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Bob S
03-09-2008, 16:35
I have been looking at the GSI Pressure cooker all winter; I was wondering if anyone has it and wanted to know how it works. The advertising says that it saves 2/3 cooking time. For the times when I don’t use a wood stove a 2/3 saving in cooking time could add up to a big fuel savings.

I have several other GSI items and have been very happy with them, they are well made. I have no reason to think it’s advertising hype, but it’s hard to imagine 2/3 less fuel usage.

I did a search with Google and got no meaningful reviews.

Tinker
03-09-2008, 16:55
My mother used to pressure cook chicken all the time when I was a kid. The pressure inside the cooker makes things cook faster. It made the chicken melt-in-your-mouth, fall-off-the-bone tender, too. For cooking dehydrated foods it might be just the thing, but for the weight cost, you might be better bringing a pot or cooking bag cozy. I couldn't see myself using a pressure cooker for Ramen or Knorr type dinners.

generoll
03-09-2008, 17:23
A pressure cooker works by increasing the pressure (duh) and therefore the caloric content at which water boils. Which is to say that it will take more heat to get the water to boil off and therefore cooks in less time. It might cook in 2/3 the time, but I'm not sure about using 2/3 the fuel. Probably some fuel savings, but it will take someone like Dances to actually calculate the fuel savings.

GGS2
03-09-2008, 20:05
Best use would be for things like brown lentils, beans, brown rice, meat and some of the harder to cook vegetables. Most things cook just fine in an open pot. On canoe trips I used to use a wide mouth thermos for extended cooking times, like the cosy method. If I were canoeing I would definitely consider a pressure cooker. Not so much backpacking unless you plan on cooking any of the above a lot.

take-a-knee
03-10-2008, 00:36
A pressure cooker works by increasing the pressure (duh) and therefore the caloric content at which water boils. Which is to say that it will take more heat to get the water to boil off and therefore cooks in less time. It might cook in 2/3 the time, but I'm not sure about using 2/3 the fuel. Probably some fuel savings, but it will take someone like Dances to actually calculate the fuel savings.

I've read that climbers use them for high altitude base camps, maybe more to counter the low boil times at high altitude, I don't know. I'm sure the fast/light/alpine types don't hump them.

fiddlehead
03-10-2008, 03:34
Yes, the Sherpas in Nepal use them all the time. I've camped with them a few times at high altitude (for me anyway, 15k and 17k feet) and they used them. I think they mostly were cooking lentils though. and maybe rice (long grain of course)
Keep in mind that the pressure would build quicker at those high altitudes than for you at near sea level.

I often thought it would be a good idea to try some things on one if someone came up with a lightweight model. If you get it and experiment, please post back here and let us know your results.

It still takes time to get them up to pressure and for economical (fuel saving) backpack cooking, if you put your food in when you start and the water's still cold, it'll be half cooked by the time your water boils anyway. Also, just bringing things to a boil and then turning off the stove and covering (all the time), well you can cook and eat this way although it may not taste as good but you'll be hungrier anyway so it'll be ok. (i get almost a week out of a small butane/propane canister using this method)
But to pack lentils, beans, long-rice, etc. and be able to cook them fast without much added weight could be a plus.

NICKTHEGREEK
03-10-2008, 05:53
Great way to cook a whole cauliflower fast--at home.

Dances with Mice
03-10-2008, 08:59
Probably some fuel savings, but it will take someone like Dances to actually calculate the fuel savings.That's such a nice way to say "a nerd", Gene.

I've only used pressure cookers for home canning where the idea was to get the temperature to a certain level then hold at that temp for a period of time, energy saving wasn't important. It seemed to suck up a lot of energy but I was using a relatively large cooker that held four 1-quart jars. But you have to heat the water & food to boiling, obviously, then past that awhile until the pressure builds. It took some time for the system to pressurize, but like I said it was a big canner. During canning I would keep the heat cranked up until the batch had processed, for cooking I suppose you could turn off the heat and let it coast for awhile, cooking while the cooker cooled and save fuel that way. I'm sure there's some tricks like that to be learned from experience. There always are.

I haven't used them for direct cooking, although I hear it's possible to really speed up slow cooking items like pot roasts. One major problem with them is that you can't see the food while it's cooking. Every other cooking method allows a visual check or a taste test, then you can modifiy your technique while cooking (like keep cooking longer, add spices, add water, let it cool, whatever). The pressure cooker, once opened, would be a hassle to re-assemble for more cooking so I suppose one would want to err on the long side of cooking times.

And that's all I have to say about that.

Heater
03-10-2008, 09:05
And that's all I have to say about that.

Well, I thought it was a very nice story. ...and you tell it so well!

Frosty
03-10-2008, 10:19
A pressure cooker works by increasing the pressure (duh) and therefore the caloric content at which water boils. Which is to say that it will take more heat to get the water to boil off and therefore cooks in less time. It might cook in 2/3 the time, but I'm not sure about using 2/3 the fuel. Probably some fuel savings, but it will take someone like Dances to actually calculate the fuel savings.It should use a lot less than 2/3 the fuel, actually.

Less, you need to put more heat into the water to boil it, but several factors are at work:

1) it is a more or less closed system. No heat escaping via the lid.

2) items cook quicker because pressure actually forces super-heated steam into the food

3) a pressure cooker doesn't really work by heating the caloric content of the water. A pressure cooker is more of a steam cooker. You use very little water. So even though you put a little more heat into the water to raise the temp for 212* to around 240*, you are doing to to 1/10th of the amount of water.

The thing that is wrong with pressure cookers on the trail is weight. Cookers typically double atmospheric pressure (the add 15 psi). Doesn't sound like much, but you don't want to be standing around a pot of 240* water and steam if the pot ruptures.

