# My pressure cooker takes too long to cook the grained rice



## Josue

Hi, we call that "arroz graneado" in spanish.
Anyway, my problem is that I think my cooker takes too long to cook it, about 15 minutes. In every video on YouTube they say it takes about 5 minutes, I don't understand why my cooker takes too much, it's a new cooker.
The way I cook the rice is like this: I put water on the cooker and (of course) light the fire, at the same time I start to roast the rice and when it is done I open the cooker and put it, when the cooker starts to boil hard I start counting 15 minutes and then put out the kitchen fire and wait until the steams stop going out and that also takes about 15 minutes, that seems too much time, because as I said I heard it takes just 5 minutes to cook and then they put out the fire.
My question to you is: how much does it take it to you? What brand of pressure cooker do you use?
I put a image of my cooker. I hope very much your answers.


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## CraigC

Why do you want to cook rice in a pressure cooker? We tried a rice cooker once without satisfaction, so we still cook our rice on the stove top with out issue.


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## Addie

CraigC said:


> Why do you want to cook rice in a pressure cooker? We tried a rice cooker once without satisfaction, so we still cook our rice on the stove top with out issue.



Same here Craig. It only takes 20 minutes. With her waiting for the pressure to drop to a safe level, it is taking her twice as long. 

I had a pressure cooker back in the late 60's. I remember very well, it said to not cook grains in it. The directions said that it is possible for a grain to  clogged the steam outlet and the pressure can build up. Maybe they have made them safer today.


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## CraigC

We use the pressure cooker I got when my oldest brother passed.


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## medtran49

Addie said:


> Same here Craig. It only takes 20 minutes. With her waiting for the pressure to drop to a safe level, it is taking her twice as long.
> 
> I had a pressure cooker back in the late 60's. I remember very well, it said to not cook grains in it. The directions said that it is possible for a grain to clogged the steam outlet and the pressure can build up. Maybe they have made them safer today.


 
Grain can be cooked in a pressure cooker but you have to follow the directions of not over-filling so that it could potentially clog, and also you need to make sure the vent/pressure hole in the middle of the top is clear, as well as the safety release valve both BEFORE and AFTER cooking.  

Given that I am still _extremely_ wary of using one after what I witnessed as a child of the aftermath of over-filling and blocking the pressure vent hole, the pressure cooker is definitely 1 utensil that I follow *EXACTLY TO THE LETTER* the instructions on using.


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## callmaker60

It only takes 20 minutes on the stove.


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## Josue

Thank you very much for your answers.
I want to cook it on the pressure cooker because I want the meal to be ready soon. Buy I still have the question, do you use to cook grained rice on pressure cooker? if you do, how much does it take to you? and what brand of pressure cooker do you use?


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## Josue

By the way, it seems somebody misunderstood my name! I am a MAN not a WOMAN.


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## GotGarlic

I've never used the pressure cooker to make rice. As has been said, it takes 20 minutes on the stove. Once it's done, you can take it off the heat and keep it covered and it will stay warm until you're ready to eat. Time the rest of your meal to coincide with the rice and you're good to go


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## Andy M.

What do the pressure cooker instructions say about cooking rice?  You did read the instructions, right?


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## Addie

GotGarlic said:


> I've never used the pressure cooker to make rice. As has been said, it takes 20 minutes on the stove. Once it's done, you can take it off the heat and keep it covered and it will stay warm until you're ready to eat. Time the rest of your meal to coincide with the rice and you're good to go



Good advice. If you cook the rice in 20 minutes on the stove top, you can then use your pressure cooker for a different part of the meal. Like your vegetables, or even braised meat. You can cook a chuck roast in less than 30 minutes So in the time it takes for the meat to cook your rice can be done at the same time.


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## Josue

Andy M. said:


> What do the pressure cooker instructions say about cooking rice?  You did read the instructions, right?


Well, my cooker doesn't have instructions about any meal, it just says thinks about safety, how to handle the little parts of it and so on.


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## Andy M.

Josue said:


> Well, my cooker doesn't have instructions about any meal, it just says thinks about safety, how to handle the little parts of it and so on.



Does it cook other foods properly?  If not, there may be an issue with the pressure cooker.


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## GotGarlic

Josue said:


> ... when the cooker starts to boil hard I start counting 15 minutes and then put out the kitchen fire and wait until the steams stop going out and that also takes about 15 minutes, that seems too much time, because as I said I heard it takes just 5 minutes to cook and then they put out the fire.



