How does the next paragraph end?

How to separate stuck glasses
Understand how glass responds to heat.
Most commonly, glasses get stuck together when they are stacked immediately after they are washed. Glass expands when heated, and contracts as it cools, and this is sufficient to stick glasses together in some cases.
Never fear: you can use this to separate the glasses. You will need to cool the inner glass and heat the outer glass in order to free them from each other.