Stormblast Bolts : How it works plz ?

Stormblast Bolts: once launched, the explosion is only triggered once a detonator is thrown onto the mines.

My question is: if I launch Stormblast Bolts with my build 2 and then launch the detonator with my build 1, will the damage from my Stormblast Bolts be counted via my build 1 or 2? Thanks in advance and enjoy the game!