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As the title says, is the aluminium foil still usable in this condition?

If you notice, there's a very obvious white portion in the center of the aluminum foil and the entire roll is like that. Usually when I buy it from the store, it is pure silver without the white line. However when I keep it for some time, this white line appears which appears to me that the foil could be "spoilt"?

Aluminium foil with white stripe

May I also ask what is the name of the condition of this aluminum foil and what causes it to be like this.

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  • What potential problem do you see? It just looks like it have been formed to a pan.
    – paparazzo
    Oct 3, 2018 at 21:04
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    @paparazzo it's the whitish line in the middle.
    – Astralis
    Oct 3, 2018 at 21:04
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    the horizontal non-shiny stripe looks like it may be oxidation (aluminum oxide), which is the aluminum equivalent of rust. I have no idea if it's an issue for food safety.
    – Joe
    Oct 3, 2018 at 21:07
  • @Joe Now you do (see answer) ;-)
    – Fabby
    Oct 3, 2018 at 22:36
  • Odd looking stripe. Are you keeping The Al near a volatile acid or base?
    – Wayfaring Stranger
    Oct 5, 2018 at 22:49

1 Answer 1

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That's just aluminium oxide (Al2O3) and it's harmless as:

  • it's insoluble in water
  • it's nearly insoluble in alcohol.
  • is very hard (Basically the same material as a ruby or a sapphire)
  • it's chemically nearly inert
  • Is basically the same substance as the non-shiny side of the Aluminium foil

So it's definitely useable for all intents and purposes. (including cooking ;-) )

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    It's also just a thicker layer of what all aluminium foil has on the surface.
    – Chris H
    Oct 4, 2018 at 6:31
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    not doubting you, however i can't help but to ask if there's any studies or sources to prove this? My parents are health freak but i have so much of such foils at home. If i can't convince them, they are all going to waste.
    – Astralis
    Oct 4, 2018 at 19:17
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    @Astralis if you want scientific proof: send the foil off to a chemical lab and have it tested and provide the test results to your parents. From where I am across the Internet, that's what it looks like with a high certitude, but without a sample, I cannot test this in my lab... ¯\_(ツ)_/¯
    – Fabby
    Oct 4, 2018 at 19:50

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