Gas cartridges: which ones are the best and how much gas is left?
Cooking with gas is one of the most popular ways to heat water or prepare a meal while trekking. Besides being easy to use, it requires very little: a gas cartridge, a burner and some matches or a lighter. But which gas cartridges do you need to buy and how do you know how much gas is left in a used cartridge? You will get the answers to these and many other questions in this article.
Content of this article:
How much gas is left in my used bottle? (Measuring method for home)
How much gas is left in my used bottle? (Measuring method for in the field)
What type of connection do I need?
One of the most important things to consider when buying gas cartridges is the connection of the stove to the cartridge. In any case, most of the stoves that are available in our outdoor shops have a screwing mechanism for the gas cartridge, as opposed to the click system of Campingaz. So pay attention to this when buying, because in all countries - except France - screw-on cartridges are easier to find than those with the click system of Campingaz. More technically, we call these threaded or non-threaded gas cartridges.
Either way, both connections have a Lindal valve that seals the cartridge after disconnection from the burner. This is in contrast to puncture gas cartridges which are not suitable for use on a hike, because once punctured you cannot remove the burner until the cartridge is empty.
The thread on the MSR gas cartridge (left) and the Campingaz click system (right). You will find gas cartridges with a connection like MSR's much more often than the ones from Campingaz.
How much gas is left in my used bottle? (Measuring method for home)
To find out how much gas is left in a used bottle, the most accurate way is to weigh the gas cartridge with a kitchen scale. Gas cartridges always contain around 100-110, 230 or 450 grams of gas. If you know the total weight of your cartridge (you can look it up in the last column of the table below), you can calculate how much gas is left with a simple calculation.
Suppose you have an MSR IsoPro cartridge of 227 grams (this is the amount of gas) that you have already used several times. The scale indicates 250 grams. The tare weight or empty weight of the cartridge is 143 grams (370 total weight - 227 gas weight). Now subtract the tare weight 143 grams from the 250 grams weighed, so 250-143=107 grams. This leaves 107 grams of the original 227 grams and thus a little less than half.
How much gas is left in my used bottle? (Measuring method in the field)
Another method of checking how much gas you have left when you are out and about is to put a full and an empty cartridge in water beforehand (i.e. at home). You make marks to where the water reaches with both the full and empty cartridge. You then transfer these markings to the used or unused gas cartridges that you will take along on your trip. This way, you can keep an eye on how much fuel you have left during your trip and you can check this at any moment as long as you have water available somewhere (a lake, pond, calm watercourse, etc.). MSR has put markings on its two smallest models of 110 and 227 grams, so you don't have to do the preparatory work at home.
Which gas in which conditions?
When you buy a gas cartridge, it seems as if there is actually no gas in the cartridge, but a liquid. Actually, this is a gas that has been compressed into a liquid. If this compression would not take place and there would only be an airy gas in the cartridge, you would only have a fraction of the volume of gas available to burn. Every kind of gas has a certain boiling point, at which the liquid evaporates and thus becomes a real gas again. Outdoor gas cartridges contain a mixture of propane, isobutane and/or butane.
Of these three gases, propane is the best choice in freezing temperatures. Propane evaporates at -42°C, which means that it evaporates at all temperatures above and can therefore be used for combustion. The fact that a gas cartridge is not only filled with propane has to do with the enormous vapour pressure of propane. If you would like to take 100% propane with you on a hiking trip, you will need a heavier cartridge that can withstand this pressure (the smallest propane cartridges weigh about 950 grams) and a heavier gas burner that is able to handle pressure. The normal outdoor gas cartridges, which are made to an EN standard, can handle the pressure of smaller amounts of propane. Usually, the proportion of propane will vary between 20 and 30%.
The mixture is supplemented with isobutane and/or butane (also called n-butane). Isobutane is, if you like, an improved version of butane. Isobutane has a boiling point of -12°C, which means that it can evaporate up to that temperature. Butane, on the other hand, has a boiling point of about 0°C. At freezing temperatures, butane retains its liquid form, will not evaporate and so no combustion can take place. This gas is therefore not suitable for winter hiking.
