@Sneftel The heat is stored as pressure, and some is lost through the walls, unless the safety valve opens! I edited the answer to make it more complete and hopefully more clear. It is pretty obvious that it would be very hard to reach a rolling boil. The subject is taught in the regular coursework for chemistry and chemical engineering, four times - general chemistry, p-chem, thermodynamics and statistical mechanics in grad school..

And when the pot reaches full pressure and the release valve start venting steam? The boiling is depressed to what can vent but it is still boiling. The pressure can not build indefinitely to the point of equilibrium- that would just be a bomb. In an instant pot the temperature is controlled to allow an equilibrium at a target temperature (and thus pressure) without venting but this is not a normal pressure cooker.

So, I suppose your answer is correct that it will reach equilibrium without boiling only in an instant pot- not because the pressure will keep building- but because the pot will control the temperature and apply less energy when it reaches equilibrium.

@sobachatina Your first comment is true in so far as venting will let it boil more (or a little). But (a) the OP asked about a "rolling boil", and (b) you are trying to make a quantitative argument without having the numbers on which to base it. We don't how big is the pot, how much it vents, or the several numbers that go into losses through the walls. Don't forget also that at equilibrium there is no net increase in temperature or pressure.

@sobachatina I wrote that it will be hard to reach a "rolling boil" and that boiling will be self limited, or suppressed if you like. I did not say that it will not boil at all.

If you are defining rolling boil as a boil with no back pressure then your argument is a tautology. I think we've come to an agreement of terms though. We are both saying that for (not an instant pot) pressure cooker at full pressure will boil. We seem to be implicitly disagreeing about how vigorous of a boil constitutes a "rolling boil" which probably doesn't matter.

@sobachatina No, again, rolling boil means a fast boil with production of bubbles of sufficient size and rate as to disturb the surface in a certain recognizable way. It is not at all clear that it will even boil in all cases. For example, it is easy to conceive of a case where it might approach boiling but never get there.

I do think you should edit the answer a bit to be specific to the question. The question was if an instant pot will boil vigorously enough to bath meat in liquid which is a resounding "no"- not because of infinitely increasing pressure but because the instant pot will stop heating as vigorously.

@DrM I assume you have used a pressure cooker? There is a weight to regulate pressure through a small orifice. You know it's at pressure because the steam lifts the weight and vents. It can be quite violent if you don't turn the stove down. I will agree with you that it's hard to observe how vigorous the motion of the water is inside but it is definitely boiling.

@sobachatina Read it again. The part you refer to is labelled "background". The question specifically asks whether it will maintain a "rolling boil". Read my answer again too, it is very specific and speaks to exactly what was asked. Boiling has to work against the build-up in pressure, and rolling boil will be even harder to reach.

I feel like I've reached a consensus with you in the comments.

You are answering a different question than I would but that's your call of course.

I am answering what he asked, verbatim. The background is not the question, and besides that it is not a well formed question even if it were to be asked.

Right, referring to the second part of your last comment. You need details, its not a reasonable question as asked.

He asked "do those liquids continue that "rolling boil" once the cooker is up to full pressure? Or does the increase in pressure keep the liquids from continuing to actively boil?"

That's very clear, and that is what I answered, apart from knowing what pressure the valve is set for and what temperature he is driving it to.

That's fair.

You must admit that the background changes the question though.

Your answer goes from "It will be difficult" to "no and instant pot will never boil vigorously"

For a regular pressure cooker, if I leave the stove full on, and the regulator is dancing as much as it will, I wonder whether the liquid inside is moving enough to baste meat.

Thank you. I don;t know, people ask ill formed questions all the time. I am used to it. I think it will be difficult to reach a vigorous boil.

I wonder if I could use dyed liquid and something to catch splattering and see how far up the splatter would reach in a regular pressure cooker.

Seems like the steam would make it hard to capture any results.

It is easy to work out. It is the known pressure and temperature curve for boiling water. For a given weight on the vale, you need to be able to get to that temperature, with some head room to drive it harder into a full rolling boil.

Probably it can be done with a light enough weight. After all, with no weight at all, it becomes easy.

No weight at all is still some pressure. I'm more concerned about finding a material to registers splattering that won't have the results messed up by the chamber full of steam.

Okay, good, you have an experiment. Don't forget surface tension. It will be different with salt, oil, even sugar and certainly with soap.

I suppose I'll just try it and see what problems I have.

I'll try to remember not to baste meat with soap. :)

great. Okay, I have some actual science to do also. see ya