Blending hot soups and sauces

Why

When the blades start, hot liquid in a blender jar is churned violently and releases a lot of steam; if it has nowhere to go, pressure builds up in the jar, which can lift the lid and spray soup over hands and face. Manufacturers' instructions differ, though: some advise filling the jar no more than half full, preferably a third, removing the centre cap and covering the opening with a towel, others want the vented cap left in place, and some don't allow hot liquids at all or only up to a set temperature; they agree on starting at the lowest speed. Sealed smoothie cups without a vent should not be used for hot ingredients at all. An immersion blender largely avoids this risk, because the soup doesn't have to be transferred and the pot stays open; even so, take the pot off the heat. With potatoes, watch the texture too: long or fast blending releases starch from the cells and the soup turns gluey, as the Mashed potatoes card explains in more detail.

How to do it

• Let the soup stand for a few minutes after cooking and don't blend it boiling; if the blender manual gives a maximum filling temperature, keep to it.
• Fill a blender jar no more than half full, preferably a third; blend larger amounts in batches.
• Fit the lid as the manual says: remove the centre cap and cover the opening with a towel only where the manufacturer advises it; otherwise keep the vented cap in place. Always hold the lid down.
• Start on the lowest speed and only increase it gradually.
• Where possible, use an immersion blender in a pot taken off the heat; submerge the blade before switching on and lift it out only after switching off.
• Blend soups with potatoes briefly, just until smooth, or mash the potatoes instead.

If it goes wrong

If the soup starts to rise in the blender or the lid lifts, switch it off at once and don't pull the lid off abruptly; let the contents settle for a moment and open the lid away from you. Cool a scald under cool running water for 20 minutes, don't put cream or butter on it, and get help for a large, deep or facial burn. Gluey potato soup can't be made smooth again; thin it with stock and blend for less time next time.