In the table above, I have listed the gas mixtures per brand. As you can see, there are brands that use 70 and 80% butane, which is not very useful in the winter. It is not because propane is present in the mixture that a propane/butane mixture is suddenly good for temperatures below freezing. On the contrary. The proportion of propane will simply be burned up and suddenly, despite the fact that there is still gas - in this case butane - in the cartridge (the liquid that you hear when you shake it), you will get a weak flame that eventually extuingishes. Therefore, in light freezing temperatures, always choose a mixture of propane and isobutane and try to avoid butane. You should therefore choose gases from Primus (Winter or Power Gas), Jetboil, MSR or GSI. During the summer months, however, a mixture with butane is not a bad choice and you can use Summer Gas from Primus, as well as gas from Coleman or Campingaz. The cartridges from Edelrid and Optimus are also good at temperatures well above freezing.
In case of extreme freezing, the propane/isobutane mixture will not do. As mentioned, isobutane remains in a liquid state from -12°C and is therefore unable to evaporate. And propane has its limitations because of its enormous vapour pressure, so you do not have small, light cartridges with 100% propane.
Know that almost all gas cartridges available in Europe come from the same factories in Korea, regardless of the brand. Campingaz is one of the exceptions to the rule, made in France.
How much gas will I need on my hike?
To answer this question I assume that you are not going to prepare whole meals, but only want to boil water for a hot drink or to add to freeze-dried meals. Before you can make any calculations, you need to have a nutrition plan. You need to know when you will eat or drink what and how much water you need to bring to the boil for that.
For breakfast I eat a couple sandwiches and drink a 25cl (250ml) cup of tea. At lunchtime I eat a freeze-dried meal for which I need 450ml. For dinner I need 400ml, along with another cup of tea (250ml). So for this one day I need 250 + 450 + 400 + 250 = 1350ml or 1.35 litres of water to boil.
This is an example for one day, but of course I make the same calculation for every day I walk. Then it is important to know the cooking time and the burn time of the gas burner, as well as the contents of your gas cartridge. For the Optimus Crux Lite that I have, I find on the manufacturer's website that it is 3 minutes per litre and a maximum burn time of up to 90 minutes with an Optimus gas cartridge of 230 grams. So that means that theoretically I can boil up to 30 litres of water (90 / 3). If I were to use the 1.35 litres from my example every day, then theoretically I would be able to use it for 22 days (30 litres / 1.35). However, a manufacturer does not take into account variables that can drastically influence the gas consumption, such as the outside temperature, wind and altitude. That is why the description says "up to 90 minutes", because in reality it is significantly less. Usually, I can boil about 20 to 22 litres with a 230-gram cartridge if I use my wind screen.
A few more tips
If you set your burner to maximum output, the gas cylinder can feel very cold and in some cases can even freeze a bit. Normally, the gas mixture is warmed up by the outside temperature. That heat is needed to convert the liquid into gas. If you heat water on a low fire, this will be less of a problem. But at maximum output, that heat does not have time to warm up the mixture. This causes the liquid to cool down. If this cooling is too great, the burner can no longer work efficiently and the flame can even be extinguished. When it is cold it can occur even more often. Therefore, keep the gas cartridge warm - before use - if you want to use your burner efficiently in cold conditions. You can put your cartridge in your sleeping bag or jacket beforehand. Another possibility is to immerse the cartridge in water. As long as the water is not frozen in freezing temperatures, it is still warmer than the outside air.
It also follows from the above that if you open the burner fully, it works less efficiently than if you keep the flame a little smaller. To further optimise gas consumption, it is best to use a wind screen. If you don't have one, choose a sheltered spot, out of the wind. Also use a lid on your cooking pot so that the water vapour and thus heat energy are retained.
It is sometimes said that a gas burner does not work well at high altitude. The problem is not altitude but rather the outside temperatures, as previously mentioned. However, the higher you go, the lower the boiling point of water and therefore the longer you need to cook something. For example, at an altitude of 3000 metres, water will already be boiling at 90°C. If you then add water to your freeze-dried meal, you will need to let it 'soak' a little longer to compensate.
Each new gas cartridge comes with a plastic cap. Keep that cap. It prevents dirt from getting on the thread of the cartridge and damaging the mechanism of your burner. As an added bonus, you also prevent corrosion (rust) of the thread and valve if you keep the cartridge in your cooking pot.
One final note: refilling gas cartridges is possible, but is strongly discouraged by the manufacturers. So do not do that unless you are 100% sure of what you are doing.
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