is actually a reason for it.
Temperature Can Make a Difference
One of the interesting things about plastic milk containers is that their contents and the surrounding environment can affect the pressure inside.
Milk is refrigerated.
It gets transported.
It sits in cool storage.
It gets loaded into a shopping cart.
It goes into your car.
Then it goes into your refrigerator.
All of those temperature changes can affect the air and gases inside the container.
The plastic is flexible enough to respond.
So the jug can change shape slightly.
