Good evening Mr Kirkpatrick,
I have a question regarding the optimal size (volume) for a cooking pot for melting snow on a multiday alpine-style climb which includes bivis in a tent or in the open.
I always thought the more volume the pot has, the less time and fuel you have to use to melt enough snow for drinking and cooking instant food. I also thought that this would outweigh the weight penalty of the bigger pot because the more often you have to melt pots full of snow, the less time you have to rest or sleep.
Or is melting snow in smaller pots so much faster?
I was a bit surprised because I have seen that many three-man rope teams in the high mountains only carry an MSR Reactor with a 1.7l pot (like Tom Livingstone and his partners did during their Latok ascent).
Btw. I love the Down book, so much attention to detail!
Thanks for your question. Rather than give you a tight and formalized answer, here’s a bit of a brain splurge on stoves!
Snow melting is a subject a little like cooking pasta; some people just throw the pasta into some cold water in a pan, crank up the heat, and cook it until it looks cooked, while others, they will add the pasta to salted boiling water, along with some olive oil, then remove it while it’s al dente, add some more salt to season, and a tablespoon of olive oil, then serve. Which one is best? Well, at the end of the day, both the imperfect and perfect methods give you a plate of pasta; only one is perfect, the other less so (but only a pasta Nazi can tell).
So it is with snow melting, you can be a snow melting Nazi and treat it like pasta, or a does-it-really-matter, slack Harry. Both work and will produce water – but – when the chips are down, or the pasta, say you’ve only a thimble full of fuel left, or need to brew up that life-saving cup of tea below the summit of Everest, then being a Nazi might help.
The key point of snow melting is both the volume of snow to be converted back into water per unit of fuel (fuel efficiency) and speed of production (time efficiency).
If you’re sitting on a 100-gallon fuel drum at a basecamp, you can just read to the end of your Dan Brown chapter as the water boils away, as neither fuel nor time efficiency is important, and stressing over a 60 second boil time difference, or 5 milligrams of white gas, versus 5 milligrams of kerosene, is just another form of wastage.
But, if you’re perched on a ledge in your sleeping bag, in a winter storm, with just an egg cup of gas left in the canister, and every second spent cooking exposes you to the cold of the night, then your life might depend on seconds and milligrams of fuel.
Somewhere between the two would be a three-person team at a high camp, resting before they are going for the summit, with rationed food and fuel, but who have to maximally hydrate.
Added into these efficiencies are size and bulk, and weight, important if you only have a 30-litre pack, but less so with a pulk or jeep, plus safety concerns about the process (dangers of both gas and petrol stoves).
The BTU trap
Very often, people get sucked into the BTU (British thermal unit) trap, wherein they simply judge a stove by just its BTU score, as in, an MSR Reactor (9000 BTU) must be better than a Jetboil Jetboil Zip (4500 BTU), or that both are trumped by an MSR Wisperlite (9500 BTU).
You will find hundreds of Youtube videos of people in their kitchens doing tests in which they boil a litre of water with X stove in order to prove it boils water faster than Y. This is a mistake.
Just as a Ford Mustang might appear to be better than a Ford Mondeo, when your aim is getting from A to B, five days a week, for the life of your car, why pick a car that increases your risk of dying fourfold, even if it’ll get you there a few minutes faster? Yes, it’s easy to produce a very fast car, but for what you gain in speed, you might lose far more (in the case of a Mustang, that might be your life).
Put it another way, a Falcon space rocket produces 109,941,300,000 BTUs, but it can’t do it for long, plus it’s crap at making a nice cup of tea. A humble Trangia, on the other hand, pumping out a pedestrian 3500 BTU, will do so pretty much forever (as long as you add spirit every half an hour).
And so, it’s best to see BTUs like you do the top speed of a car, and work out if you’re thing is formula one, or driving from London to Cape Town; generally, it’s the latter.
Before I go on, I’m going to break stoves into three tiers, as as to help you better understand how to get what you want:
- Tier one: Summit stoves.
- Tier Two: ABC mountain stoves.
- Tier Three: Static camping or basecamp stoves.
Tier three Stoves (Basecamp stove)
I’ve lived in several places which had either single, double, or quad gas rings hooked up to a large gas bottle (4kg to 50kg propane). This could be a stand-alone iron stand burner that was just about indestructible or a tabletop kitchen burner, like a cooker top minus the oven.
This kind of stove is pretty much the standard kitchen set up for the majority of people on the planet, well, at least those who have progressed from wood or dung fires.
In terms of utility and function, this kind of stove cannot be beaten. You can just turn on the rings with a match and easily turn the flames up or down to boil or simmer, with the gas lasting for months or years on end (they also work during power cuts!). If you’re a car camper, instead of taking along a Jetboil or MSR, this is what you really want.
Such a stove will allow you to vary the BTUs, like any kitchen stove, ranging from 400 for simmering to 18000, or even higher for specialist stoves (25000 BTU).
The burners on such stoves - not camping stoves - are also designed to handle medium and large and extra-large pans, having much broader flame patterns (they don’t work well with your little titanium camping mug). This allows you to cook large meals for many people far more easily than juggling big pans on small camping stoves.
Such stoves also allow enough room to be boiling water on one ring while running a large wok or frying pan on another. They are also dirt cheap because the customer base is skint (that’s why Aga cookers cost the same as a car). This means it’s possible to run multiple burners at a low cost (you can buy a single cast iron burner unit for around $50, or even cheaper).
Although this style of the stove is not going to be carried in a pack, it’s the ideal heavy-duty base camp stove, with its multi burners being perfect for both melting snow in large pans (10 litres plus), but also maintaining a rolling boil or simmer (although generally, you would transfer water into large flasks).
So, if you’re running a basecamp kitchen, cooking and melting snow for dozens of people, this is the kind of stove you’ll use, not a dozen jet boils, as you will really not have to think hard about either speed or fuel efficiency as long as you’re sensible.
Tier Two Stoves (ABC Stove)
So you can see there are some great things about a tier-three set-up, but that’s not the kind of trip you’re going on. You’re not going to take such a system on a plane (but rather buy or rent in-country) or carry it in your back, but rather get dropped off with it (or carry it in a vehicle).
Yes, you’ll be camping and will be out in the wild for an extended period – so not survival/alpine style cooking – but you need a portable option. And yet you still want to have some tier three functionality, such as to be able to bring along a multi-week/month supply of fuel, cook with both small and large pans, and both cook complex and simple meals, plus melt snow.
When working through your options for such a trip, you should always nail redundancy first, because although a broken Jetboil might force a sad retreat down a climb, a broken stove – when it’s the only one you have – on a remote glacier, far from rescue, might be far more serious (you’ll end up having to burn your ropes to melt snow to survive until pick up!).
This means you need two stoves system at a minimum for a two-person team or one stove per two people (so a two or four-person team would have two stoves, while a six-person team would have three). Don’t forget that having two stoves does not mean you don’t need to look after them as you would one (and know how to do that), meaning you need a repair/spares kit, at least one spare pump, and multiple fuel bottles (if you stand on your only fuel bottle with your crampons on you’ve had it).
Next is fuel. You do not want to use gas cartridges for a tier-one stove due to both bulk and cost, as well as sturdiness, meaning a liquid fuel (either white gas or petrol) is your best only option.
With all liquid stoves, you need a method of carrying gas that is 100% leakproof and robust, especially if you’re going to abuse your containers physically or environmentally (note that plastic gets fragile in the cold and can shatter). Also, remember that most fuel containers are designed to hold fuel on a shelf, not inside a pack or pulk.
As a side note, the British lost around 25% of their fuel during the North African desert wars during WW2 due to using poor quality fuel containers made from tin, which was poorly designed, being only single use. This problem was only partially remedied by adopting captured multi-use German “jerrycans”.
Personally, I think it’s best to bite the bullet and carry all fuel in MSR fuel bottles (I own about 27!), as this pretty much guarantees fuel security but also removes the problems of filling bottles. If you are filling bottles, then make sure you take along a funnel, ideally one with a filter, as this will stop rust and cockroaches getting into your bottles (also, never place your fuel anywhere near your food!).
If fuel bottles are not an option, then small or even large fuel containers for cars (orange plastic 5-litre ones, or 20-litre metal jerrycans) work, but not that the more fuel you carry in a single container, the more fuel you lose if something happens to it (stolen, falls over with lid off, gets contaminated etc.).
The expedition default these days is generally the MSR Wisperlite or XGKII stove, but my personal choice would be the Wisperlite due to it being much easier on the ears and has the ability to simmer (I would add in simmer ring as well). Some people will say the XGK is the better expedition stove, but I used my Wisperlite (until it was stolen), pretty much every day for two years, from -50 deg to +50 deg, sea level to 17,000 feet, and it never let me down (note, at super cold temps you need to sleep with fuel pumps to avoid fuel leaking out, which also affects the XGK).
Such a two stove system can be used to set up a great base camp kitchen when used in conjunction with a wooden cooking board, and both stoves can be used together under a large pan if speed is crucial (this might be important in a large team).
When weight becomes a factor, you can take one stove and have the advantage of not having to stress about cold or a loss of pressure. Such a stove is also much improved, both in pan stability and fuel efficacy, but most of all CO2 avoidance, if you build a windshield/pan support (think Trangia set up).
As for pan size, all such stoves are limited by the size of the flame, and a very large pan (10litres), will only really work when used with two stoves (make sure this set-up is stable), and so I would not use a pan larger than 2.5 litres, or 20 cm wide, as you will begin to lose efficiency.
One last point is fuel consumption, of which there is a lot of conflicting advice. The amount you need to carry depends on many factors, including the obvious (assuming you’re looking at milligrams per person), such as altitude, temperature (do you get water from a tap or steam, or from snow and ice), and type of food you’re cooking (fresh or dried, pasta or brown rice). But you also need to ask if your consumption is casual or calculated, as it’s easy to spend a rest day brewing up endless cups of tea and fried egg sandwiches and use a litre of gas while on a route you could get away with just a tenth of that.
As a baseline, for calculated summer use, go with 120 ml of white gas and 200 ml for winter/expedition, and if it’s casual, it doesn’t matter as you’ll no doubt be near a gas station. This 200 ml figure can be reduced by maybe 30% if you use a high-quality windshield, heat exchanger, reflective stove board, and employ a single boil strategy (you only run the stove once a day and employ flasks for breakfast drinks).
As for snow melting, if you try using a 10-litre pan filled with snow versus a 2.5-litre pan, you may well find that the 10-litre pan is easier and less time consuming (for you) to monitor; just keep adding in snow and allow it to melt, but in terms of fuel and time efficiency, carefully monitoring a 2.5-litre pan will be better. This would be doubly so if you also want to melt the snow and then boil it, as I think it would be far faster to do this four times with a 2.5 pan than once with a 10-litre pan because high volumes of water on medium BTU stoves will often reach some equilibrium where the water is cooling faster than it can heat up (add a second stove and you mill move this point).
On the subject of melting snow, one of the most important points to make is that your snow melting /water boiling pan should never be used for cooking. Doing so will introduce food particles that will contaminate your water and make it taste foul. This is most common when someone just fills a pan up to the top with snow and just sticks it on a high flame. What happens is the snow in contact with the base of the pan melts and then partly evaporates, leaving bare metal that superheats, and burns any food particles, making the water undrinkable. Contaminates also include coffee, tea or sports drinks. Separate out your cooking pan(s) from your water pan.
Tier One Stoves (Summit stoves)
This will generally be a single stove, unless you’re concerned about having to bivvy apart (the weight of the burner on a Jetfoil style stove is minimal if each climber is using the pan part as their personal mug/pan), and can be a canister or liquid fuel, depending on the length and consequence of stove failure (a canister stove has a higher failure rate, and most faults cannot be fixed in the field).
Here it’s important to focus on this one-pan system and keep your pan (you will generally only have one) only for water; adding this into a cup of dehydrated food bags (an empty and clean dehydrated food bag makes a good lightweight bowl).
A great story to illustrate this point was Colin Haley’s solo of Mount Hunter. Being very thirsty and dehydrated, with little gas left, he stuffed his Jetboil stove with snow and just cranked it up and waited for it to boil. Unbeknownst to Colin, the remnants of his last meal in the pan just turned to carbon, creating a foul-tasting and undrinkable slushy, meaning he was not only out of gas and water but also had a mouth full of foul poison (this is typically the reality of doing a Bear Grylls and drinking your piss).
Tier one strategy
Really your question here is about using a tier-one stove in a tier-one style stove scenario.
On most climbs, when you’re using a tier-one stove, you will only have a small pan (depending on team size) and limited fuel, and so it’s best to do the following:
- When melting snow, try and get set up so everything is where you need it, as this will limit the chances of spilling all your heard-earned water. In a camp setting, this means having a bag for snow (Ikea carrier bag works), or a stuff sack (good for high camp), plus it’s good to have something clean to scoop in the snow, like a mug or jug (many plastic cups and jugs will break in the cold, and so a Lexan style cup/mug works best). It’s best to avoid just scooping up snow around you as this can easily the contained by all sorts of nastiness as people move around. On one climb a did, someone even ended up finding a toenail in their dinner!
- Try and always begin snow melting by priming the job with water. This can come from the remains of your day’s water ration (not if you’re using a sports drink). An alternative system (that will not work for alpine-style climbing, but rather polar style trips) is to employ a flask and always leave a little bit in the bottom to start the snow melting. This priming water will avoid the possibility of the super pan heating and burning, as well as generally making the job faster.
- So, if you’re using priming water or snow, I think it’s best to start with a few centimetres of cold water that can be heated to the start of a boil, and then keep adding in snow, which will instantly turn into water (and cooling the hot water as it does so).
- Now, if you’re trying to fill up your Nalgene bottles, when you’re got maybe 120% of the water needed, boiling if you want to use it as a hot water bottle in the night, or cold if you want to save fuel, transfer it over to the bottle, leaving behind that 20%, which will be the primer for the next batch of water. This approach will be much faster than trying to melt and heat up 2 litres of water, empty the pan, and start again.
- If you’re adding boiling water to food bags, again, cook 120% of what you need, add the water, and then melt more water while the food is heating up (place it inside your clothes for extra heat, and invest in a large plastic WeLoc bag clip, to avoid spills).
- It’s always faster to melt ice than snow, and so if you’re just about finished your stove duty, try and end up with a little bit of ice in the pan, as this will speed things up in the morning if you don’t have priming water.
The most fuel-efficient approach in a wilderness setting has to be weighed against a number of factors, some environmental, but other practical, maybe even cost. These include altitude, temperature, weight/bulk allowance, access to fuel, safety, both from CO2 and fire.
A good quality gas stove, with a brand new canister of gas, at sea level, on a summers day, will rapidly turn a bag of ice cubes into several cups of tea, and anyone testing such a stove before a trip to climb the Cassin ridge will no doubt be assured of their ability produce life-giving liquid to the team, both to hydrate bodies and food.
Now, once you get to 14,000 feet, with a half-full gas canister (your last), with a temperature below minus twenty, your integral sparker broken, and all your lighters wet, you might find you’re struggling to even produce cold water. If you’re lucky, you might be experienced enough to be cooking in a warmer part of the day, have a flint and steel, and using a Reactor or Jet Boil stove that is highly efficient, and employing a heat exchanger to counteract the cold (or simply just putting your hands around the canister).
An alternative to this summer sea-level test would be running an MSR Wisperlite with a full fuel bottle of white gas. As above, you’d rapidly turn those ice cubes into tea. Saying that, this set-up would no doubt lose points due to an MSR stove being a bit heavier and bulkier, and more expensive (due to it having to deal with raw fuel, which much is preheated etc., rather than compressed gas), and dirty, plus it’s not just a foolproof push-and-go option and requires priming (it requires a certain level of skill to use safely and effectively).
But transport that stove up to 14,000 feet, half a bottle of fuel, and cold, cold temps, and how does it perform? Well, just the same as it did in your kitchen.
The difference here, perhaps while perched on a tiny ledge, is which stove - irrespective of efficiency - has the greatest utility, irrespective of speed or fuel efficiency? I know of people who’ve used a Jetboil inside their sleeping bag, something you can’t do with an XGK!
Sure the liquid stove might produce a pan of boiling water, but priming it while it’s sat on your knees, and balancing a pan on top, requires a lot more skill than just firing up a Reactor.
A note on cold, hot and boiling water
A unit of gas or petrol will produce ten times more cold water than boiling and about five times as much hot water. This is an important point when you’re in a survival or fuel rationing scenario, as cold water has just as many calories as boiling. Where boiling water is the only acceptable end product is when heating dry food, although even here, you can soak dried food overnight in cold water in an emergency (you can also stuff the bag with snow and place it inside your clothing while on the move, or in a sleeping bag). Forging hot drinks can be tough on your team morale, but if it’s only for a night or two, it’s far better than the alternative, which is deep and debilitating thirst (made all the worse by being surrounded by water).