Why do people recommend separating drinking glasses that are stuck together by cooling the inner glass and heating the outer glass?

Question

I have seen mutliple people recommend this. Here is why it confused me:

If you had a large balloon stuck in the center of an inner-tube, and you wanted to separate them quickly, you would want both the baloon and the inner-tube to contract toward their centers.

If the baloon was slowly deflating (by losing air or cooling down), and you wanted it to stay stuck, you would want the inner-tube to inflate (by adding air or heating up) in order to keep its grip.

So, why are people recommending to expand one glass while shrinking the other? Won’t that just maintain the grip by the outer glass? Don’t we want to cool both glasses, so they both take up less space, creating air between them?

In: 0

Answer 1

Things usually expand when heated and contract when cooled. If the outer glass expands and the inner glass contracts there will be more room between the inner and outer glasses. If you cool both then both contract and there isn’t any more space between them.