“There will be no foolish wand-waving or silly incantations in this class. As such, I don’t expect many of you to appreciate the subtle science and exact art that is potion-making. However, for those select few who possess the predisposition, I can teach you how to bewitch the mind and ensnare the senses. I can tell you how to bottle fame, brew glory, and even put a stopper in death.”
the reason Seamus accidentally blows stuff up is because he’s too busy paying attention to Dean and he loses his focus so he messes up his potions and spells causing explosions and he just plays along with it like, “Bloody shit, can’t say I’m surprised”. Then he goes all red ‘cause Dean just saw the whole thing. Like, could you just imagine how cute it’d look.