Thermal cooking with the Tiger “magic pot”

Empty inner potA couple weeks ago, I finally bought a thermal cooking pot. It’s been on my radar for a long time, and I finally splurged. The basic idea is that it’s a pot-in-a-Thermos. You put your ingredients in the inner pot and bring it to a boil on the stove, then put that pot into the insulated outer pot, close the lid, and the food cooks using the retained heat. It’s sort of like a countertop version of haybox cooking, and the idea is to save energy and keep from heating up your kitchen when cooking.

I’ve learned that this gizmo has definite strong and weak points. I’m honestly not sure I’d recommend buying one; they are pretty pricey and it doesn’t do everything I’d hoped it would. Still, it works really well for some things, and I can’t stop experimenting! I thought I’d post the results of my experiments to date, so if you’re considering getting one, you can make a really informed decision. Details after the cut:

Excellent Results

  • Empty outer thermal pot

    Beef stew. I browned a slice of beef shank and some meaty bones in the pot with a little oil and onion, then added water up to about 2″ below the top of the pot. (This is considerd “full.”) After it had boiled for 15 minutes, I put it into the outer pot and let it sit for 2 hours. Then I brought it back to a boil (which took only a minute or two) and put it back in the cooker for another hour. At that, point I had a really nice pot of beef stock. It was still steaming hot when I put it in the fridge overnight. The next day, pulled the meat off the bones and added carrots, onions, kale, barley, salt, and seasonings. Brought it to a boil and dropped it into the cooker for 30 minutes, and it was probably the best beef barley soup I’ve ever made. The carrots retained a nice “bite” and the barley was fully cooked. Usually, the carrots are overdone by the time the barley is cooked.

  • Yogurt. This was the exception to the rolling-boil rule. Heated the milk to 180, cooled to 110, added diluted starter, and popped it in the pot overnight. In the morning, it was yogurt, with no attention, energy, or re-warming needed. I definitely prefer this over our previous cooler-with-hot-pack method.
  • Coconut vegetable curry. Can of coconut milk, can of tomatoes, and a lot of chopped vegetables (including white and sweet potatoes). Bring to a boil, pop in pot for 30 minutes. Quite tasty; all veggies done nicely.
  • Taking hot food to a potluck. It’ll keep food hot for several hours without added heat or electricity, so this is perfect for taking a pot of curry or chili to a potluck.
  • UPDATE 10-31-09: Beans. I filled the pot a little over halfway with water and threw in a cup and a half of dried black-eyed peas. Soak overnight, bring to a boil, and throw in thermal sleeve for…a while. I had to go out, so mine were in there around 4 hours, and they were *perfect* when I got home. Cooked through, but not at all mushy. As an added bonus, black eyed peas do not make my heart race the way other beans do!
  • UPDATE 11-3-09: Potatoes. Dice and cover with cold water (pot half full); bring to a boil and let sit in thermal sleeve for about 20-30 minutes.
  • UPDATE 1-15-10: Making cheese. Bring up to temp over med-lo heat on stove, then pop into sleeve. Keeps it at a steady temp for at least 2 hours without having to fiddle with it or worry about burning.

Middling Results

  • Chicken stock. Eventually, I did get good stock and tender chicken out of the pot, but it took several re-warmings and 4-5 hours of “steeping” time. I was also making stock out of the same batch of chickens on the stove, and to be fair, it took about 4 hours on a constant simmer. These were some tough old hens, and while the stock was great, the chicken never really got meltingly tender (even after pressure canning). I will continue to make stock in this pot when I’m doing one chicken at a time.

Poor Results

  • Place inner pot and lid into outer potSplit pea soup. The batch was so small (1c peas and 3c water) that not enough heat was retained to cook them.
  • Brown rice. I’ve tried this four times and ruined a really depressing amount of rice, both because of my own failure to measure ingredients, and the pot’s failure to cook.
    • 2c rice, unknown water = fairly crunchy rice. Hmm, did I put in 2 or 4 cups of water? Well, I’ll just add some more hot water, like I do on the stove and I’ll end up with…wallpaper paste!
    • 2c rice, 3c water = slightly crunchy rice. Um, Em? Do you remember that rice is supposed to be made with TWO cups of water for every cup of rice? No? Well, don’t you think it would be a good idea to MEASURE YOUR INGREDIENTS PROPERLY before blaming equipment failure? That’s a good girl.
    • 2c rice, 4c water = fully cooked rice floating in a lot of hot water. You see, this pot doesn’t let steam out the way a pot on the stove does, which is why the 2c water/3c rice was only slightly crunchy. I just dumped this batch into a sieve and let it drain, and it actually was the best batch to date. Not perfect rice, but it was edible. Next time, I will try cooking 2c rice in 6 or 8c water and just plan to drain it like pasta.
    • 1c rice, 2c water with complicated “double boiler” arrangement inside the pot = total failure. My idea was to put the rice and water inside a stainless steel bowl, and surround that with boiling water. I think the idea bears repeating, but by a different method – perhaps using a Mason jar on a silicone hot pad (so the jar doesn’t crack) with a lot more water around it so the inner pot can actually boil.
    • 2 c rice, enough water to fill pot half full. Let it stand for one hour and it was completely overcooked.

