By Jörgen Johansson
Jörgen: Roger, as you know from my article the ground rules are deep cold and two fairly similar stoves. Both have a burner on legs and a hose connecting the burner to the fuel container. The containers are filled with butane/propane mixes or white gas/petrol. No top-mounted gas canisters. Of course the pots and windscreens should be identical and therefore of no importance to this comparison. And since I from my own experiences considera canister stove to be quite practical down to minus 18-20 C (provided I keep the canister in my pocket or sleeping bag when not using it), let's keep in mind that we are talking about temperatures below that.
To start with I listed six factors that I considered relevant for the comparison:
-Weight
-Fuel consumption/weight
-Ease of use (lighting up, shutting down etc)
-Usability in tent/vestibule-Mechanical reliability
-Works well even in extreme cold
I will ask you to comment on all these factors in turn, but first; would you like to comment on the selection? Have I missed some important factor?
Roger: Well, I would add user safety to the list..
Jörgen: Fine, I'll add it and we'll get back to it. Let's first talk about weight. To begin with let's look at the hardware. I've put down the canister as a winner, but the difference might not be that big. What do you say?
Roger: No hesitation here. There are quite a few stoves today which can take either white gas or canister, so the actual stove weight is the same. But the weight of a fuel tank and pump is always greater than the weight of a canister. In addition, you have to add the weight of cleaning and repair gear to the white gas stove - stuff you rarely need with a canister stove. Mind you, many white gas stoves are far heavier - compare the XGK with the almost any remote canister stove.
Jörgen: A comparison of canister and white gas stove weights would have to include fuel consumption and transport vessels etc, which means that one kind of stove could be lighter on short trips and another on longer. My own mpression is that, generally speaking, a canister stove comes out ahead. What are your experiences?
Roger: Well, the fuel tank and pump are always heavier than the canister. If you carry extra fuel you need an extra container of some sort. But there are several more factors here to consider. The first is that butane/propane mix has a higher energy content than white gas, by weight. What's more, in the field you end up using a lot more white gas than a simple calculation would suggest. Part of the reason for this is that you use up a surprising amount of white gas when priming the stove to get it going.
Another reason relates to the ease of relighting a canister stove. This means there is no hesitation about turning it off, while the hassles of restarting a white gas stove mean that users
often leave it running at low power even when not actually doing anything with it. Over all, it is quite common to find that white gas consumption runs between 50% and 100% heavier than butane/propane. That extra weight starts to add up over a few days.
Jörgen: OK, what about ease of use. To me the canister stoves seems toc ome out as winners. What do you say?
Roger: All I can do is laugh. The hassles of running a white gas stove compared to 'connect, turn on and light' with a canister stove make it a complete walk-over. When the canister stove has a piezo-lighter as well, the mismatch becomes ridiculous. Canister stoves are just so easy to use in comparison.
Jörgen: To me cooking inside the tent in winter is of paramount importance to my comfort. Both morning and night I want to be able sit in my sleepingbag with the stove beside me and melt snow as well as cook. My top-mounted canister stove has worked great for this. How do remote canister stoves compare to gasoline stoves in this aspect?
Roger: Oh, I hear you about sitting comfortably inside your tent! We often get bad weather up in the mountains here in Australia, and I always cook in the vestibule of my tent.
My wife lies in her sleeping bag further inside the tent and demands to be fed. This while the storm howls outside...
Let's first compare ease of use between a top-mount and a remote canister stove. Basically, there is very little difference between the two. In fact, one of the things I like about the remote canister stove is the fact that it is lower to the ground than a top-mount. Otherwise, it is still just 'connect, turn on and light'.
I had better add a point here about inverted canister stoves. Basically they are just remote canister stoves, but they include a preheat tube similar to that found on white gas stoves. (Not all remote canister stoves have the preheat tube: check!) The preheat tube allows you to start with a dead-cold canister and cook happily down to about -25 C. That is a huge advantage.
The only thing you have to do is to start the stove at a low power for maybe 10 - 20 seconds - but you can start the stove with the pot already on it. In many cases you can start with the canister upright and then invert it after that time.
One really major advantage of remote canister stoves is that the operation inside the canister is quite different. With an upright canister the energy used to vaporise the fuel come initially from the liquid gas inside the canister. As a result the liquid gas cools down, possibly to the point where it no longer evaporates enough to drive the stove.
This can be dangerous in the cold. Even if it continues to work, the evaporation will be preferentially extracting the propane and leaving the butane. It is quite common for users to complain that their canister is 2/3 full but nothing is coming out of it. Butane boils at -0.5 C: if the propane has been used up and the butane is sitting at -5 C, you have a dead canister.
But when you invert the canister the evaporation of the liquid happens in the preheat tube at the stove, using energy from the flame. The canister does not cool down. The pressure used to
drive the stove comes from the static vapour pressure of the fuel in the canister - a pressure which stays constant as the static vapour pressure stays as constant as the temperature.
The other really major advantage of the inverted canister stove is that the fuel extracted from the canister is the original liquid butane/propane mix. This means that the percentage of propane left in the canister stays constant, all the way to empty. You don't end up with a canister 2/3 full of non-boiling butane. In effect, the propane provides the driving pressure which is given by the pump in a white gas stove.
Jörgen: Another factor of importance in deep cold is mechanical reliability. Are there screws, gaskets, springs and stuff that can fall out or break? Is it recommended to bring tools and spares? Fixing stuff like that in bitter cold is not what I want to do. It seems to me that the canister is a simpler construction with fewer things that can go wrong. What do you say?