If the recipe/video you're following says to cook for 5 minutes and then put out the fire, why are you cooking it for 15 minutes?


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## Josue

GotGarlic said:


> If the recipe/video you're following says to cook for 5 minutes and then put out the fire, why are you cooking it for 15 minutes?


I do it because the rice is still raw if I put the fire out at five minutes.


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## Josue

Andy M. said:


> Does it cook other foods properly?  If not, there may be an issue with the pressure cooker.


Honestly I didn't try it, I bought the cooker to make grained rice. I can try to cook fried chicken meat, how much should I have to wait for it to be cooked?


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## GotGarlic

Josue said:


> I do it because the rice is still raw if I put the fire out at five minutes.



In that case, I'd call the recipe a failure and stop trying to make it.  Even if it did cook in 5 minutes, you still have to wait 15 minutes for the pressure to diminish, which is the same amount of time it takes to make rice in a regular saucepan.

Not every Internet recipe writer knows what they're doing.


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## Chief Longwind Of The North

I cook rice for about seven minutes in my pressure cooker and it comes out perfect.  The rule is to add 3/4 cu of water for every cup of rice.  Place on the stove over medium high heat until the regulator just starts rocking.  You then know that you are at the correct internal pressure.  Also, never fill the pot over 2/3rds full, with anything.  If you are cooking starchy foods that will create foam when boiling (like rice) add a little butter, or oil to reduce or eliminate the foaming.  After the correct time has elapsed, place the pressure cooker into your sink and run cold water over the top.  This will reduce the pressure in seconds until the safety button releases, at which time you can remove the regulator to allow even more steam to escape and equalize the pressure inside and out.

My pressure cooker develops 11.5 pounds of pressure, which raises the temperature required to bring water to a boil, which in turn works with the steam and pressure to quickly cook the food.

Remember, if you are using brown rice, or wild rice, these take a longer time to cook than does white rice.

Seeeeeeya; Chief Longwind of the North


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## roadfix

Josue said:


> By the way, it seems somebody misunderstood my name! I am a MAN not a WOMAN.



Americans mistake your name for Josie.... We see the first and last letters of a word and everything in between is just a blur...


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## roadfix

If it's not cooking fast enough perhaps it has a bad seal.


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## GotGarlic

Chief Longwind Of The North said:


> I cook rice for about seven minutes in my pressure cooker and it comes out perfect. ... After the correct time has elapsed, place the pressure cooker into your sink and run cold water over the top.  This will reduce the pressure in seconds until the safety button releases...



This seems like a lot of extra work for a small savings in time, not to mention using extra water unnecessarily. What is the advantage over cooking it in a saucepan? I don't see the problem with waiting 20 minutes for rice to cook.


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## medtran49

Um, I just looked up Oruro, it's *over 12,000 feet above sea level*.  So, if that's where Josue is, then that explains why it takes so long to cook.

Josue, if Oruro is, indeed, where you are from, you need to look for recipes specifically for high altitudes and/or ask for help from a neighbor or family member since I'm assuming you haven't been cooking for long since you are on this board asking for help for such a simple dish as rice.


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## GotGarlic

Wow. Yes, that would do it. Good thinking, medtran.


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## roadfix

At at altitude your pressure cooker will take about 30% longer to cook....


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## RPCookin

GotGarlic said:


> I've never used the pressure cooker to make rice. As has been said, it takes 20 minutes on the stove. Once it's done, you can take it off the heat and keep it covered and it will stay warm until you're ready to eat. Time the rest of your meal to coincide with the rice and you're good to go



At altitude (I'm at 4000 feet above sea level) it takes more like 30 minutes to cook white rice.  I mostly use brown rice, and that takes more than an hour, and about half again as much water as white rice.



roadfix said:


> At at altitude your pressure cooker will take about 30% longer to cook....



Why?  The point of the pressure cooker is to create a higher pressure in the cooker.  Just because the ambient pressure is less, does the pressure cooker pressurize less too?  I don't understand why that would be.  I'm asking because I've never owned one - never felt a need for it.


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## GotGarlic

RPCookin said:


> At altitude (I'm at 4000 feet above sea level) it takes more like 30 minutes to cook white rice.  I mostly use brown rice, and that takes more than an hour, and about half again as much water as white rice.



That makes sense. It didn't occur to me.


