Matcha Foam Explained

Saponins: Matcha contains saponins (natural foaming agents) that help create foam. Surfactants are substances that reduce surface tension in the liquid so bubbles are easier to form and hold. 

Whisk: You need vigorous whisking. Whisking introduces air (gas) into the mixture, forming bubbles. More tiny bubbles means better foam.

Temperature: If water is too cool it makes particles clump, slows down surfactant extraction, etc. Around 158 °F seems optimal in many studies for extracting surfactants while avoiding overly bitter compounds. I simply use warm water from the tap.

Ratio: The amount of matcha vs water matters (matcha concentration). Having enough powder helps both in producing foam and making it stable. Too little matcha (or too much water) = weak, short-lived foam. This is why we whisk with only a few ounces of water first, then add milk or more water to the cup.

Foam duration: Once foam is created, how long it lasts depends on bubble size and consistency (how uniform the bubbles are), the presence of matcha particles in the “membrane” of the bubbles (they reinforce the foam), and the rate at which water drains out of the foam. Smaller bubbles mean less drainage, more stability. Larger bubbles tend to collapse or merge.