i have read in various articles that when frothing milk for a cappuccino, the milk should double in volume at the end of it.
using my breville dual boiler, when i steam for 2 cups, my volume doesn't increase anywhere near doubling. the only time when it does is when i've way over frothed the milk.
does my technique need work or is the rule of thumb a little off?
I concur with Joe. Double volume does sound a lot. However, if someone asks me for lots of froth on their coffee, I ensure the frothing nozzle is more "out" than "in" the milk vortex. This gives me loads of bubbles, which is what they want. But myself, if I ask for a cappo, I only like about 1/2 inch of froth on top, and it has to be silked and textured so fine. No big "bubbles" for me!
Double the volume is too much. It should only increase approximately 20% and you dont want bubbles just silky foam.