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## taxlady

RPCookin said:


> At altitude (I'm at 4000 feet above sea level) it takes more like 30 minutes to cook white rice.  I mostly use brown rice, and that takes more than an hour, and about half again as much water as white rice.
> 
> 
> 
> Why?  The point of the pressure cooker is to create a higher pressure in the cooker.  Just because the ambient pressure is less, does the pressure cooker pressurize less too?  I don't understand why that would be.  I'm asking because I've never owned one - never felt a need for it.


I imagine it takes longer to get it up to pressure.


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## Selkie

RPCookin said: "*The point of the pressure cooker is to create a higher pressure in the  cooker.  Just because the ambient pressure is less, does the pressure  cooker pressurize less too?*"
Yes. The pressure relief valve (the part that goes Hssssss...." relieves the pressure differential between the inside and outside of the pressure cooker. If it's set for 10 pounds (just an example), it will release the pressure 10 p.s.i. above the ambient pressure, no matter what the local pressure is.
In short, local altitude does matter.


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## roadfix

If you can regulate (increase) the pressure in the cooker (adjustable pressure relief valve) you can compensate and cut the cooking time at altitude.


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## RPCookin

The only pressure cooker I've ever seen in action was my mother's.  It was an old Presto (had to be pre 1950), and the relief valve was nothing more than a hole in a stem in the center of the lid, and you  used a weighted plug sort of thing that just rested on top of the stem.  It was the weight of that plug which regulated the pressure, and when the cooking was over, you just took that off and it depressurized through the relief hole in a few seconds.  

That one would have cooked to the same internal pressure no matter the ambient atmospheric pressure because it was controlled by gravity.


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## Chief Longwind Of The North

Selkie said:


> RPCookin said: "*The point of the pressure cooker is to create a higher pressure in the cooker. Just because the ambient pressure is less, does the pressure cooker pressurize less too?*"
> Yes. The pressure relief valve (the part that goes Hssssss...." relieves the pressure differential between the inside and outside of the pressure cooker. If it's set for 10 pounds (just an example), it will release the pressure 10 p.s.i. above the ambient pressure, no matter what the local pressure is.
> In short, local altitude does matter.


 
What you say could be correct, if the pressure exerted by the outside ambient pressure determined the force placed on the pressure regulator. But at least in both of my pressure cookers, there are weights that regulate the pressure. It takes 11.5 lbs. psi to lift the weight of the regulator to allow steam to escape. My larger Pc has added weight rings that can be added so that the internal pressure of the pot requires 11.5, 12, or 15 lbs. of internal pressure to release steam, regardless of the ambient atmospheric pressure. The deciding factors are the rigid, closed pot, and the weighted pressure regulator. The inside conditions of the pressure cooker are isolated from outside conditions except for gravity. If you were on the moon, it would take much less pressure to cause the PC to release pressure, but that is because the regulator would weigh less due to a weaker gravitational field, not because the PC is in a vacuum.

If the PC were a semi-flexible container, then yes, outside pressure would make a dramatic difference.

Water boils at a lower temperature in an unsealed pot because there is less atmospheric pressure. But the PC develops its pressure by lifting a weight. The difference in the weight of the regulator between 5000 feet, and sea level is negligable, and so the internal pressure of the pot should be the same regardless of the elevation you are cooking at. 

I concur with the post that suggests a poor seal between the lid and the pot, or maybe a faulty pressure valve, if your PC has one.

In answere to GG's question, I sometimes cook my rice on the stove top, in a covered pot, sometimes in the rice cooker, and sometimes in the PC, depending on other factors. The PC is not any more work than the other methods, and shortens the cooking time required, which can free me to get other things done, as that burner is available to me for reuse sooner.

Why, I've even been known to pre-cook my rice, and heat in later in the microwave.

There are valid reasons to use the PC, just as there are valid reasons to cook a specific rice pilaf that we make on the stove top rather than in the oven, in a casserole dish as the recipe was first given to us. Sometimes though, using the casserole dish is the better choice, again, depending on other factors. And the cookinhg period from removing the PC to opening the lid, when I place the unopened PC under cold running water is less than 30 seconds, litteraly.

To know many techniques is to allow greater creativity, and better time management. It gives you flexibility.

Oh, one thing that will affect time is outside ambient temperature. The cooler it is in your home, the more time that will be required to bring the PC up to sufficient temperature to develop the required cooking pressure, and more energy will be required to keep it there. The pot radiates heat, as well as absorbing it. The greater the difference between the temperature of the metal, and the air, the faster the pot will radiate heat from the pot.