So the pot must be heavy. So heavy that it will weigh a LOT more than the weight of the fuel which you will save.

Alligator
03-10-2008, 10:29
The GSI model (https://www.campmor.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&krypto=J4RGVCOx1NUYX9rrhIiCX5sUgkzX4NvDb2t%2Fmi%2B ALE8nrGMv1ho8OVMOIbX9bvY4jshWHBqBNt7J%0AIyF3qRbyqP Mu%2BcrVlWFhoSYYQgQ6eq2hbASuJbtAEOG16gtZXn%2Bn)at campmor weighs 3lbs 6oz.

zelph
03-10-2008, 10:51
Pressure cooking with an alcohol stove works well. Just need to practice a little.

http://www.whiteblaze.net/forum/showthread.php?t=22425&highlight=pressure+cooker&page=8

generoll
03-10-2008, 11:37
I suppose it's kind of a moot point since no one is likely to carry a pressure cooker in their pack, but when I use mine at home I have to turn the heat higher to keep the pressure cooker pressurized. An unscientific measurement to be sure, but nevertheless a valid observation. Since steam contains approximately 273 times as many calories as water it does take a bit more heat to load up a pressure cooker. It's probably also a more efficient use of the heat, but whether the savings in time equals the savings in fuel remains unproven in my mind.

budforester
03-10-2008, 12:03
Waaay back when I was young, I wished for a pressure cooker. I could have carried the extra weight, but didn't have the cash. At 12,ooo feet I could have made brown rice and lentils... probably take 4 days without a pressure cooker. Now I precook- dehydrate- rehydrate, and don't need a pressure cooker.

Allen66
03-10-2008, 12:06
The whole consept of a pressure cooker involves the fact that water boils at 212 degrees at sea level. As the water boils it raises the pressure inside the cooker. For each pound per square inch in pressure gained it raises the boiling point of water by about 3 degrees. if you bring the pressure up 15 psi you are raising the cooking temp about 45 degrees. 212 + 45 =257 degrees of cooking temp. this is why a pressure cooker cooks faster. Laws of thermodynamics.

generoll
03-10-2008, 12:08
I reread the initial post and see that GSI doesn't claim 2/3 savings in fuel, but rather 2/3 savings in time. That seems like an honest claim. It appears that the poster imputed the fuel savings.

generoll
03-10-2008, 12:15
Ah, gotta love thread creep. Anyway, let me keep the pot boiling, to use a bad pun.

An unpressurized pot will lose heat as the water boils off. Turn up the heat and you don't cook faster, you merely boil off the water faster. Water increases in temp by 1 deg C for each calorie added. Water at the boiling point takes 273 calories to turn from water to steam. By using a pressure cooker you are keeping that heat in the pot rather then letting it escape as steam.

There, have I left any nit unpicked?

Oops, I should have mentioned that I am speaking of one gram of water when I mentioned the change in temp or physical state, but I'm sure you all remember that from your high school chemistry anyway.

Allen66
03-10-2008, 12:27
Ah, gotta love thread creep. Anyway, let me keep the pot boiling, to use a bad pun.

An unpressurized pot will lose heat as the water boils off. Turn up the heat and you don't cook faster, you merely boil off the water faster. Water increases in temp by 1 deg C for each calorie added. Water at the boiling point takes 273 calories to turn from water to steam. By using a pressure cooker you are keeping that heat in the pot rather then letting it escape as steam.

There, have I left any nit unpicked?

Oops, I should have mentioned that I am speaking of one gram of water when I mentioned the change in temp or physical state, but I'm sure you all remember that from your high school chemistry anyway.


By using a pressure cooker you are adding pressure to the equation (hence the name pressure cooker), pressure increases the amount of heat required to boil water, therefore cooking at a higher temp. At 15psi water boils at approximately 257 degrees

generoll
03-10-2008, 12:46
Oops redux:

It's been a couple of years since high school. A quick Google tells me that I was off on the Laten Heat of Vaporization. Way off. The correct number is 540 cal/g. Now we can all rest easier.

envirodiver
03-10-2008, 12:52
And that's all I have to say about that.

Life is like a box of chocolates isn't it DWM.

Frosty
03-10-2008, 16:12
I'm sure you all remember that from your high school chemistry anyway.I remember 6.02 x 10 ** 23. Something about cooking moles and avocados in a pressure cooker :D

Allen66
03-10-2008, 16:29
I remember 6.02 x 10 ** 23. Something about cooking moles and avocados in a pressure cooker :D

sounds like the makins for a stew:banana:D:banana:D

atraildreamer
03-12-2008, 16:59
In the downloadable spreadsheet in my Stove Efficiency thread:

http://www.whiteblaze.net/forum/showthread.php?t=19616

there is a chart (adapted from data supplied by Jason Klass,
and also available at his website:

http://www.freewebs.com/jasonklass/

that shows the variation in boiling points at various altitudes.

On top of Everest, water boils at 158 F (70 C). There is even a noticeable drop on the top of Clingman's Dome (the highest point of the AT) to 199 F (93 C).

While a 13 F (7 C) drop probably would not be a problem on the AT, the 54 F (30 C ) drop on Everest is certainly significant and would necessitate the use of pressure cooking to properly prepare food.

I have considered the idea of pressure cooking meats before drying to make jerky as a way of extending the shelf life of the prepared jerky. Most dehydrator sites recommend the baking of the final product at at least 160 F for one hour to kill any remaining nasties. My thought is that the higher pressure and temperature would accomplish this in the same manner that a sterilyzing autoclave is used to sterilyze labware. Additionally, the addition of the spices, etc., to the pressure cooker, may give a more consistent flavor to the finished product.

Has anyone tried this? If so, with what results? :confused: