Modern canister stoves like the MSR Reactor work great and have deservedly become very popular with alpinists and ski tourers. The reason for this popularity is simply because they work really well. The Reactor for example is extremely fast (a key consideration when making coffee in the am!), fuel efficient and works well in the wind. However, the fatal flaw with the Reactor (and other similar stoves like the JetBoil) is the canister. A side effect of the ability to rapidly boil water is that fuel is drawn from the canister more quickly than more traditional stoves such as the Pocket Rocket. This results in the canister cooling (stupid thermodynamics) dropping the pressure inside the canister and, in sub-zero temperatures, will eventually cause the stove to stop working despite there still being fuel inside the canister. Big issue on those cold mornings or evenings!
So how do you fix this problem? Well, I have tried a few things. First I used to always have 2 fuel canisters on the go, one on the stove and one inside my jacket and under my shirt… not a great way to stay warm and eventually both canisters would be too cold to operate and I would be too cold to run it anyway. On my second try I ran some copper wire through the element of the stove and around the canister. That way when the stove is on it’s heating the canister right? Wrong. The wire is not able to conduct sufficient heat to the canister to do anything but wreck my gloves.
Alas there is a simple and elegant solution to this issue. Place the bottom of the canister in a small bowl with a bit of water. When this is done you can hear the stove instantly roar to full capacity. The idea is that the canister cannot freeze unless the water freezes (thermodynamics to the rescue). Therefore the stove runs at full capacity and efficiency regardless of the outside temperature. This also allows every bit of fuel to be drawn from the canister reducing the amount of fuel needed on trips. Just remember to keep cycling the water in the bowl or it will freeze and the whole system breaks down. Try it out on your next outing and you’ll be impressed!
PS. When it comes to the MSR Reactor I’ve found that the MSR Deepdish Bowl is the perfect companion. It fits snugly over the bottom of the pot (1.7 L) for storage and so doesn’t take up any additional room in the pack, it’s light and allows just enough room for water to surround the canister.