Roger: Servicing a stove as the sun goes down and the temperature drops way below freezing can be a bit worrying. I've done it for both sorts of stoves. In the case of the white gas stoves it was always a messy job. I was not always successful either, so it was biscuits and chocolate for dinner.
In the case of the remote canister stoves I have serviced in the field it was all pretty simple. I removed the valve and wiped it clean and screwed it back in place. Then I removed the jet, cleaned it with a proper little bit of jet-cleaning wire (a careful poke and a wiggle) and replaced it. That took only a couple of minutes and then we had the stove roaring away for dinner. But having to service a canister stove in the field is pretty rare in my experience.Jörgen: You wanted to add safety for the user to my list. What are you thinking of?
Roger: I've used many white gas stoves in the past and been rather close to some scary incidents. I've lost parts of a sleeping bag and a pack when someone else mishandled white
gas, a long way from civilisation. I've seen the safety valve on a stove release and a huge flame shoot out of it. I know some people who ended up with huge amounts of plastic surgery after a white gas tank exploded. So white gas frankly scares me a bit. It's even worse when you are clumsy with gloves on. I don't see canister stoves presenting those sorts of risks.
And that does not cover the risks of starting a stove in a tent. With a canister stove there is no flare-up at the start, so you can light one even in a small vestibule or even an emergency bivy quite safely. But priming a white gas stove can easily involve a fireball of flame - MSR actually mentions this with the XGK stove. Very few people are willing to risk that inside a tent vestibule! But if there is a howling storm outside or you are in an emergency situation, your options are not great.
Jörgen: To sum it all up; since the issue for me is not if canister stoves work in winter, which I already know that they do provided you keep the canister reasonably warm, but will they work in really, really deep cold. Can I trust them to melt my snow and boil my food under almost any circumstances. On this I give the victory to the gasoline stoves out of, Iguess, tradition and hearsay, since I haven't tried any of them in bitter cold. What do you think?
Roger: That's a lot more complicated. A standard 70% butane / 30% propane canister will give off fuel down to -25 C. An 80% iso-butane / 20% propane canister is almost as good. Canisters with less propane are not so good, and should be avoided. (They are aimed more at the family camping market.) But what matters here is the temperature of the fuel in the canister, not the ambient temperature. As you have indicated, if you can warm the canister up beforehand then you can use it to considerably lower temperatures.
The next thing to consider is how you run the stove. If you put the canister out by itself sitting on the snow it is going to drop down to ambient fairly quickly, and that could kill the stove. On the other hand, if you insulate the canister from the snow and let it pick up a bit of radiant heat from the stove - through a gap in the windshield for instance, then you can keep the contents warm enough. Obviously you do NOT let the canister get too hot for safety reasons, but as long as you can put your hand on it (ie <40>
If you are going to be travelling at -30 C for some time you will inevitably be carrying more gear than a summer walker. You may well be using a pulk or sled to carry some of this gear, and that allows you to carry a bit more weight. At the same time, finding water is going to be more difficult, so you may need to melt a lot of snow. Doing so can literally double your fuel consumption. Under these cold condition it may be worth while considering the use of small LPG containers such as those made by Coleman. These containers hold a larger weight of fuel, and the LPG or propane will work down close to -40 C - without being warmed.
Anyone contemplating travelling below -20 C should be careful to test their stoves and other gear fairly thoroughly close to home. Grease and O-rings may need to be changed for these temperatures. Cheap O-rings can go very hard and leak at -20 C. Viton O-rings are good between -26 C and +200 C, Nitrile O-rings are good between -40 C and +105 C, and PU
O-rings are good between -50 C and +105 C. It's a pity that Viton cannot go lower in temperature; the +105 C upper limit for Nitrile and PU is really a bit low for safe use near
the stove. (But these materials are OK when used on the remote canister connection.) More esoteric rubber are available - at a price.
Many plastics can shatter at the lower temperatures, and can be even more fragile if they have been soaking in fuel for a while. That applies especially to plastic pumps in fuel
tanks: you may need to change them to all-metal ones. I have heard of some pumps reliably disintegrating below -20 C. Below -40 C is (to quote a friend) 'freaking cold'. It requires extremely specialised gear and skill, and I don't have enough experience there to comment.
Jörgen: By the way, all the photos show a Powermax canister från Coleman. Does this mean that those are the only ones that will work under the circumstances you've described? As you're probably aware, Primus and Optimus are Swedish companies and very popular here.
Roger: N-butane is n-butane, iso-butane is iso-butane, and propane is propane.
Lindal valves are Lindal valves from Lindal Group (except for Chinese rip-offs) Canisters are all US Dept of Transport (DOT) approved.
The only thing that matters is the fuel composition - eg 70% butane / 30% propane. There are small variations in the odorant used, but they all have to meet DOT specifications. The reality is that the paint and the brand on the outside of the canisters means NOTHING.. Most canisters of gas are made and filled by one (or two) companies in Korea. That includes Primus. I am not sure who fills the Powermax canisters though - possibly an American company.
Most stoves are made by one Korean company or one of a couple of Chines companies, and that does include Primus and Optimus. And of course, the Chinese rip off the designs and sell clones real cheap. The clones do sometimes have bad variations though.
Jörgen: Thanks Roger. I'll have to sit back and digest all this for a while and weigh my different options. I hope to give my conclusions in an upcoming article soon. And anyone that wants to dig deeper into the tests and research Roger has done on stoves should check at http://www.bushwalking.org.au/FAQ/
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