Let's say you're in Atlantis, which happens to be 1 km below sea level
It's also at equilibrium with the sea. You have been born there and are fully acclimated to the pressure, in air which is made of a mixed gas with the right proportions for human life.

This is because, just like all the fictional adaptations of Atlantis, you can just swim into the submerged sea and get outside the dome. No airlocks, just equilibrium. Let's imagine their bodies have made the needed adjustments.

1km isn't as deep as you may think, elephant seals dive to more than twice this depth; there is a way. It's important to note, no one is going to the surface. This is STP as far as your little village is concerned. No pressure transitions; but that doesn't matter to the question, which is only about food processing. They are living there now, that's the point. And they want to cook. The problem of the question is this: They sit down to a nice meal and chat, or get up and make breakfast. Then I thought, "Would they smell bacon? Would grease boil? Can they talk over tea?" Hence, this question! Water boils differently. Carbonation happens differently. Maybe yeast works differently?

Some things our people would like to enjoy are listed below, and I would like to know how processing these treats would be different at 1 km below sea level, on Earth.

  • Tea and coffee
  • Buttered toast (they have vegetable margarine, actually)
  • Poached eggs
  • Cooking pasta
  • Ice cream (or similar - sherbet?)
  • Pancakes
  • Pickles
  • Fruit pie
  • grilled fish (deep seafish)
  • Turkey bacon

I believe I can derive the implications to other recipes from this representative group of culinary preparations.

All ingredients are local, nothing came down from the surface pressure.

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    $\begingroup$ I am a little confused about the setting. Are these humans in sealed underwater buildings with air? Merfolk in unsealed houses? Something else? $\endgroup$
    – Atog
    Feb 17 at 20:43
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    $\begingroup$ You are suggesting it would be liquid? This is about 93 ATM. I don't think liquid oxygen is possible at all at 25C. Here is what Quora finds. $\endgroup$
    – Vogon Poet
    Feb 17 at 21:28
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    $\begingroup$ Hyperbaric air and hyperbaric oxygen are two different things. Cooking in heliox seems plausible, but I don't know if it's been done outside of a sea monster movie. Cooking in hydroheliox ought be be interesting to watch, over a video monitor. Cooking in hyperbaric oxygen sounds like one of the world's shortest books. Though you can read a longer one. $\endgroup$ Feb 17 at 22:00
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    $\begingroup$ The critical pressure of oxygen is 49.8 atm. So above that you'd have a supercritical fluid. $\endgroup$
    – sphennings
    Feb 17 at 23:06
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    $\begingroup$ @sphennings Not possible. The critical temperature is -181.5 F, it is not possible at any pressure to liquefy oxygen above this temperature. Look for the triple point. Likewise, these numbers change in solution. From Perdue University $\endgroup$
    – Vogon Poet
    Feb 17 at 23:30

4 Answers 4


In most cases, we boil things because it is a convenient way to stop at around a certain, useful temperature, only in very few cases, that I can think of, is the act of boiling the liquid necessary for the preperation of the food. Tea and coffee are actually best brewed at slightly less than 100C: 90-98 for tea and 90-95 for coffee so this isn't a problem: take the kettle off the heat when it hits this temperature, rather than waiting for it to boil (which happens at over 300C as someone else pointed out already).

Poached eggs are also best at around that temperature, and boiled eggs are apparently best cooked even lower

With jams and pies, as well as cooking the sugar, boiling the water serves to reduce and thicken the liquid, which would happen at a massively reduced rate when the water doesn't boil, so another way would be needed to remove the water and thicken the sauce - although I don't know enough about cooking these foods to suggest one

As @Anders Sandberg poitned out in your similar question on physics stack, you would have soem issues with food where steam bubbles act to provide temperature, such as omlettes, and you would probably struggle to get a nice microfoam for your lattes. Bread might have some issues rising.

I can't think of any issues with When cooking meat or other foods, other than that the air will conduct heat a bit better at higher pressures

This is all assuming, of course, that it is possible to find a mixture of gasses that are breathable and won't explode at the first sign of an open flame!


Issue with the question: saturation diving record is only 701m, and that was stopped prematurely because they were having insomnia and fatigue issues from the depth.

We don't have any gas mix that would work for saturation diving at 1km. (Much less extended saturation diving.)

(And even that 701m figure was one diver with an mix of 49% hydrogen, 50% helium, and 1% oxygen. The rest of the divers stopped at 675m and had to go back to 650m.)

The main issue is this: every gas appears to have narcosis effects "eventually" as you increase the pressure.

