Being an avid coffee drinker, I finally gave in to temptation and bought myself a stainless steel insulated cup (not of Yeti brand, which sell for a ridiculously high price), and I'm extremely happy with it...
Anyway, it's become obvious (and I've also checked online) that these things can keep liquids cold for a very long time. Leftover ice will linger in there for a little more than 24 hours if the lid is in place and properly shut. (Do they really hold a vacuum between their inner and outer walls, as this Amazon ad states?). But warm liquids are a different story, they will cool down to room temperature in about 6 hours.
My question is, why is this thing better at keeping something cold inside, than keeping it hot? Why is easier for heat to leak out instead of creeping in? I suspect it has something to do with the lid, since heat travels upward... but I'm not 100% sure.
Anyway, it's become obvious (and I've also checked online) that these things can keep liquids cold for a very long time. Leftover ice will linger in there for a little more than 24 hours if the lid is in place and properly shut. (Do they really hold a vacuum between their inner and outer walls, as this Amazon ad states?). But warm liquids are a different story, they will cool down to room temperature in about 6 hours.
My question is, why is this thing better at keeping something cold inside, than keeping it hot? Why is easier for heat to leak out instead of creeping in? I suspect it has something to do with the lid, since heat travels upward... but I'm not 100% sure.