Acidity is the difference between a cocktail that tastes crisp and “finished” and one that feels flat, heavy, or overly sweet. It is also one of the fastest ways to improve consistency: citrus changes from day to day, while a measured approach to acidity can keep a drink tasting the way it was designed.

Foam is not just decoration. Done well, it adds aroma at the rim, changes mouthfeel, and can rebalance a drink by softening sharp edges or carrying a top-note flavor into every sip. Done poorly, it collapses fast, tastes “eggy” or bitter, and makes service inconsistent. This guide explains what cocktail foam is, why it forms, the main foam styles used in bars, and how to make foam reliable in real service. It is technique-only and focuses on stability, workflow, and troubles