In brief
Microfoam is steamed milk whose air bubbles are so small you cannot see them. Instead of a dry froth sitting on top, the milk turns glossy and slightly thick. Wikipedia compares it to melted marshmallows or wet paint.
The 2M Barista Journal defines it as milk with bubbles smaller than 0.1 mm, evenly spread through the pitcher. That even, fine structure is what lets it pour in a smooth stream and hold a pattern.
It is the milk behind a latte, a flat white and latte art. The opposite is macrofoam: big, stiff bubbles, like the thick cap on a traditional cappuccino.
On this page · 6 sections
How is microfoam made?
With a steam wand, in two stages. Wikipedia describes the first stage as holding only the wand tip at the surface to draw in air, for under 10 seconds. The second stage lowers the wand to spin the milk in a vortex, which breaks big bubbles into small ones.
The 2M Barista Journal puts the air-drawing phase at the first 3 to 5 seconds. You hear a short hiss as the tip pulls air in. After that, the job is mixing and heating, not adding more air.
How much air you add depends on the drink. 2M suggests a 20 to 40% rise in volume for a latte or flat white. For a classic cappuccino, it suggests 50 to 80%.
Why does milk foam at all?
Because of its proteins. The 2M Barista Journal explains that milk protein is about 80% casein and 20% whey. When steam forces air in, whey proteins form a shell around each bubble and hold it in place.
Fat works against foam. 2M calls whole milk at 3.5% fat "the standard compromise" between flavor and foam. Semi-skimmed milk at 1.5% makes a lighter foam.
What temperature should you steam milk to?
Sources differ slightly, so treat this as a range. The 2M Barista Journal calls 65 °C the upper limit for professionals. It says casein begins to denature above 70 °C and the foam starts to collapse.
Wikipedia gives a typical steaming temperature of about 70 °C, or 158 °F. It says milk heated above 82 °C, or 180 °F, scalds and will not form proper microfoam. Either way, the milk should be hot to hold but not boiling.
What is the difference between microfoam and macrofoam?
Bubble size, and what you can do with it. Microfoam's tiny bubbles stay mixed into the milk, so it pours as one liquid. Macrofoam's large bubbles float to the top and sit there as a stiff cap.
| Microfoam | Macrofoam | |
|---|---|---|
| Bubbles | Too small to see | Visible, large |
| Look | Glossy, like wet paint | Dry, stiff |
| Pours | As one smooth stream | Spooned or plopped on |
| Typical drinks | Latte, flat white | Traditional cappuccino |
Wikipedia's cappuccino article describes the traditional cappuccino as made with "a thick layer of macrofoam rather than" microfoam. A cappuccino made with microfoam is sometimes called a "wet" cappuccino, Wikipedia notes.
Why does microfoam matter for latte art?
Because patterns need a stable, pourable surface. Wikipedia says the microscopic bubbles "give definition and stability to the patterns," which are harder to achieve with macrofoam.
Timing matters. 2M notes that foam starts to separate from the milk within 30 seconds. Pouring soon after steaming is part of the technique.
Does microfoam depend on your grinder?
Not directly. Microfoam comes from the steam wand and the milk, not the coffee. But the drinks it goes into all start with an espresso shot.
The milk is poured into a shot, often onto its crema, so the drink is only as good as that shot. A sour or bitter shot is fixed at the grinder, by dialing in the espresso grind. The grinder finder narrows the options for espresso, and espresso settings by grinder has starting points for each model.
Sources
By Jeff Gluck · Checked Oct 21, 2026