My thermos bottle's instructions say:

Füllen Sie keine kohlensäurehaltigen Flüssigkeiten oder Trockeneis in das Produkt. Füllen Sie keine alkoholischen oder öligen Flüssigkeiten in das Produkt.

This translates to:

Do not fill carbonated liquids or dry ice into the product. Do not fill alcoholic or oily liquids into the product.

I suppose the reason you're not supposed to fill carbonated liquids or dry ice into the thermos bottle is that the bottle isn't able to handle the pressure which builds up if you close the lid. In the case of dry ice, it might also not be able to cope with the temperature of it. I further suppose that oil can wear down the seal.

But why are you not supposed to store alcohol in it? Sure, some alcoholic beverages are carbonated, but those already are excluded. What about beverages like mulled wine?

  • $\begingroup$ What makes you think you shouldn't store alcohol in it? Except for carbonated alcohols as you stated. $\endgroup$
    – Gert
    Dec 5, 2017 at 20:25
  • 4
    $\begingroup$ For all thermos I had alcohol wasn't a problem , I guess. Might some o-ring get brittle/ harder upon prolonged alcoholic storage ? I would say might be with very alcoholic drinks. Zum Voll :) $\endgroup$
    – Alchimista
    Dec 5, 2017 at 20:28
  • 3
    $\begingroup$ One issue is what material comprises the inner lining of the thermos. Typically, the inside of a thermos bottles are silvered glass. But that's not a guarantee and even if it is, there's no guarantee that there isn't a coating on the glass. The coating may degrade in the presence of alcohol. Also, oily substances are hard to clean out, and the manufacturer may not want people to think badly of their product because they couldn't clean it effectively. $\endgroup$
    – Zhe
    Dec 5, 2017 at 20:30
  • $\begingroup$ Storing alcohol in copper is supposed to be a bad idea, because the oxide layer on the copper could oxidise ethanol. Not sure on what timescale that would happen. Stainless steel should be inert i think, and certainly glass is inert. There is no coating in a thermos, because that would certainly degrade when you fill in hot water. $\endgroup$
    – Karl
    Dec 5, 2017 at 21:10
  • 2
    $\begingroup$ The only reason I have a thermos is to fill it with boozed tea... $\endgroup$ Dec 6, 2017 at 11:42


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