Seeeeeeeya; Chief Longwind of the North


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## roadfix

RPC.......But if the ambient pressure is lower then there is less pressure "weighing" that plug down against the relief hole, I would think....


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## Chief Longwind Of The North

roadfix said:


> RPC.......But if the ambient pressure is lower then there is less pressure "weighing" that plug down against the relief hole, I would think....


 
The size of that plug wouldn't create enough pressure difference to cause dramatic change.

If you have a container whose lid is say, 100 square inches in size, then if you pump 15 lbs of pressure into the container, the lifting pressure on the lid would be 100, times 15, or 1,500 psi.  The average pressure regulator probably has less that a squate inch of area on which the atmospher can exert force.  Let's say we have an average atmospheric pressure of 10 lbs. per square inch, and the regulator has an area of .5 inches.  The pressure exerted on the regulator is 5 lbs. psi, and it is exerted on top, on the sides, and underneath the reculator, and so has virtually no affect on the pressure regulator.  The inside temperature however, exerts its energy in one direction, to lift the regulator upward.  It has no force to counter that lift except gravity.

Seeeeeeeya; Chief Longwind of the North


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## Josue

GotGarlic said:


> In that case, I'd call the recipe a failure and stop trying to make it.  Even if it did cook in 5 minutes, you still have to wait 15 minutes for the pressure to diminish, which is the same amount of time it takes to make rice in a regular saucepan.
> 
> Not every Internet recipe writer knows what they're doing.


Well, my "recipe" is terribly simply: grained rice, and just that , and I of course need it for many many kinds of meal, so I still have to look for the best solution for me, even if it consist of buying a new cooker, that's why I asked the brand of cooker all of you use. But I sincerely thank your help and opinion, and the other's,.


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## roadfix

Chief Longwind Of The North said:


> The size of that plug wouldn't create enough pressure difference to cause dramatic change.



Yeah, good point there....   as in an almost completely closed pressure chamber.


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## taxlady

If someone is using a pressure cooker with a gauge instead of weights, I think the possible effects of altitude would be irrelevant. Well, except it might still take longer to get up to pressure.


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## Selkie

Gravity has nothing to do with it. Atmospheric pressure altitude is the determining factor and is more significant than most people realize.
When compared with sea level, a person at 5,000 ft. altitude experiences a pressure loss of 15%. At 10,000 ft. you've lost 30%, so instead of your 11.5 pounds of internal pressure of your pressure cooker, you're only cooking with 8.05 pounds of pressure before the relief valve begins to open.


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## GotGarlic

Josue said:


> Well, my "recipe" is terribly simply: grained rice, and just that , and I of course need it for many many kinds of meal, so I still have to look for the best solution for me, even if it consist of buying a new cooker, that's why I asked the brand of cooker all of you use. But I sincerely thank your help and opinion, and the other's,.



A recipe includes the instructions to make it. The recipe you're using is not working for the conditions you're cooking under. I think medtran's suggestion to ask someone who lives near you for advice is a good one.


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## Selkie

GotGarlic said:


> A recipe includes the instructions to make it. The recipe you're using is not working for the conditions you're cooking under. I think medtran's suggestion to ask someone who lives near you for advice is a good one.



That's the smartest idea yet!


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## Chief Longwind Of The North

This site explains what happens in a pressure cooker quite nicely.  But to understand it you should have a little physics background.  And yes, the weight of the regulator cap determines the inside pressure of the PC.

Seeeeeeya; Chief Longwind of the North


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## Chief Longwind Of The North

Ooops.  I forgot to include the link.  Here it is. https://diracseashore.wordpress.com/2008/09/17/everyday-physics-pressure-cookers/

Seeeeeya; Chief Longwind of the North


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## RPCookin

Selkie said:


> Gravity has nothing to do with it. Atmospheric pressure altitude is the determining factor and is more significant than most people realize.
> When compared with sea level, a person at 5,000 ft. altitude experiences a pressure loss of 15%. At 10,000 ft. you've lost 30%, so instead of your 11.5 pounds of internal pressure of your pressure cooker, you're only cooking with 8.05 pounds of pressure before the relief valve begins to open.



That makes no physical sense.  In the Chief's example, it's weight pure and simple, and that weight is unaffected by changes in atmospheric pressure.  The vent hole is too small and the pressure applied to that point by the controlling weight too great to be affected as you say.  

