Had a discussion a while back with Mrs G about aluminium foil. Remembered about it earlier when foiling the tray to cook food.

I know, it’s exciting. Please try to contain yourselves.

My opinion is the shiny side should face up to reflect the heat to help cooking. Mrs G said it should be the other way round with the matt side facing up.

Which way is correct?

While i am on the subject, which way should food be wrapped? Shiny in or shiny out? Haven’t had this discussion, just an added question for even more excitement 😀

Yes, this is what my life has become 😕

Shiny side out for hats.

I would say it’s irrelevant. Foil isn’t there to reflect heat, it’s there to form a “lid” and keep moisture in.

I initially assumed there was a plastic layer making it shiny on one side, and hence your food would be less in contact with metallic aluminium. Some foils are made this way – on a packet of Polos you can scrape the foil off the plastic. However normal alu foil is not made this way, so it doesn’t matter.

Hang on.

Foiling the tray to cook the food? You are both wrong.

While i am on the subject, which way should food be wrapped?

To keep it airtight? In a tupperware box.

Matt side out to absorb heat, shiny side in to reflect heat back into whatever you’re cooking.

What I was always told and seems logical but never questioned the science!!

Foiling the tray to cook the food?

In my house that’s code for “Dear God this grill pan is minging but I can’t be arsed cleaning it so I’ll put some foil in it instead” 😆

Ha to be fair that happens here.

I’ve also had to fish the grill pan out of the bin twice because “its too dirty to clean”

And thats whete caustic soda comes in…

Its just an artefact of how the foil is manufactured. Theres no purpose or effect of the two different finishes

But what I want to know is… on a roll of sellotape how does the glue know to stick to one side of the tape but not the other when its rolled up?

[video]https://www.youtube.com/watch?v=XDGtWen2Lqw[/video]

😀

What macruiskan said.

From my extensive ‘how it’s made’ viewing he is correct.

In the final rolling they can’t set the rollers close enough together to get it that thin, so they take feeds from two separate foil rolls and roll them together under one roller set to its minimum thickness, then separate the two sheets once it comes back out.

Where the foil touches the roller it produces one surface, and where it touches the other foil gives it the other finish. However sadly I don’t think Mr how it’s made voice-over said which one was made by which so we can now argue about that!

Shiny side in when wrapping up a bit of fish, shiny side down when lining a grill pan and cooking sausages as I reckon it reduces spitting and the flare ups/smoke.

Shiny side touches the rollers during manufacture and may have traces of [food safe] oil on it*. Dull side is theoretically cleaner. Ergo: Dull side to the food. The difference in infrared reflectivity between the two finishes is negligible.

*Extremely esoteric reason for being aware of this.

Which side to bite with your teeth?

I read an article about this exact topic recently but for the life of me can’t recall where it was.

The difference in reflectivity is negligible, so don’t worry about it.

molgrips – Member
I initially assumed there was a plastic layer making it shiny on one side, and hence your food would be less in contact with metallic aluminium. Some foils are made this way – on a packet of Polos you can scrape the foil off the plastic. However normal alu foil is not made this way, so it doesn’t matter.

Good post… 🙂

shiny side in to reflect heat back into whatever you’re cooking

are you cooking with the sun?

i thought the only point of foiling the tray is so you don’t have to wash it up

I would say it’s irrelevant. Foil isn’t there to reflect heat, it’s there to form a “lid” and keep moisture in.

So does that make it a pie, or a casserole with a lid…?

i thought the only point of foiling the tray is so you don’t have to wash it up

This ^^

Bitvwasteful no?

are you cooking with the sun?

Actually – I hardly ever use foil for anything.

The last time I did in any quantity was leading a workshop about solar ovens. Quite a fascinating movement of designers and aid agencies developing cooking and water pasteurisation ovens for communities around the world (half the world’s population) who still cook on open wood fires.

Each design solution has to take into account the local economy (whether people buy from shops, buy from local cottage industries or make things themselves) the latitude and the times of day that people traditionally eat.

So you get fabulous fresnal-shaped ovens for making lunch in equatorial counties when the sun is high and clamshell shaped ones for making breakfast in south africa when the sun is on the horizon.

We made an oven from a cardboard box, a roll of tinfoil, and lemonade bottle and a coke can that could pasteurise water in about 30 minutes on a autumn afternoon in Lincolnshire.

In that application the shiny side probably matters.

i thought the only point of foiling the tray is so you don’t have to wash it up

This is why i was foiling the tray, the tray is clean. Just reminded me of the discussion we had so thought i would ask. Some interesting points though.

We’ve started using greaseproof paper instead of foil.

Not really sure why, I suspect it was all the Spar had left, but it’s much better for actually cooking on – no more random bits of foil stuck to the bottom of your roasties.

I guess it might also be slightly more eco than dumping aluminium in the bin?

Ally foil is awesome for keeping stuff fresh in the fridge. Coriander, chopped onions & celery keep well for ages.

Is it cheaper to use a few layers of economy foil, or one layer of ‘spensive thick foil

tillydog – Member

Shiny side touches the rollers during manufacture and may have traces of [food safe] oil on it*. Dull side is theoretically cleaner.

Doesn’t the dull side then touch the shiny side when it is rolled up onto the cardboard sleeve?

It’s dull side towards the food, Mrs G is correct.

I’ve read this somewhere authoritative a while back but I cannot for the life of me remember where now.

We made an oven from a cardboard box, a roll of tinfoil, and lemonade bottle and a coke can that could pasteurise water in about 30 minutes on a autumn afternoon in Lincolnshire

They scale up well…

9600 mirrors, 3500°C in a few seconds

Project time! (might need a few rolls of foil…)

Wow that’s impressive! Surely this brilliant use of free-energy will be for the betterment of all mankind?

“The high temperature materials division use the furnace to evaluate radome survival during MIRV warhead earth re-entry along with investigating other material properties under the “high energy thermal radiation environment” frequently produced by nuclear devices.”

Oh. 😐