Lessons Learned

  • You must bring the contents of the inner pot to a full, rolling boil for a couple minutes before putting it into the thermal outer pot.
  • The pot works best when it’s full (80% of 4.5 liters, in this case).
  • It works poorly or not at all when it’s not full.

At one point, Thermos made a 6L version of this that came with two pots. You could either cook 2 different things at the same time, or fill one with water to help the other one cook. I can’t find it now, and I’m not sure if the difference between 3L and 4.5L would be enough to, say, get my rice to cook.

Next Steps

  • See if I can find a way to do a pot-in-a-pot method that will let me cook smaller quantities of food.
    • UPDATE: This hasn’t worked terribly well, though I did get a passable split pea soup by putting the soup ingredients in a small stainless steel pot and filling the thermal pot *around* it with water.
  • Compare to a standard pressure cooker, which also uses less fuel than regular stove-top cooking, but does so at much higher heats. Supposedly it’s faster, too, but I’m not sure that it will be once you take cool-down/depressurizing time into account. But it might do a better job with rice and other things made in 1L instead of 4L quantities.
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9 Comments

  1. Tammy Coxen said,

    October 17, 2009 at 7:42 pm

    I have a pressure cooker you could borrow if you’d like. I don’t use it as much as I should, but it cost me $1 at a yard sale, so I get my money’s worth must making my 11-minute cranberry sauce recipe once or twice a year. It’s certainly going to be much more time efficient than your thermal pot for things like soups and stocks.

  2. MK said,

    October 18, 2009 at 6:32 am

    I do love my pressure cookers – but their advantage to me is to make something that would take a long time in a short amount of time. Like soups or stock. I have a skillet sized one that I use to make pork chops and things like that in.

    I guess something similar could be done as your pot by placing a pot inside a bigger pot with some insulating material around it. Although the better bet might be to choose something with better insulating capabilities for the outer vessel like or a pot inside a box full of dishtowels or something. Is that what “haystack cooking” is all about? I’ll have to read up on that. Have you tried the dutch oven cookery where you dig a hole in the ground and put the oven with some coals in the hole? I’ve been thinking about trying that – the only thing that’s stopping me is my yard has way too much clay to make the digging of the hole easy.

  3. El said,

    October 30, 2009 at 2:42 pm

    Wow, this is the first time I am hearing about these pots and I find it very interesting. Hmm (she says, sizing up the uses).

    One of the things we’re looking into if and when we ever redo our kitchen is an invection cooktop. Tons less energy used. You need ferrous pans, though there is a converter “puck” that you can buy (which is good because I have one beloved copper braiser). They’re coming down in price a lot; they’re half what they were 3 years ago. But: I will save my old electric monster stove and put it downstairs for canning season only.

    I love how you’ve charted your highs and lows.

  4. Hong said,

    October 31, 2011 at 4:04 am

    I am interested in this pot, where can I buy it?

    • Emily said,

      October 31, 2011 at 7:37 am

      Amazon.com has them. You can also find them at large Asian grocery stores (the one on Washtenaw in Ypsilanti has them, if you live in my area).

  5. Valerie Daniels said,

    December 2, 2012 at 7:28 pm

    I’ve had one for about 10 years now, and love it for quantities of food, especially around thanksgiving or potlucks. I can keep mashed potatoes hot in it and is great if you like to do a lot of soups. You do have to keep it almost full and bring it boil so all the ingredients are hot enough to stay hot as the author said. Some of the failures listed I would attribute to user error. I much prefer it over a slow cooker which tends to lend an overcooked taste to foods. That never happens with this pot. I also love the fact that it doesn’t make the kitchen hot in warm months.

  6. Nick said,

    February 13, 2016 at 12:39 pm

    Have you tried leaving the food in there longer? I tend to do much longer cooking times. 8-10 hours for soups and 24 for stock with one reboiling about 12 hours in. I was impatient and did 3 hours recently and it was not enough. I’ve gotten good results with lonf times for any kind of stew meal or soup. 24 hour chicken stock is fantastic. I agree on rice, I haven’t figured that out. I need to try beans in my 1.5 liter one.

    I have the Thermos shuttle chef 4.5 liter and it’s always a good bit above 140 degrees after 12 hours so I feel comfortable cooking that long. For the stock I just bring it to a boil again at 12 hours in. The 1.5 liter version isn’t quite as good at retaining heat but it still works great.

  7. Arcie said,

    June 7, 2016 at 1:44 am

    Hi there, I too like to use the thermo cooker and love to cook! I like to offer a suggestion for cooking brown rice. Soak the brown rice for at least 2 hours. Reduce the water by ⅛ of a cup per one cup of rice. Also, add one teaspoon of vegetable oil to the water. Bring the pot to a rolling boil for at least two minutes. Transfer to the outer pot with out uncovering the inner pot. Open after at least 45 minutes and the rice will be nice and fluffy! I hope this helps!


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