Your theory would only apply to a valve controlled by a flexible diaphragm where pressure differential could be the determining factor.  This would make using the cooker more difficult because of the differing way that it would cook at different elevations.


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## Selkie

This guy doesn't take into account the change in external atmospheric pressure pressing the escape value weight against the valve hole. His calculations don't compensate for change (sea level vs 10,000 ft.). They only speak to a static setup.
As both a pilot and a submariner, I have just a little experience with changing pressure differentials, not that I claim to be without fault. It has been a while since I had work a problem like this, and my aging brain is admittedly rusty. 
Now it's time for me to go soak my head! Where's my scotch?


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## powerplantop

roadfix said:


> RPC.......But if the ambient pressure is lower then there is less pressure "weighing" that plug down against the relief hole, I would think....



At 12,000 feet it would be 5.35 psi or 36 % less.


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## Chief Longwind Of The North

Selkie said:


> This guy doesn't take into account the change in external atmospheric pressure pressing the escape value weight against the valve hole. His calculations don't compensate for change (sea level vs 10,000 ft.). They only speak to a static setup.
> As both a pilot and a submariner, I have just a little experience with changing pressure differentials, not that I claim to be without fault. It has been a while since I had work a problem like this, and my aging brain is admittedly rusty.
> Now it's time for me to go soak my head! Where's my scotch?



I too worked on submersibles, the U.S. Navy DSRV.  Yes the pressure exerted on the hull of a submersible does affect the inside pressure of the vessel, just as elevation requires aircraft to compensate by pressurizing the cabin.  However, in both cases, the inner pressure is compensated to a degree by the rigidity of the vessel walls.  The inside environment of the Steel spheres of the DSRV resist the intense pressure exerted by the outside water at great depths.  This allows the occupants to stay in an atmospheric environment that will not crush them, or even cause excess gasses to dissolve in their bodily fluids.  This allows them to safely travel to the surface with no ill effects.

This pressure mechanism is independent of the outside pressure forces, within allowable limits, which is determined by the strength of the materials used to make the spheres.

A scuba diver, on the other had, is subject to the full force of the water pressure.  His tank remains at an internal pressure, when full, of 3000 lbs. until he starts breathing.  The airflow to him through the regulator is dependant on the water pressure, which when the ambient pressure increases, it presses on a diaphragm, or valve to open the orifice more, and allow a greater pressure of air to flow to the diver.  This provides sufficient pressure to allow his/her lungs to inflate properly, even though there is more pressure exerted by  the body.

Like the submarine, the PC is a vessel designed to capture and maintain a pressure load, regulated by a weight that requires a certain amount of pressure to lift it and allow steam to escape.  Notice that pressure cookers are not designed to work horizontally, but the valve points upward.  The weight of the regulator presses down over a tiny orifice, trapping the air inside the PC.  When sufficient pressure is achieved to lift the regulator from that orifice, pressure is released.  The regulator weight is literally dancing above the orifice on a column of upward moving steam.  If more weight is applied to the regulator cap, it takes more pressure to lift it.  That's why I said that the main forces that create pressure in the pot are the excitation of liquid, and heating vapor working against the weight, which is a function of gravity and mass.  I thus propose that the temperature inside the PC is independent of atmospheric pressure, as that pressure is exerted from every angle, and does not press the weight against the release orifice.

And yes, I dove as well as working on the DSRV.  Neither activity qualifies me as a pressure expert.  Selkie, if you can produce recognized documents to support your theory, I will step back and state that I was wrong and learned something new.

As to the original question posted by the OP, Check your pressure cooker to verify that all seals, and valves are working correctly.  You may have to turn in your new pressure cooker as defective, and obtain a replacement.  Again, if you know anyone with a pressure cooker in your area, that would be where the best advice would come from.

One more bit of factual info to support my argument.  The weight of air is greater the closer you get to the center of the Earth.   The heavier air has greater density that the air above it.  When a ballon is filled with hot air, the density of the air is less than that of the air around it.  If air pressure pushed downward, the balloon would stay down, as the air around it is heavier.  Instead, the more dense air at the bottom pushes the balloon upward.  This phenomenon is called bouancy.  The air at the bottom of the weight is actually pushing the regulator upward, but with negligible force.  The lesser pressure exerted at higher altitudes still works the same way as the air at the bottom of the weight is more dense than the air above the weight.

