Milk can tame a bitter espresso and round out its flavor, but lots of new baristas end up with hot milk or with a cappuccino that is all foam and won’t hold the dry bubbles together. The term microfoam refers to bubbles that are so small they shine like liquid and pour and hold like paint. Creating microfoam has little to do with power, but everything to do with the placement of the steam wand, and listening. You want to push in a little air at the outset and then merely warm and fold the rest in.
Start with cold milk in a cold pitcher. Hold the tip just below the surface but close to the edge. Turn on the steam; as it begins to flow, slowly tilt the pitcher down until you hear a slight tearing sound or the sound of paper ripping, meaning that the air is entering the milk in a gentle fashion. After a few seconds, move the pitcher up again so that the tip is lower in the milk and creating a whirlpool effect, which will break the big bubbles into tiny ones and heat the milk evenly. If all you hear is a loud hissing, the tip is too close to the surface; if the milk screams, it is probably too low in the pitcher.
It’s common to over-aerate the milk, resulting in a dense foam that floats on the surface of the milk rather than integrating. You should end the air-intake when the pitcher is warm to the touch. Then, you should only agitate the milk in a whirlpool pattern until the pitcher is hot, but still manageable to hold for a few seconds. The reason you don’t want to over-heat is because it kills all the sweetness in the milk and it also ruins the microfoam structure. Tapping the pitcher on the counter and then swirling it out should break any remaining bubbles on the surface of the milk and smooth the microfoam.
Practise briefly with water and a drop of dish soap to mimic the consistency of milk, so you can repeat the exercise without pouring the contents away. For a few minutes just practice making the noise; afterwards, practice releasing air to the roll. With milk, test the results by pouring a little into a cup and seeing how it settles; well-textured milk should appear shiny and smooth, not bubbly or layered. The more you repeat this, the more your hands will learn to do it for you.
If still your pour leaves a white ball, rather than a crema surface, this is almost always a temperature or foam density issue, not a pouring one. Milk that’s too airy won’t meld with the espresso, and milk that’s too hot will have lost its sweetness and texture. Tinkering with when you first aerate should eliminate either issue. As you get into a daily routine, you’ll start to hear the difference between a banging steam sound and a controlled hiss, and you’ll taste the difference between a silky cup that seems to happen by chance, and one that’s intentional.