The title says it all...almost.

I was preparing a warm (90-100F) mixture of tap water, EV olive oil, and leaf lard (each about 50-60g). At first, the oil and water were added and brought to said temperature. Then, I added the leaf lard from a bag, squeezed out the end - similar to past from a tube/bottle. Perhaps that's too much detail there but just mentioning it JIC. Upon the lard reaching the somewhat warmed water-oil solution, it started popping in basically the same way that high-temperature oils do when water is added at frying temperatures.

What chemical/physical process is facilitating this phenomenon?

  • 1
    I find the whole description very puzzling. If you happen to replicate the whole thing, maybe you can post a video of it?
    – rumtscho
    May 16, 2022 at 11:16
  • Indeed. I agree, @rumtscho. I'll find some time this week to replicate this scenario again, record, and then post a (youtube) link here. Apologies for not supplying that context with this post.
    – nate
    May 16, 2022 at 12:07

1 Answer 1


Oil heats up faster than water. Water being more dense sinks. When it reaches the boiling point, steam has no where else to go. That's the typical experience, but also consider that water can evaporate at a temperature lower than the boiling point. So, as your initial mixture was heating, the layer of oil on top was protecting steam from escaping. When you dumped in the leaf lard, you broke the surface and added more moisture (which is likely contained in the leaf lard). The escaping steam caused the popping. The physics here is the difference in heat capacity of oils and water, the density of the materials, and the temperature at which liquids evaporate.

  • This was my first thought too, but on a second look, the whole seems more mysterious. 1. The lard was colder than the watery mixture and the "explosions" started immediately when the lard touched the water - so it was not a case of water being heated rapidly by fat hotter than itself. 2. The OP said "90-100F", not celsius - this is body-warm, at that temperature the water is nowhere near becoming steam.
    – rumtscho
    May 15, 2022 at 7:32
  • @rumtscho for now, I am sticking with my theory. The water/oil mixture was warmer than the OP assumed, and the leaf lard contained additional moisture. I'll amend my answer a bit.
    – moscafj
    May 15, 2022 at 10:36
  • Yeah OP does not state that they were stirring the mixture, while being rather specific in their description as a whole. This makes the most sense. Especially if the temperature probe was only applied to the oil (If that even happened)
    – SirHawrk
    May 31, 2022 at 9:06

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