Seeeeeeeya; Chief Longwind of the North


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## powerplantop

powerplantop said:


> At 12,000 feet it would be 5.35 psi or 36 % less.



After rereading this I need to clarify The pressure goes to 9.35 PSI or 5.35 PSI less. 

Where this pressure pushing down on the relief will be lower, I think that gravity will be the main thing causing the pressure.


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## RPCookin

powerplantop said:


> After rereading this I need to clarify The pressure goes to 9.35 PSI or 5.35 PSI less.
> 
> Where this pressure pushing down on the relief will be lower, I think that gravity will be the main thing causing the pressure.



While the pressure is in pounds per square inch in the US (atmospheric pressure is 14.7 psi at sea level to 10.5 psi at 10000 feet), the actual surface area that is affected is the area of the relief hole in the lid.  That is a tiny fraction of the one square inch that atmospheric pressure is figured in.  That tiny area on the top of the pressure controller which is affected by any pressure change is insignificant when compared to the gravitational effect pulling down on the heavy controller.  It would result in an effective change of no more than a gram or two, maybe a lot less than that - I don't know how to do the math involved.  Certainly not enough to have any effect on the food being cooked.


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## taxlady

I think the pressure inside the pressure cooker has to be the differential between it and the outside pressure. At sea level air pressure ≈14.7 pounds-force per square inch (psi). Since most pressure cookers can be set to 5 pressure, this would make no sense if it were not the differential. It's has to mean 5 lbs more than the external pressure.


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## powerplantop

RPCookin said:


> While the pressure is in pounds per square inch in the US (atmospheric pressure is 14.7 psi at sea level to 10.5 psi at 10000 feet), the actual surface area that is affected is the area of the relief hole in the lid.  That is a tiny fraction of the one square inch that atmospheric pressure is figured in.  That tiny area on the top of the pressure controller which is affected by any pressure change is insignificant when compared to the gravitational effect pulling down on the heavy controller.  It would result in an effective change of no more than a gram or two, maybe a lot less than that - I don't know how to do the math involved.  Certainly not enough to have any effect on the food being cooked.



The surface area affected by atmospheric pressure would be on the surface of the weight not the hole. But that's still only about a 1 inch area. 

The size of the hole only affects how much internal pressure is applied to the weight to overcome the total forces holding it down. 

All that said when you look at the temp of the water on a steam table 1 or 2 psi change inside the vessel will only give a small change in temp.

But the vessel will start at a lower pressure and the water will boil at a lower temp. But once the weight starts to lift it should be very close to the same pressure / temp as sea level.


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## powerplantop

taxlady said:


> I think the pressure inside the pressure cooker has to be the differential between it and the outside pressure. At sea level air pressure ≈14.7 pounds-force per square inch (psi). Since most pressure cookers can be set to 5 pressure, this would make no sense if it were not the differential. It's has to mean 5 lbs more than the external pressure.



When discussing PSI we normally use PSIG or PSIA. PSI is taken as PSIG.

PSIG means pounds per square inch gage. These gages show 0 with only atmospheric pressure. 

PSIA gages at sea level will show +14.7 with with only atmospheric pressure.


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## taxlady

powerplantop said:


> When discussing PSI we normally use PSIG or PSIA. PSI is taken as PSIG.
> 
> PSIG means pounds per square inch gage. These gages show 0 with only atmospheric pressure.
> 
> PSIA gages at sea level will show +14.7 with with only atmospheric pressure.


So what will the PSIG gauge show at 12,000 ft.? -5.35?

Most pressure cookers use weights, not a gauge.


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## medtran49

High Altitude Cooking and Food Safety 

and, although it's cooked on the stovetop, this site explains the changes needed in pretty simple terms. 

http://www.ehow.com/how_4612282_cook-rice-high-altitude.html


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## CraigC

Chief Longwind Of The North said:


> A scuba diver, on the other had, is subject to the full force of the water pressure.  His tank remains at an internal pressure, when full, of 3000 lbs. until he starts breathing.  The airflow to him through the regulator is dependant on the water pressure, which when the ambient pressure increases, it presses on a diaphragm, or valve to open the orifice more, and allow a greater pressure of air to flow to the diver.  This provides sufficient pressure to allow his/her lungs to inflate properly, even though there is more pressure exerted by  the body.Seeeeeeeya; Chief Longwind of the North



