Gunner Quinn
This article refers to what happens if you break all the rules while using a pressure cooker. It refers only to stove-top models, not electric models such as Instant Pot which I have no experience with.
My First Pressure Cooker
Many people don’t own a pressure cooker because… Who wants a bomb in the kitchen? I worried about the same thing the first time I ever used one. I warned my family ahead of time that I was taking the new pressure cooker on a trial run. I instructed them to be on alert and if they heard me yell, “She’s gonna blow!” they were to grab the cat, run for their lives, and get out of the house as quickly as possible. As a primer we watched the scene from The Sandlot where the boys are all diving out the windows of the tree fort moments before the vacuum cleaners explode. When we were all ready and had our tightly-laced PF Flyers on, I fired up the pressure cooker. I cooked some dry beans for chili and it was very uneventful. My kids were disappointed they wouldn’t have a good story to tell at school the next morning.
Summary
I’ll cut right to the chase: I wasn’t able to get my pressure cooker to “explode” in the normal sense of the word. I did however, discover other things which help me rest easier now when using my cooker and what features to recommend when friends and relatives are buying one.
First and foremost, pressure-cooker problems are not that common to begin with. We only hear about the one-in-a-hundred-thousand that happen, not 99,999 that don’t. When problems do arise, it’s almost always due to the small steam-escape tube clogging with food. This can only occur due to human error, generally from overfilling the pressure cooker. If the pressure cooker is being attended to, the user can immediately tell the moment a clog occurs: the gently rocking cap quits moving. Turning off the heat at that point removes any possibility of danger.
Clogging is easily prevented by 1.) visually checking the steam vent before using the cooker, then 2.) following the user manual or recipe instructions on how full to fill the pressure cooker for each type of food.
In a smaller percentage of cases, dangers can occur when a damaged or worn-out lid gasket is used. Gasket issues are generally not dangerous since they prevent the pressure cooker from pressurizing in the first place.
Finally, pressure cooker explosions are almost unheard of with today’s safety features built into every home pressure cooker. A rapid steam release can happen if the pressure cooker has a safety plug instead of a safety valve, but this plug can only blow out if the user fails to turn off the heat if the cap quits rocking.
Bottom line: pressure cooker problems are uncommon and only occur due to human error. This article shows you how to avoid those altogether so you can use your pressure cooker worry-free.
In the last section (in Part 2) I’ll walk the reader through the idiot-proof method I use to cook a batch of dry beans for chili to show how easy and safe using a pressure cooker is.
Terminology – I’m uncomfortable with the term “explosion” to describe pressure-cooker events. When pressure cookers first became popular in the 1950’s they lacked today’s modern safety features. They could literally explode, meaning they blew their lids and sometimes even threw shrapnel, much like a bomb. With today’s safety features, a pressure cooker can’t explode that way. Therefore, in this article I’m referring to “explosions” as a rapid steam release. While it can be dangerous, a steam release typically only startles the user and can sometimes make a mess in the kitchen. In more serious circumstances for those standing nearby, a rapid steam release can cause 1st and 2nd-degree burns. Both of these situations are uncommon and easily avoidable if the simple rules are followed.
How Pressure Cookers Apply to a Grid-Down Lifestyle
Artificial stove fuels such as propane will need to be severely rationed in a TEOTWAWKI world. For me, propane’s only use will be for cooking, not for energy-hog uses such as heating water, and certainly not for home heating.
In order to stretch our propane as far as possible, a pressure cooker will be an important fuel-saving piece of cookware. As an example, pressure cookers can reduce the time for cooking a batch of beans from an hour once it begins to boil to three minutes.
How Pressure Cookers Work
Let me begin by saying the reason why modern-day pressure cookers can’t literally explode is due to several built-in safety features that prevent it. All have a lid which locks in place one way or another. Some of the older and less-costly pressure cookers have a simple rubber blowout plug. When the steam vent clogs, the plug blows out and lets off a potentially dangerous blast of steam. The safest pressure cookers have a spring-loaded safety valve which produces a small controlled steam release. In addition to a spring-loaded safety valve, the best cookers have a second safety feature: a button which pops up and, like a whistling tea kettle, audibly alerts the user to turn off the heat.
