Which fining agent is commonly used to clarify beer?

Isinglass is commonly used as a fining agent to clarify beer due to its effectiveness in settling unwanted particles and haze-forming proteins. Derived from the swim bladders of fish, isinglass works by binding to these particles to form larger aggregates, which can then be easily removed from the beer, typically through sedimentation or filtration. This process enhances the beer's clarity and presentation, making it more visually appealing to consumers.

While other fining agents like bentonite and gelatin are also employed in the brewing process, isinglass is particularly favored in traditional beer styles and among many brewers for its reliability and efficiency. Activated charcoal, on the other hand, is primarily used for removing undesirable flavors and aromas rather than for clarification, which sets it apart from isinglass and the other agents mentioned.