A scuba regulator first stage is adjusted to deliver 120 psi to 140 psi to the second stage. Whether the first stage is a diaphragm or piston design, it depends upon a spring to control the pressure (intermediate) to the second stage. Ports in the first stage, open to the ambient environment, allow the first stage to deliver intermediate pressure to the second stage above the ambient pressure. The second stage has a diaphragm that depresses a lever when the diver draws breath. It is also exposed to the ambient pressure. The second stage is "tuned" to the intermediate pressure via a spring and seal which will only allow flow when the lever is depressed either by the diver drawing breath or manually depressing the purge button. Whether the diver is drawing breath at the surface or at depth, the regulator performance will remain the same.

Sorry Chief, your description of operation was not quite accurate.


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## Addie

RPCookin said:


> The only pressure cooker I've ever seen in action was my mother's.  It was an old Presto (had to be pre 1950), and the relief valve was nothing more than a hole in a stem in the center of the lid, and you  used a weighted plug sort of thing that just rested on top of the stem.  It was the weight of that plug which regulated the pressure, and when the cooking was over, you just took that off and it depressurized through the relief hole in a few seconds.
> 
> That one would have cooked to the same internal pressure no matter the ambient atmospheric pressure because it was controlled by gravity.



Your mother and I  had the same PC. It made the greatest Yankee Pot Roast for Sunday dinner. You never had to worry about getting the meal on the table on time. You knew you could turn to your trusty Presto PC. 

The regulator was removed when the food was cooked. It got washed under running hot water, dried and placed right back in the top drawer where it belonged. Nobody dared to remove it. Along with the scissors in that drawer. Small items had a specified place and it never changed. Including my Presto regulator.


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## taxlady

medtran49 said:


> High Altitude Cooking and Food Safety
> 
> and, although it's cooked on the stovetop, this site explains the changes needed in pretty simple terms.
> 
> How to Cook Rice at High Altitude (3 Steps) | eHow


Well, that first link pretty much resolves the question. Yes, you do need higher pressure in the pressure canner at higher altitude.

Thank you Medtran.


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## RPCookin

powerplantop said:


> The surface area affected by atmospheric pressure would be on the surface of the weight not the hole. But that's still only about a 1 inch area.
> 
> The size of the hole only affects how much internal pressure is applied to the weight to overcome the total forces holding it down.
> 
> All that said when you look at the temp of the water on a steam table 1 or 2 psi change inside the vessel will only give a small change in temp.
> 
> But the vessel will start at a lower pressure and the water will boil at a lower temp. But once the weight starts to lift it should be very close to the same pressure / temp as sea level.



Think about what you are saying.  Sure there is 14.7 psi on the top (at sea level), but there is also 14.7 psi pushing on the bottom and sides, everywhere except for the tiny spot where the weight rests in the hole.  

Before you apply the heat, there is equal pressure on every surface of the weight including the point on the hole.  Pressure is balanced over the entire surface, no matter what the elevation.  As heat builds inside the pot, so does the pressure on the point of the weight that rests in the hole, pushing back against gravity and atmosphere.  The ambient pressure doesn't change anywhere else, so the only point where an imbalance in pressure can have an effect is the tiny surface area that is directly opposite the point affected by the internal pressure.  Since that infinitesimal difference is mostly negated by the weight, it becomes irrelevant in any practical sense.

Water starts to boil at a lower temperature, but as the pressure builds that boiling point has to rise too, mostly negating the higher elevation.  I may be all messed up, but this is how my logic sees it.  Since I don't own a PC, it is really just a discussion for me.


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## powerplantop

taxlady said:


> So what will the PSIG gauge show at 12,000 ft.? -5.35?
> 
> Most pressure cookers use weights, not a gauge.



Most gages showing PSIG are vented to atmospheric presure. For those at 12,000 ft alttitude they will still show 0. 

The one in the OP loks to be a weight and not a valve.


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## jennyema

Are you following the instruction manual that came with the pressure cooker?


I've never heard of taking it off the heat completely when it comes to temp.


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## Chief Longwind Of The North

I am unclear of the OP's cooking method.  The correct method for using a pressure cooker is to place the food into the cooker, add the appropriate amount of liquid, secure the lid and regulator and turn on the heat source.  When the regulator starts lifting, as is shown by the escape of steam, and movement of the regulator, you set the timer for the recommended period of time.  When that time has elapsed, the quickest way to reduce the internal pressure is to place the PC into the sink and run cold water over it.  There is usually an indicator valve that will open when the PC is safe to open.  If not, simply remove the regulator while running water over the PC.  When steam no longer emerges from the valve, pressure is equalized inside and out, and the PC lid can be safely removed.

