Why does aluminum foil have one shiny side and one with a matte finish?

https://bookofjoe2.blogspot.com/2025/10/why-does-aluminum-foil-have-one-shiny.html

49•surprisetalk•4d ago

Comments

dnemmers•4d ago

“The final rolling is therefore done on a sandwich of two sheets, face to face.”

slau•1h ago

Whomever wrote that clearly has never made or eaten a sandwich. Without something in between the two layers, it’s hardly a sandwich.

mjevans•1h ago

The foil is the 'meat' the rollers are the bread.

perilunar•1h ago

An open sandwich can have two layers.

volemo•1h ago

Not homogenous though.

perilunar•1h ago

If it was any more homogeneous it would just be a piece of bread.

socalgal2•1h ago

that's not a sandwich, it's a pizza

perilunar•1h ago

A pizza is an open sandwich

ekropotin•1h ago

No, pizza is a toast per Cube Rule - https://cuberule.com/

perilunar•1h ago

Toast is an open sandwich, unless it has no topping, in which case it is just bread. Also their definition of cake as having multiple layers makes no sense, and would rule out most actual cakes.

doodlebugging•1h ago

>An open sandwich can have two layers.(..)

...and if one layer is meat and the other is a perfect meat vehicle, like a tortilla, you can simply fold it over the meat and wrap all the meat goodness is the proper warmth of a tortilla. Food, the way food was intended.

CLPadvocate•4d ago

> Yet many people persist in calling aluminum foil "tinfoil."

> We chemists get annoyed at things like that.

> Now, about aluminum foil.

Actually, most chemists are profoundly annoyed at the Americans' inability to spell aluminium properly...

CamperBob2•1h ago

IUPAC recognizes both spellings.

Also, speak up, we can't hear you from all the way up here ON THE MOON.

foobarbecue•1h ago

It's cold and lonely here on the moon. -- Jonathan Coulton

antonvs•1h ago

Did visiting the moon damage your hearing? Last I checked there haven’t been any Americans on the moon for over half a century.

Perhaps if you used the metric system…

hacker_homie•1h ago

They do use the metric system at NASA maybe that’s why they haven’t been back to the moon.

antonvs•1h ago

Yes but their US contractors don’t all use metric, which is what caused them to miss Mars that one time.

r2_pilot•1h ago

If I recall correctly they didn't miss Mars. Quite the opposite, really.

JSR_FDED•32m ago

Mars missed them?

doodlebugging•48m ago

...and the SAE system like me (older American here) then you would be able to provide the answers that confuse your audience the most when they ask about volumes, velocities, dimensions, etc. and you would have as much fun in life as I have had. Your metric system is for people who need to have things simplified in order for them to be understandable and relatable. It's about as dumbed down as you can make something. Lowest common denominator type stuff. Americans have always thrived on challenge and that is why we stupidly cling to the complexity of the SAE system of units. It fits so we sits.

st_goliath•29m ago

> can't hear you from all the way up here ON THE MOON.

cough

https://www.quora.com/What-does-the-German-phrase-Hinter-dem...

dpe82•1h ago

Sir Humphry Davy first isolated the stuff and he called it aluminum, so that's good enough for me.

st_goliath•45m ago

Well, the name Davy originally proposed was alumium.

I propose we switch to that instead, so everyone can be annoyed equally and in the same way.

dpe82•26m ago

I accept your proposal; alumium it is.

thomassmith65•1h ago

It isn't clear if that is a dig at Americans having their own spelling of aluminum/aluminium, or ignorance that Americans have their own spelling.

elric•27m ago

> Actually, most chemists are profoundly annoyed at the Americans' inability to spell aluminium properly...

That's just patently false. Anyone who's had any sort of education in chemistry/physics is aware of the history of the word and doesn't give a damn.

gethly•19m ago

Try to make them pronounce nuclear instead of nucelar :D

monocasa•16m ago

Humphrey Davy, the British chemist who performed early work to isolate the element, and who initially named it, called it 'aluminum'. Americans mostly followed him, but the British changed later at the complaints of the French, Swedish, and Germans that it used essentially English roots rather than Latin ones. Which, considering that we now have elements named such things as Tennessine, seems to be a bit of an argument that doesn't quite apply anymore.

johng•3d ago

I always heard the shiny side reflected heat better. So that side should face food you are trying to heat up in the oven.

Any truth to that I wonder?

ahhhhnoooo•1h ago

No. Aluminum foil has the same material properties with respect to convection and conduction of heat no matter which side faces out. The only heat that would be different would be radiated heat, which your food won't have a ton of, and even then, the dull side is still quite reflective. It's maybe one of those "technically" correct statements that the shiny side reflects more heat, but for the application of cooking, the impact is effectively zero. The retention of steam is going to be such a larger factor the side you use will effectively make no difference.

hamstergene•1h ago

I can speak for myself: when I ask if the shiny side reflects the heat better, I don't mean to also ask if the difference is significant. It's really just curiosity, whether my school physics intuition holds up or lies to me, that's all.

So, "technically yes" is good enough answer for me.

sdeframond•1h ago

Is it technically true, though? The matte side has a difuse reflection, which does not mean it reflects less. It just scatters more.

sawjet•1h ago

The shiny and dull sides look like perfect mirrors in IR wavelengths.

rocqua•13m ago

I recall similar advice around mylar heat blankets. Perhaps those got mixed up?

rich_sasha•1h ago

Which side is better at reflecting woke beams from space?

NewCzech•1h ago

People deeply understand the physics of tinfoil hats. A properly constructed tinfoil hat needs two layers, with the shiny sides facing in opposite directions. Only the shiny side reflects brain waves. You need to reflect in both directions: one direction keeps the government from using waves to put ideas in your head; the other is to keep the government from reading your mind.

kombookcha•15m ago

For you mindwarriors out there who like to go on the offence, leave a removable fold over your third eye so you can quickly flip it open and be ready to engage in PSI-combat on the astral plane or realspace as the situation requires.

Etheryte•1h ago

The study [0] linked at the bottom of the article has good insights on that, plus it's a marvelous read all around.

[0] https://web.archive.org/web/20060612212953/http://people.csa...

red75prime•1h ago

Aren't they from somewhat below waist level a parte posteriori?

botusaurus•1h ago

so if you skipped the final rolling it would be shiny on both sides?

is this being produced?

jmward01•41m ago

I believe 'heavy duty' foil is sold. I don't have any to check but my guess is both sides are shiny. In fact, I think I remember both sides being shiny the last time I used it...

ZeWaka•15m ago

It's 3.33x thicker, yes - we use it in foodservice. (0.8mm vs 0.24mm)

gethly•20m ago

aluminium :D

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Why does aluminum foil have one shiny side and one with a matte finish?

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