Recipes using butter as a fat to sauté sometimes call for you to wait until the foaming has subsided. What causes the foaming? Why do you wait for it to subside? What's the difference if you don't wait, but just melt the butter and press forward?

1 Answer 1


The foaming is caused by the water in the butter boiling away. The main reason you wait for it to subside is simply because that means the butter has had long enough to reach a proper temperature for cooking: too cold and the food will absorb the butter rather than fry in it. However, this usually applies more to recipes that require relatively fast cooking. You'd sweat onions or scramble eggs when the foaming starts, for example.

  • That's what I figured. Any idea what the temperature swing is pre / post water boiling out?
    – yossarian
    Jun 5, 2011 at 19:51
  • 2
    Well, the water obviously boils at 100C. The fat starts to brown at 150C. I'd imagine there's a fairly smooth gradient between the two. Jun 5, 2011 at 20:00
  • 1
    While the water is boiling off, the energy (from the burner) is going to that, so the temperature is fairly constant. Once the water is gone, the temperature quickly rises. Similar to what happens if you boil a pan dry; as long as there is water, it'll be at ≈100°C, but once that water is gone, the pan will fairly quickly heat up. In other words, keep an eye on the butter!
    – derobert
    Jun 6, 2011 at 20:49

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