The key to PC timing is to start timing when the pot comes up to the proper internal pressure, then reduce the heat until the regulator just barely moves.  Cook for the recommended time.

Seeeeeeeya; Chief Longwind of the North


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## Chief Longwind Of The North

Selkie, this discussion has me taking in one more bit of info than I had initially considered.  I still believe that the weight of the regulator is the primary force that controls the internal pressure.  However, Before the cover is placed on the pot, the air at the higher elevation is thinner, with less particulate mass per square inch.  It exerts less pressure at any given temperature than air at lower elevations as there are not as many molecules striking the inner surfaces of the pot.  When the lid is first secured to the pot, the liquid would indeed boil at a lower temperature, thus the ineternal temperature of the pot would be lower.  Because of the more rarefied atmosphere, it would take longer for the water vapor to create sufficient pressure to raise the regulator weight.  Once reached however, the internal temperature would be the same as at lower elevations.  It would also require the application of more eternal energy to maintain that internal pressure for the same reason.

I suspect that at any elevation, over time, as vapor escapes through the steam valve, the temperature would cool if a constant external energy was applied to the pot because again, less molecules means less internal pressure, to a point.  So yes, your were correct, but not because any pressure was exerted on the regulator by ambient atmospheric pressure, but because the internal pressure was lower to start with.

Still, without experimentation, I couldn't say how much longer the pot would take to come to temperature at varying elevations.

Seeeeeeeya; Chief Longwind of the North


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## Selkie

I see your point. At the risk of sounding pedantic, I'm going to withdraw from this discussion before we begin calculating how many moles of nitrogen and oxygen there are at a given temperature and pressure in determining the value of water vs chicken soup! I feel like Larry, Moe and Curly.


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## Chief Longwind Of The North

Selkie said:


> I see your point. At the risk of sounding pedantic, I'm going to withdraw from this discussion before we begin calculating how many moles of nitrogen and oxygen there are at a given temperature and pressure in determining the value of water vs chicken soup! I feel like Larry, Moe and Curly.



I'm not feeling quite like Larry, Moe, and Curly.  But I am feeling much like a sophist, talking about things just for the sake of discussion, and not really accomplishing anything useful.  I too am stepping away.  Still, it was an interesting discussion.

Seeeeeeya; Chief Longwind of the North


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## Josue

Hi, I wanted to tell you what I finally did.
As my PC has a relief valve which closes the hole using its own weight, I put one coin on it and after waiting for 10 minutes and lifting the relief valve (for me to be able to open the PC sooner), the rice was very well cooked. I guess with 8 minutes would have been enough.
I am happy that somehow we managed to reduce the total time needed.
Before I used to wait for 15 minutes + another 15 before opening the PC, but now what I did was to wait for 10 minutes + 2 minutes (lifting the relief valve), and I could open the PC inmediately.
At first I put four coins, but the result was dramatic, at some point I lifted the four coins and A LOT of foam and steam started coming out very fluently, I felt my PC could exploit , I got a bit scared and put the fire out, after that I left just one coin.
By the way, the people near me who have PC don't use it to cook rice, that's why I couldn't get much information from them. I do live in Oruro, where we are at 3735 meters above the sea level and gravity is 9.76 [m/s^2] instead of 9.81 [m/s^2] at sea level.
I will continue trying to understand the physical reasons behind all the behaviour of this things. I very very much thank your help and opinions. Cheers.


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## taxlady

Josue, I'm glad to read that you figured out a solution.


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## jennyema

Josue said:


> Honestly I didn't try it, I bought the cooker to make grained rice. I can try to cook fried chicken meat, how much should I have to wait for it to be cooked?


 

Its very dangerous to use oil in a pressure cooker unless it was specifically designed as a "pressure fryer."

So unless yours is, I wouldn't think of doing it.

Particularly since yours apparently has no instructions ....


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## medtran49

Josue, 

You can probably get instructions from the Internet.  Just Google the make and model, which should be imprinted on the bottom.  That's how I got the instructions from the one we inherited.


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## roadfix

Good to hear that the additional weight of the coin over the relief hole made a noticeable difference.


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