Why does pouring Champagne down the side of a tilted glass usually keep more fizz than splashing it straight into the middle?

Answer: Lower dissolved gas loss

Protective foam cap — A foam blanket sounds plausible because foam can look like it is holding gas in. But a splashy pour creates foam by forcing dissolved CO2 out of the wine, which is already a loss. The side-pour helps because it is gentler and wastes less gas before the first sip, not because it builds a protective cap.

Lower dissolved gas loss ✓ — Right: the angled pour is gentler, so less CO2 escapes during the pour itself. Liger-Belair's work found that pouring method can change how much dissolved gas is lost before the glass is served. That is a good reminder that bubbles are not just decoration; they carry aroma compounds upward and change the tasting experience.

Smaller bubble size — Smaller bubbles can feel elegant, so it is easy to connect them with longer-lasting fizz. But the tilted pour is not mainly a bubble-size machine. It preserves more fizz because it avoids shaking dissolved gas out of the wine during the pour.