We all remember how to blow soap bubbles . . . how do you make one big bubble? Blow very slowly into the wand, and the bubble grows. The force of air entering the bubble is less than the force holding the bubble on the wand, and so the bubble is not "shot forward" off the wand. Blow rapidly . . . . and the bubbles are shot forward off the wand with the force of the air projection before it has a chance to grow in size. These same principles explain how injection rate affects the size of bubbles in the eye during pneumatic retinopexy.