By design, pressure cookers maintain the proper safe pressure when a small weighted cap, some resembling those on a common cooking-pot cover, rocks back and forth over a small tube which passes through the lid. With each rock, a small amount of steam is released. When the cooker is at full pressure, the temperature inside the pot rises from the normal 212° F boiling-point of water to the faster-cooking temperature of 250° F. The weighted cap is sometimes referred to as the pressure regulator, jiggle valve, weight, or the weighted cap. In this article I’ll simply refer to it as the cap.
This article will show you how to easily prevent your pressure cooker from becoming dangerous by letting these safety devices do their jobs. As long as your read the user manual, follow the few basic rules, and keep an eye on the cap to be sure it’s rocking back and forth, you can’t have any problems. I’ll walk the reader through a bean-cooking example which has a near-zero chance of having any issues for the user.
What Happens If the Rules Are Broken?
I designed and performed some experiments, not so I could have fun blowing stuff up (okay, that was part of it), but so I could better understand how severe the results can be when breaking the pressure-cooker rules. Knowing the specifics and the probabilities of them happening in the first place would help me be less nervous when using my pressure cookers.
In that high-school physics class way back when, I learned the Ideal Gas Law: pV = nRT. There’s no quiz at the end of the article so you don’t need to memorize that, it’s just a fancy way of saying that as a substance like water heats up inside a closed container, the pressure will increase and in the process so will the boiling point of the water. The reverse is also true. When canning, a head space is left in the top of each jar. After the jars are removed from the canner, the air in that head space will cool, take up less space, and form a suction. This suction pulls the button down on the jar lid assuring us there’s a good seal.
Understanding how the ideal gas law applies to pressure cooking, I knew why the things I was testing would happen, I wanted to know exactly how those things would be expressed.
The Experiments
I had an older aluminum pressure cooker that would be perfect for my experiments so I wouldn’t risk possibly damaging either of my two full-time stainless-steel pressure cookers.
Before starting, I checked the lid gasket to be sure it was still pliable with no holes, cracks, or tears. Next, I checked the steam-escape tube in the lid to be sure it was clear and not blocked by old food particles or dried clay from my local mud-dauber wasps. I then checked the cap to be sure there were no issues with the tip which comes in contact with the vent tube.
Not wanting a potential mess in my kitchen, I took the pressure cooker and my butane backpacking stove outside. I added a quart of water to the cooker, then to make the experiments more realistic I added a pint of cooked chili.
I needed a way to remove the steam-vent cap from a safe distance to prevent any chance of injury from steam or chili. I jury-rigged a tripod using t-posts, then attached a fence clip to provide a smooth loop for bailing twine to slide through. I tied bailing twine to the cap, then lowered the cap onto the lid. I reeled out 10’ of bailing twine, lit the stove, and stepped back.
With everything set up and ready to go, there were four things I was hoping to find answers for:
Constant high heat – When the cooker reaches full pressure, the cap moves quite a bit with a lot of steam escaping. Normally, I reduce the heat at that point mostly to save propane but also because I wasn’t comfortable with the cap jumping around so much. The first thing I wanted to know was whether constant high heat during the cooking process could cause any problems. Could too much steam over an extended period rock the cap violently enough to blow it completely off?
In this first experiment, after the cap started rocking I waited five or six minutes with the burner on high heat. There was more steam than usual coming out with each rock of the cap and it was dancing around with much gusto, but aside from that nothing happened.
Sudden removal of the cap – The second thing I wanted to test was what happens when the cap is suddenly removed during cooking. The formula pV = nRT says when the cap is removed, the pressure drops so quickly inside the pot that much of the hot water inside turns to steam almost immediately. I expected a steam-and-chili geyser to form when the cap was suddenly removed.
While the cap was still rocking on the pot under the tripod, I pulled on the bailing twine to raise the cap but it was catching on something and wouldn’t come off easily. Twice as I pulled on the twine to jiggle the cap, large amounts of steam escaped with each jiggle. The third time the cap finally came off with a geyser of steam rising into the air. Instead of slowly diminishing as the pressure decreased, the geyser stopped abruptly as if a valve had been turned off.
(To be continued tomorrow, in Part 2.)
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