I have seen the commercial about the new beer can where it is vented by puncturing a whole on the can (air behind water). If you just pour normally with normal cans it will get bottle necked and the pour is not smooth.
This morning I opened a new bag of milk by cutting a small opening at the top corner of the bag. I noticed the milk always pours smoothly through that one opening.
Why is the pour smooth coming out of a bag but not from a can?
I am uncertain what I should be tagging this with, if someone can add some relevant tags it would be appreciated. Also remove this paragraph once done, thanks