Don't apologise in the least! [This conversation is getting better and better, really. He's having fun, and his smile is more genuine now.]

Actually... You sound a lot like my coworkers. I work with medics and chemists, and many of them sound like you when they talk about their work. [Then he leans in, and places a hand on the man's arm.]

Not that I'm insulting you, mind. I enjoy listening to one's passions, especially when it comes to creating something out of another.