How Does an Immersion Blender Work?

The bell does as much work as the blade

An immersion blender is a motor in a handle, a shaft, and a small blade spinning inside a bell shaped guard at the bottom. The blade alone would just push food around. What makes it work is the bell: as the blade spins it throws liquid outward, which lowers the pressure in the middle, and that pulls more food up into the blade from below. The bell is a pump as much as a shield.

That is why an immersion blender has to be submerged to work properly and why lifting it to the surface makes it splutter. It is also why you move the blender through the pot rather than expecting the pot to circulate. Braun publishes the clearest description of engineering around this in our immersion blender guide, with a POWERBell Plus bell that carries an extra milling blade to give more slices per rotation.

The bell is also the reason these machines splash. Braun publishes SPLASHcontrol technology as a named feature, and Ninja and KitchenAid both publish a pan guard, with KitchenAid describing its removable version as patented and there to protect your cookware. Those two jobs, containing the vortex and keeping the blade off a nonstick pan, are the same piece of plastic or steel doing double duty.

What the blade actually looks like

Small and close to the bottom, which is the opposite of a jug blender. KitchenAid publishes a four point stainless steel blade on a removable eight inch blending arm. Cuisinart publishes an eight inch stainless steel blending shaft. Ninja publishes a nine inch stainless steel arm with the pan guard built in. Turelar takes a different approach and publishes a two pronged blade it says cuts and purees more efficiently.

Braun publishes the most unusual arrangement in the guide: an ACTIVEBlade flexible shaft that moves the blade up and down while it spins, which the listing says gives 250% more active cutting surface. Whether that figure means anything is not something this page can check, because no listing publishes a blending result you could compare, but the mechanism is at least a real difference rather than a coating.

Shaft length is the specification that decides where you can use it. An eight inch arm reaches into a saucepan; a nine inch one reaches into a stockpot. KOIOS publishes the other half of that problem, stating that its shaft fits most pots, mason jars and wide mouth cups, because a shaft that is too wide will not go into a jar at all.

Speed control matters more here than on a jug blender

With a jug blender you set a speed and walk away. With an immersion blender your hand is the only thing holding the position, so speed control is really splash control. The guide covers four different approaches. Turelar publishes 2 speeds on a 400W motor. Ninja publishes 4 speeds. KOIOS publishes 12 speeds plus a turbo boost on a 1000W all copper motor.

Cuisinart and KitchenAid both go variable rather than stepped, Cuisinart with a slide control and a push button for continuous action, KitchenAid with a trigger switch. Braun goes furthest and removes settings altogether: its Easy SmartSpeed responds to how hard you press, so the speed is in your finger rather than on a dial.

What the low end is for is the part people miss. KOIOS spells it out, stating that low speeds fold whipped cream without deflating it. Starting slow and low in the pot, then bringing the speed up once the blade is buried, is the technique that keeps soup off the ceiling, and a machine with two speeds gives you much less room to do it than one with twelve.

Torque, stalling and thick mixtures

An immersion blender stalls when the food is thicker than the motor can turn the blade through, and two machines in our guide publish a feature aimed at exactly that. Ninja publishes SmartTorque, which it says maintains a consistent speed with thick and frozen ingredients. KOIOS publishes overheat protection and anti-stall power, and says its 1000W copper motor dissipates heat faster.

The other listings are honest about the limit in a different way. Bonsenkitchen publishes an explicit instruction not to process hard, frozen or fibrous ingredients, which is a clearer statement of the same boundary than any torque claim. Cuisinart and Bonsenkitchen both publish a 300-watt motor and turelar publishes 400W, so the spread across the guide runs from three hundred watts to a thousand.

Weight is worth reading alongside power, because you hold this machine. Turelar publishes 1.45 pounds, KitchenAid 2.03, Braun 2.2, KOIOS 3.26 and Cuisinart 3.31. Blending a full pot of soup with a three pound machine at arm’s length is a different experience from doing it with a pound and a half, and no listing mentions that trade.

The published dimensions, and one that cannot be right

Overall height tells you how much drawer or cupboard you need: Cuisinart publishes 15.5 in, Ninja 15.95 in and KitchenAid 16.3 in for the full assembled tool, while the shorter units in the guide publish 8.5 in, 9.25 in and 9.83 in for what is usually the motor body alone.

One set of figures in the guide does not work. Braun’s listing publishes 43.31 in by 5.12 in by 59.06 in, which describes no hand blender ever made, and its published weight of 2.2 lb makes the dimensions even less believable. That is a listing data error rather than a product problem, and nothing on this page is built on those numbers.

The last thing worth knowing is cleaning, because it is where the design shows. Most of these come apart: KOIOS publishes one click release attachments that are dishwasher safe except the motor, KitchenAid publishes a dishwasher safe blender arm, and turelar publishes a warning that the electronic and plastic part must not be washed in water at all. The usual trick, running the blender in a cup of warm soapy water, is published by KOIOS as the maker’s own advice.