Step 3: Now- back and forth and back and forth.
Put your towel or potholder on the top to protect your hand from the heat. Hold firmly at the top and start slowly pumping the knob up and down.
Hold on tightly- HOT HOT HOT!
Normally, a minute or two of pumping is sufficient to create a super-dense and velvety foam. The milk will approximately double in volume during foaming.