Before electrical firing became the preferred method, it was "in your face" fireworks. My first chance to send the big shells upward will NEVER be forgotten, something I expect every pyrotechnician will agree with.
You are no longer a hundred feet away, or fifty, or even ten. The fuse only extends a few inches out of each mortar. You step up to the mortar line, crouch down and make sure your head and body are well away from the mouth of the mortar. Your free hand removes the fuse safety cap from one shell and then your other hand touches the fire to that little black fuse. You now only have time to turn your back to the mortar and take a crouched step or two away. The fuse burns slowly for a few seconds, but when it enters the paper fuse tube, the wait is over.
Sixty feet per second is the fuse burn rate now, so it is just a few thousandths of a second before WHAM, the shell is on its way up. You hear and FEEL the explosion that propels the shell skyward.
The audience hears a WHUMP but you feel a whump and hear a BOOM. Your heart races as adrenalin adds to the excitement. You have just done something so very few people ever get the chance to do. You want to fire the next shell now and it is an even larger diameter shell.