A Barista's Crash Course in Steaming Milk
"I can sit across the room from a barista and tell exactly what texture will appear just by the sound of the aerating milk."
After last week's post, "What Is Your Idea of the Perfect Cappuccino?," I was happy to see a bulk of readers interested in learning more on creating beautiful milk texture. Creating this steamed milk known as microfoam—a liquid foam with invisible air bubbles called grain—starts with one important and powerful ingredient: pressure.
A commercial espresso machine, such as the multiple boiler La Marzocco GB5, which I find myself working on in the wee hours of the morning, allows me the ability to activate the necessary amount of pressure to achieve my texture goals. Most home espresso machines (under about $8,000) aren't equipped with this feature, which makes it extremely difficult (to nearly impossible) to produce the optimal texture. This is one of the many reasons small artisan cafes are so popular: We leave it to the professionals.
When it comes to milk aeration you must rely on your senses. Sight, sound, and touch are all key players when steaming milk. I can sit across the room from a barista and tell exactly what texture will appear just by the sound of the aerating milk. A low, calm, rumbling noise is best for texturizing. I imagine it to sound like being underwater in a whirlpool hot tub.
So let's begin! Here are a few steps to steaming milk, accompanied by a short video of the process, after the jump.
Step One: Start with Cold Milk
Make sure you have cold milk and an even colder pitcher. This low starting temperature allows a longer steaming window, which provides optimal texture. When pouring this cold milk into the pitcher it should come right to the bottom of the pour spout; too much milk gives you no room to move, and too little milk leaves you with no window at all. Remember, even if you only need two ounces of microfoam, you'll need at least four ounces of milk to get it.
Step Two: Watch, Listen, and Feel
Submerge the wand and active steam pressure. Then instantly and with control, gently pull down on the pitcher, watch the wand appear slightly, listen for a slight crackle noise (this is aeration), and feel the temperature increase with the palm of your hand.
Step Three: The Rolling Effect
Tilt the pitcher and look for a swirling motion known at the rolling effect. This appears almost like water being pulled forcefully down a drain. The lowest point of this swirling motion is called the vortex. You should hear the low rumbling noise described earlier—this is what makes texture. After you feel the pitcher reach 150 to 160 degrees, or when you can't hold your palm to the pitcher for more than a fraction of a second, turn off the steam pressure. If you heat the milk much beyond this point you run the risk of ruining your beautiful texture or burning the contents.
As you swirl your final product in your pitcher, it should appear smooth with a glossy shine—a chiffon of microfoam to fold beautifully into the espresso, utilizing the crema as the background for your latte art.
About the Author: Erin Hulbert, a native Seattleite, has been in the coffee world for well over a decade working with and learning from some of the most influential coffee minds in the industry. She now lives in the West Village in New York City, where she teaches, consults, and recently finished her first book Finding the Grind: A Barista Guide, due out this year. She also can be found pouring lattes as one of three trainers at Joe on Waverly Place. Read more from Erin at her blog Finding the Grind.