Foundational
Milk steaming and texturing
How steaming milk works, and why texture differs between drinks like cappuccino, latte and flat white.
What steaming does
A steam wand introduces both heat and air into milk. Air introduced early in the process (while the milk is still cold) creates foam; once the desired foam volume is reached, the wand is positioned to heat the milk further without adding more air.
Why texture varies by drink
A cappuccino uses more air for a thick foam layer; a flat white and latte use less air for a smoother, denser microfoam; a cortado uses milk that is warmed with minimal foam at all.
Common problems
Milk that will not foam is often too warm already, or the wand tip is submerged too deep. Milk that is overly bubbly with large bubbles usually means air was introduced too aggressively or for too long.
Overheating, splitting and hygiene
Milk heated much past roughly 65-70°C can scald, giving a flatter, less sweet taste and a thinner, less stable foam — a light sweetness some tasters notice in well-steamed milk comes from heat gently breaking down lactose, which overheating pushes too far. Milk heated too far or held too long can also split (the fat and liquid visibly separating), which is not recoverable. Separately, the steam wand itself should be purged and wiped after every use — dried milk residue inside the wand tip is both a hygiene issue and a common cause of inconsistent foam on the next drink.
Plant-based milks and allergen care
Beyond foam behaviour (see milk science), plant-based alternatives carry their own allergen and dietary considerations distinct from dairy — oat, soy, almond and other bases each have a different allergen profile, and cross-contact between milk types is a real concern for anyone with a genuine allergy, not just a taste preference. If serving someone with a stated allergy or intolerance, use a dedicated jug and wand-purge routine for that order rather than assuming a quick rinse is sufficient. This is general food-safety practice, not medical advice — anyone managing a diagnosed allergy should follow guidance from their own healthcare provider, not this page.