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Cooks sometimes use the Leidenfrost effect to estimate the temperature of a frying pan by flicking a few drops of water onto the heated pan. I had no idea, before looking into this, that this could be such a rough estimate.

One site I looked at has the Leidenfrost point for water at 482°F (250ºC).

The Wikipedia article (without citation) places the temperature that this happens around 193ºC, but also notes that the estimate is quite rough,

The temperature at which the Leidenfrost effect begins to occur is not easy to predict. Even if the volume of the drop of liquid stays the same, the Leidenfrost point may be quite different, with a complicated dependence on the properties of the surface, as well as any impurities in the liquid [...] As a very rough estimate, the Leidenfrost point for a drop of water on a frying pan might occur at 193 °C (379 °F)

When estimates differ by more than 50ºC, that really is pretty rough (from a cooks perspective at least).

My first question is whether it is correct that the Leidenfrost point for water really is so difficult to pin down?

And secondly, is there anything cooks can reasonably do to improve this technique in terms of recipe repeatability?

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I'm not that much of a science guy, but I'm thinking it would be real difficult for a cook to pin that temperature down. There are just too many variables I can think of that would influence when the Leidenfrost effect would start to occur and how long the droplet will last.

  • Temperature of the pan.
  • Surface texture of the pan.
  • Material of the pan (thermal conductivity wise).
  • Temperature of the droplet.
  • Density of the droplet.
  • Amount of liquid in the droplet.
  • Properties of the droplet (thermal conductivity wise).
  • Atmospheric pressure.
  • Velocity at which the droplet is thrown in.
  • Angle at which the droplet is thrown in.

And these are just the ones I'm thinking of, not to mention if I actually was a science guy.

If I could try to give your questions an answer, I would have to say that the temperature of the heated pan at which the Leidenfrost effect would begin to occur could be pinned down exactly if every other variable was fixed. For cooks this would be rather difficult.

But to narrow the range down a bit for home cooking use, you could get a pipette which produces an consistent droplet, and drop it at a set height from the pan. And, of course, keep using the same frying pan (also keeping its surface undamaged). As a consistent droplet source you could use bottled water. This will not tell you the temperature of your frying pan but can be used as an indicator when the temperature reaches a certain point.

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