Sugar

Sugar both hinders and helps foam making. Added early in the process, it delays foaming, and it reduces the foam’s ultimate volume and lightness. The delay comes from sugar’s interference with the unfolding and bonding of the proteins. And the reduction in volume and lightness is caused by the syrupy sugar-egg mixture being harder to spread into thin bubble walls. Slow foaming is a real disadvantage when the whites are whipped by hand—at standard soft-meringue levels, it doubles the work—but less so if you’re using a stand mixer.