> My thermos is 5-6 years old and completely made of steel. I don’t
> see any reason for buying a fragile one with a glass core as the steel
> ones are just as good if not better, or so I’m told.
Glass conducts heat poorly (i.e., good for a thermos), while metals conduct heat very well (i.e., poor for a thermos). The “Thermos” company agrees that glass is the best insulator,
On Thermos containers: The inner component is always glass. It’s a consumer version of a “Dewar flask.” The outside is typically plastic, but the “heavy duty” ones are sometimes metal.
On shipping dry ice. If you can avoid it, avoid it. You will pay absurd penalties for it as it’s considered a hazardous material. (It can asphxyiate a cargo plane’s crew, if they don’t know about it and place it in the right compartment of the plane.)
No it’s not. If I had a digital camera I could prove it to you as mine is entirely metal (with a plastic and rubber cork). I’m pretty sure most thermoses sold in Finland are of this variety.
It works by enclosing a vacuum (or close to that) between two metallic bottles inside of each other joined at the top.
All the Thermoses I’ve encountered are silvered glass on the inside. They may look like metal, but drop a spoon into one, and you’ll get a broken Thermos for your efforts.
I’ve got a couple travel coffee mugs that are stainless steel inside and out, with space between the two, but they’re not Thermos containers.
