Water Can aid in the increase of the volume of egg white foam, but too much can decrease its stability. When whipping egg whites, use either a deep copper or stainless steel bowls. Copper contains an egg white protein which stabilizes the foam and helps the whites to retain moisture. You can use glass, but never aluminum because the egg whites will discolor, so stainless steel is good. Beaters can make a small difference in volume.
Some classicists use a large balloon whisk and a copper bowl.
I prefer to use a hand-held electric mixer. With it, I can move the beaters to reach all of the foam which gives me the best possible volume. The stand mixer can also be used, but the beaters do not quite reach the bottom of the bowl, which is a problem especially with a small amount of egg whites. Never use a blender. Degree of Beating When whipping egg whites, always start your mixer on medium-low to medium speed.