Fish bladder, seaweed, or pork skins… which one is used in brewing beer? If you guessed one — surprise. It’s actually all three. Fish bladder is used to make isinglass, a traditional fining agent that helps clarify beer. It works by binding to yeast and proteins so they clump together and fall out of suspension. That’s how you get that brilliant, polished clarity in styles like British ales. Seaweed — specifically Irish moss (a type of red algae) — is added during the boil. It helps coagulate pr