The jug must be large enough for the milk to expand and spin, and small enough that the wand reaches properly.
The rule
Fill to the base of the spout — roughly a third to a half full. The milk expands substantially when stretched, and it needs room to vortex.
That means a jug about twice the volume of the milk.
The sizes
350 ml — one flat white or cappuccino (around 150 ml of milk). The most useful single-drink size.
600 ml — two drinks, or one large latte.
1 litre — three or more. Unwieldy for a single drink.
Why too big is a problem
With too little milk in a large jug, the steam tip cannot submerge properly without touching the bottom. You cannot build a vortex, and you cannot texture.
This is why steaming 100 ml in a 1 litre jug never works.
Why too small is a problem
The milk expands over the rim while stretching, and there is no room for a vortex.
The spout
A sharp, well-defined spout matters for latte art — it controls the stream. Rounded spouts pour wide and vague.
Some jugs have a very narrow spout for detailed work; a moderate one is more versatile.
Material
Stainless steel, always. It conducts heat so you can feel the temperature through the wall, which is how most people judge when to stop.
Non-stick and coloured coatings interfere with that.
Last reviewed 8 August 2026