Trekmates – Flameless cooking flask

The single most important thing on any camping trip – more important than a good tent, a warm sleeping bag or decent weather – is a cup of steaming hot tea in the morning. Indeed, on any given Sunday morning across the country’s campsites, if you listen carefully you can actually hear faint mews of hungover, damp and smelly campers crying ‘tea… please… anyone’. So any new invention which provides a safe way of making a cup of the good stuff without having to leave the warmth of your sleeping bag deserves a bit of fanfare.

The prototype flask steams away merrily in a field near Leamington Spa

Trekmates have the exclusive UK licence for a system which uses a chemical reaction between a sachet of ‘secret ninja stuff*’ and water to create an intense heat for up to an hour. The secret ninja stuff sits inside a large teabag, which in turn is kept inside a waterproof pouch. To make things steamy, you simply remove the teabag from its pouch, stick it into the green mug and add 100ml of water – any water, clean or dirty. The teabag then takes 20 seconds to start reacting at which point it soaks up all the water and starts bubbling away.

The components of the prototype flask

To make your food or drink hot, you then place the stainless steel beaker inside the green mug, pour in your cold beverage and seal on the lid. Oh, then amuse yourself for a few minutes watching steam rise like some sort of Hogwartian magic.

The whole flask is covered by a neoprene cosy (the one pictured isn’t the finished item) which protects your hand from the heat and makes sure the energy goes to your food.

I’ve used the flameless cooking flask on a number of occasions now and am dead impressed. I’ve warmed up some delicious Look What We Found Chicken Soup within a couple of minutes, and then kept it hot for well over half an hour as I forgot about it and played frisbee.

Two cups of tea… just!

I’ve also made coffee – the flameless cooking flask is perfect for this because it will get water to around 90C, which I’ve read is about perfect for coffee-making.

The less drowsy amongst our readers might now doubt the Flameless flask’s ability to make a proper cup of tea since it doesn’t boil. Well, I just tested that. I filled the stainless beaker up with cold water and popped in a Tetley teabag. After 6 minutes I had a perfectly good (by campsite standards) cup of tea. I wouldn’t have served it at the Ritz, but I’d be glad of it at 8am on a wet Sunday morning. I tried my luck with another full beaker of cold water, but alas I think I asked too much and ended up with a tepid tea ten minutes later. The results are much better if you go for two small cups of tea and use less cold water.

Steaming away again, with lockdown lid

The Flameless cooking flask is safe, compared to other camping cooking options. If you take a barbeque into your tent, you’ll die. A stove in your tent; you’ll die. An open fire in your tent; you’ll die. An electric kettle in your tent; come on… man up!

Once the initial bit of reaction water is soaked up by the ninja teabag, and the lid is clamped on, you can knock the flask over and not suffer spillage. I did wonder whether there’d be a dangerous pressure build-up from the heating soup/tea but the lid seemed to let out the pressure without leaking.

Using the flameless flask at a recent social camping ‘do’ it received a lot of interest from people with kids. Everything from warming baby-milk to safety in the tent was mentioned, which can only be a bonus.

Cost wise, the flask itself and the initial batch of 3 heatpacks is £20. A further set of 7 heatpacks is £10. So, this isn’t a bargain product. In fact, it’s kind of expensive, so it’ll be suitable for more as an ‘occassional’ use piece of kit. Mind you, I suppose that for everything else except the morning cup of tea you would be up and about and able to fire up a stove.

*The secret ninja stuff is quicklime, or calcium oxide. When it has reacted, you end up with calcium hydroxide, which is a non-toxic substance used widely in the food industry, so disposal is harmless and biodegradable.

SUMMARY: This is a very interesting alternative to cooking with a gas stove or fire. I’m genuinely impressed by how easy and clean it has been to use. It’s very lightweight and rugged, so perfect for short, one-man adventures, but also has a wider appeal to families or the terminally lazy. The only caveat would be the price of replacement heatpacks. Hopefully, as sales increase for Trekmates, this price will come down.

  • Philip Dorking

    I’ve been running a beta test on this and the cooking pot. I found the smaller 20g heating pack makes a VERY hot cup of coffee, but pushes the lid off the cup. It may be me, but the heating pouch being square doesn’t fit into a round cup holder very well. I also found I needed to increase the recommended amount of water slightly to get a full reaction with the pouch.
    Having said that, it’s a great system and makes soup and coffee in one cup (washing it in between of course …. duh!) without the need of a flask or stove.
    Definately a product to watch for the future.

  • Cath

    Great idea which does work, it makes a nice hot brew. It doesn’t boil the water but it is hot enough for tea and coffee. As it’s flameless it’s much safer than a naked flame in a tent and means you can have a hot drink first thing in the morning without even leaving your sleeping bag! (assuming you have a bottle of water in the tent!)
    It would have been helpful if the green beaker had a mark on to show how much water was needed as we had to guess the first time we went out with it, although after a couple of goes you get to know the correct amount.
    Overall, a fantastic idea that will get plenty of use.

    • stu theobald

      Hi Cath,

      Current plans are to include a water bottle that is premarked at the two levels needed for the heat packs. We did discuss the idea of a calibration line but decided this was a better option to cover both systems

      • Cath

        Thanks for your reply, a water bottle would be fine and solve the problem


  • Limitcamper


    I just bought the cook flask but there seems to be a problem.

    If i try to pour the hot coffee or whatever in a seperate cup, the water from the bottom which was filled in for the heatpack streams out too and ruins the coffee.

    I used 40ml of water for the high power heat pack, like its told in the manuals.

    Maybe you have an idea whats the mistake.. or dont you move the bottle after heating?

    • Limitcamper

      i kept the lid on top and tryed to pour thru the lidhole

      • Hi. I have asked Trekmates to get back to you.
        Personally I pour off the excess water before pouring out any drink. That seems to work OK.

    • Sarah at Trekmates


      We have done some further tests to check the calibration of the measuring bottle (I assume you are using the bottle).
      The print of the measurement on the bottle is a little over 40ml, more like 45ml. If you fill the bottle to just under the mark there should be very little or no leakage of activation water from inside the outer cup.
      We are going to look at how we make this bottle in the future to see if it can be molded rather than printed to avoid any possible print errors caused by movement in the print process.

      I just wanted to say thank you for the feedback, this all helps when we develop and continue to improve products in the future.


      • Thanks for the comprehensive reply Sarah.

  • Herve

    Thanks for the review and comments.
    I’m interested in the Cook Box ( which works the same way as the flask, but I wonder: after adding the water and closing the lid, can the box be placed back in my backpack so I can resume hiking while the food heats up?
    I’m concerned about leaking liquid and/or steam that could make my other items wet.
    Advice from Trekmates would be welcome.

    • No, the box has to remain flat or you’ll get a leak.