific. So, what's the story?

[heidih]

According to America's Test Kitchen the heat conductivity is the same. The dull versus shiny is an artifact of the manufacturing process. LINK HERE That said, I generally see shiny side up, and out of habit do that. I think it comes on the roll that way - when you pull and tear, the shiny side is facing you with the dull side ready to face the dish.

[IndyRob]

For lasagna, I might choose shiny side down only because, if there's cheese on top, it will tend to stick less to the smoother surface (although negligibly so).

However, in this case the foil is used primarily to stop (or slow) premature browning. Is this by blocking direct radiation, or by creating a humid zone? I don't know. If it's the former, then perhaps the added reflectivity of the shiny side would better on the outside. But I suspect it's the latter. In that case, the heat energy spent turning water into steam will have a cooling effect that will dwarf the conductivity/reflectivity of the foil.

[dcarch]

"----then perhaps the added reflectivity of the shiny side would better on the outside. ---"

Reflectivity will be the same, shiny or matt will make no difference in energy reflected.

The difference is in the pattern of reflected energy. One is directional the other is more random.

dcarch

[IndyRob]

"----then perhaps the added reflectivity of the shiny side would better on the outside. ---"

Reflectivity will be the same, shiny or matt will make no difference in energy reflected.

The difference is in the pattern of reflected energy. One is directional the other is more random.

dcarch

A mirror is a better reflector than a piece of aluminum. A random reflector will reflect some of the energy into itself. And certainly, a black surface absorbs more energy than either. However, that's probably of no consequence when we're basically maintaining a cloud of steam under the foil.

Edited July 26, 2013 by IndyRob (log)

[FauxPas]

I was told that the shiny side should always be toward the food, but I can't remember where I heard (or read) this, so not sure if it has a lot of validity. :-)

[dcarch]

I think the word shinny is a misleading term. In fact the reflectivity of the base material, aluminum is just as shinny even the finish is matt, and not mirror like.

I cannot use the term coherent light because that means a different light wave behavior.

The light reflected by a mirror-like surface is more organized directionally, while a matt surface reflects light in many directions, but the quantity of reflected light remains the same.

For instance, if you take a mirror and break that into many small pieces, with each piece aiming at a slightly different direction, you will no longer see a "shinny" reflection, but the reflected light is still the same quantity.

dcarch

[dcarch]

I was told that the shiny side should always be toward the food, but I can't remember where I heard (or read) this, so not sure if it has a lot of validity. :-)

In a test by the American Test Kitchen, it made no difference.

dcarch

[PattyO]

Or, you could use Reynold's Non-Stick, which I LOVE, especially for Italian dishes like lasagna. The non-stick side is even labelled.

[FauxPas]

Or, you could use Reynold's Non-Stick, which I LOVE, especially for Italian dishes like lasagna. The non-stick side is even labelled.

That's probably the only time that the 'sides' matter! :-)

[Tri2Cook]

On an episode of the show "How It's Made", they visited a factory that makes aluminum foil. They asked that very question and the reply was "it really makes no difference whatsoever".

[Shel_B]

Or, you could use Reynold's Non-Stick, which I LOVE, especially for Italian dishes like lasagna. The non-stick side is even labelled.

How is the foil made to be nonstick? Are coatings or chemicals used? Is the foil rolled in some way to make it nonstick?

[rotuts]

in the very first season of Test Kitchen they made lasagna with no-boil noodles. an Rx Ive used a lot to rave review. in that show they sprayed the aluminum foil lightly with oil-spray and that side was the down side.

I had never seen that before and it works very well if you have concerns of foil sticking to you dish.

might be cheaper to get reg. Al foil and a can of spray than the non-stick foil.

[Toliver]

Or, you could use Reynold's Non-Stick, which I LOVE, especially for Italian dishes like lasagna. The non-stick side is even labelled.

This. The melted cheese doesn't stick to the foil.