What can contribute to flat beer if dirty glassware is used?

Using dirty glassware can significantly impact the carbonation of beer, potentially leading to a flat appearance and mouthfeel. When a glass is contaminated with oils, residues, or soaps—common culprits in dirty glassware—they can create nucleation sites for carbon dioxide (CO2) bubbles.

Normally, CO2 is dissolved in the beer under pressure, and as the beer is poured, it should maintain its carbonation while releasing some gas slowly. However, with dirty glassware that has these unwanted residues, CO2 can come out of solution too quickly, leading to an excessive initial release of bubbles. This rapid release reduces the amount of CO2 that remains dissolved in the beer, making it seem flat as a result of a diminished effervescence.

Additionally, when the beer is served in such a glass, the experience may not only be visually unappealing but can also affect the overall flavor as the carbonation plays a crucial role in carrying aromas and enhancing the taste profile. Therefore, cleanliness of glassware is essential to maintain the intended carbonation and overall quality of the beer served.