先讲一件挺离谱的事。 假设你雇了一个装修队，说好把家里所有的木质门窗换成铝合金的。三个月后，装修队跟你说"完工了，验收吧"。你走进屋子，开关门都很顺畅，风也不漏，一切正常。你签字付钱。结果后来你才发现，装修队压根没换材料，只是把木头门刷成了银色。

What makes a flask worth your money is its ability to slow down heat transfer – either in or out – via a layer of almost airless space sandwiched between the flask’s inner and outer walls. Depending ...