In the past few decades, Guinness revolutionized both draft beer systems and how stouts are canned. The key? Nitrogen, and a modified ping pong ball. You’re drinking a can of Guinness. As you near the ...

You’re drinking a can of Guinness. As you near the bottom, something rattles around inside the can. You look inside and see, to your surprise, what looks like a ping pong ball. Was it a factory error?

In the past few decades, Guinness revolutionized both draft beer systems and how stouts are canned. The key? Nitrogen, and a modified ping pong ball. Amelia Schwartz is a Brooklyn-based writer and ...