Re: Header pic
Then the bottle will need a few good whacks to break, which it will, usually uselessly short at the neck.
That's why you should twist the bottle as you hit it against the sharp edge. Didn't they teach you that at school?
I'm not saying I went to a rough school, but the teachers used to break out the riot gear whenever they planned a raid on the smokers in the loos. And one chemistry lesson came to an abrupt end when the Bomb Squad rolled in.