Blow up
It seems 'blow up' can mean make something bigger or explode, but in balloon context, how do we tell what it means. For example,
1. I want to blow up the balloon.

Does it mean I want to pop it, or I want to make it bigger?
Or did I understand the phrase wrong?
Thank you. :)

Question

Blow up
It seems 'blow up' can mean make something bigger or explode, but in balloon context, how do we tell what it means. For example,
1. I want to blow up the balloon.

Does it mean I want to pop it, or I want to make it bigger?
Or did I understand the phrase wrong? 
Thank you. :)

Answer

Blow up when referring to a balloon means to blow air into it to expand it.
The expression to bust a balloon is to “pop a balloon”

Answer

How about 'the balloon blows up itself?' Does it mean it becomes bigger or it pops? :)
It's confusing.

Answer

In the balloon context, it means to make it bigger (to blow air into it). If you want it to explode, you want to "pop" it :)