Cooking in a high-pressure hydreliox mix would be weird:

  • The thermal conductivity of the atmosphere would be far higher than usual, both due to the increased density and due to the gas largely being hydrogen and helium.
  • Boiling wouldn't happen until a much higher temperature than usual. Fine for temperature-based cooking, not so fine for reductions and such.
  • The viscosity of the air is far higher than normal. (This is one of the constraints for diving mixes, actually.)
  • Many volatiles that normally boil off, wouldn't.
  • Rising agents probably just flat-out wouldn't work.
  • Beating air into a mixture may still work, but hydrogen and helium both diffuse through materials far faster than air.
  • I... honestly have no clue how burning/charring/etc would work. On the one hand, oxygen would still have a substantial partial pressure (although not too much, because that would be toxic to the diver). On the other hand, oxygen is a relatively small component of the overall mix. On the gripping hand: I have a visceral reaction to the idea of hot objects in a mix containing both oxygen and a nontrivial amount of hydrogen.

(I wasn't able to quickly find a chart of the UEL of oxygen in a hydreliox mix w.r.t. pressure, unfortunately.)

  • $\begingroup$ Good insights. I don’t think saturation diving is a fair comparison as diving involves pressure changes, these are habituated inhabitants whose entire system is already at equilibrium. And biology doesn’t pose a limit as elephant seals will dive over 2.3km without issue. But that is neither here nor there, the question is about cooking. Imagine robots are doing the cooking if needed, the human component isn’t involved in this problem. $\endgroup$
    – Vogon Poet
    Feb 19 at 22:50
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    $\begingroup$ The entire point of saturation diving is that it's slow enough that you're effectively at equilibrium... $\endgroup$
    – TLW
    Feb 20 at 4:21
  • $\begingroup$ Humans aren't elephant seals. And adaptations to high pressure would very likely affect taste and/or smell. $\endgroup$
    – TLW
    Feb 20 at 4:23
  • $\begingroup$ Your comment doesn't appear to match the question. The question tells a story of humans living at 1km depth, and asks questions like "Would they smell bacon?" and "Can they talk over tea?", both of which require humans at depth. $\endgroup$
    – TLW
    Feb 20 at 4:24
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    $\begingroup$ This isn’t a discussion. The question is bound very clearly. You may have whatever thoughts about the setting that you wish, I disagree that radically changing an organism’s pressure over a period of weeks is the same as never changing it at all. It may become a new question. $\endgroup$
    – Vogon Poet
    Feb 20 at 15:33

If you are in a sealed building at surface pressure internally, then I think cooking would work the same. If, however the pressure was higher for some reason, maybe necessary due to weaker building materials, you'd see some differences.

When at high altitudes, water boils at a lower temperature due to less air pressure. (See this wikipedia article https://en.m.wikipedia.org/wiki/High-altitude_cooking#Boiling_point_of_pure_water_at_elevated_altitudes)

I think this can be extrapolated to higher pressures, such that you may need to boil tea at 120 degrees Celsius.

Air pressure seems less relevant for other dishes, like ice cream or pickling.

  • 1
    $\begingroup$ At 101 atm (which is the pressure at 1km) water boils at more than 300C. $\endgroup$
    – sphennings
    Feb 17 at 21:19
  • $\begingroup$ No steeping of the tea then? $\endgroup$
    – Vogon Poet
    Feb 17 at 22:18
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    $\begingroup$ @VogonPoet You don't need boiling water to make tea. You just need water that is warm enough to steep the leaves. The nice thing about boiling is that it caps the temp the water can reach at 100C, at super high pressure water will get to extremely dangerous temperatures before even a hint of boiling. $\endgroup$
    – sphennings
    Feb 17 at 23:08
  • $\begingroup$ Pouring boiling water over your tea leaves at this pressure would destroy many of the tannins and chemicals making tea tea. But yes, as long as you do not add too much energy to the water, most everything should cook the same as on the surface. Poached eggs... I am not too sure how the chemistry in the egg would change at those pressures. Good thin is, freezing temperature doesnt change much so ice cream would be ok $\endgroup$
    – Sonvar
    Feb 18 at 17:39

Cooking is difficult at very high temperatures

At sea level, boiling point of water is 100 C and cooking oil is around 300-500 C.

At the depth of 1 km, pressure is 100 atm. Boiling point of water is 316 C and cooking oil is around 1200 C.

If you put an egg in boiling water at 316 C, it may be inedible in short time. Similarly, if you try to fry something in oil boiling at 1200 C, it will burn quickly.

In high altitudes, people use pressure cookers. May be you will need a sort of vacuum cooker at 1 km depth.


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