When you steam buns from leavened dough, a little soda ash takes away the sour taste.
Tips
mistakes
Three "sodas" are easy to mix up: 纯碱 or 苏打 is soda ash (Na₂CO₃), 小苏打 is baking soda (NaHCO₃), and 烧碱 is caustic soda (NaOH). Despite its name, 纯碱 is a salt, not a base.
