Update: sorry to be an OP who didn’t deliver. My buddy never made the measurement. I’m hoping he will. Sorry everyone!

This is all I found on their site about it, which aligns but isn’t as much detail as I hoped

With standard and heavy duty foil, it’s perfectly fine to place your food on either side so you can decide if you prefer to have the shiny or dull side facing out.

Okay, my buddy is gonna take foil tomorrow and run it over the profilometer (?) tomorrow and see. I’ll report back with more numbers and less hand waving when I have it

It was a fair few years ago, but yeah, the oxidation on it will be so much smoother than the delta in surface roughness that I doubt it’d make much difference. Lemme reach out to a metallurgist from there and see what he thinks!

Correct. Just a manufacturing decision. It looks a lot more different than it actually is.

Yup, the lab could tell a difference! Shiney side (so mill roller facing, as opposed to the dull side which faces the other layer of aluminum) was marginally more reflective, but I believe (and a former coworker also remembered it as) it was less than a tenth of a percent (<0.1% for the visual folks)

Anyone who says it affects cooking time or something is mistaken, I’d wager.

Former process engineer in an aluminum factory. Aluminum foil is only shiny on one side and duller on the other for process reasons, not for any “turn this part towards baking, etc” reasons.

It’s just easier to double it on itself and machine it to double thickness than it is to hit single thickness precision, especially given how much more tensile strength it gives it.

Also, our QA lab did all kinds of tests on it to settle arguments. The amount of heat reflected/absorbed between the two sides is trivially small. But if you like one side better you should wrap it that way, for sure!

Did you hear what happened to the cyber criminal?

She ransomware