I’ve taken several multi-day trips this spring and summer with a Jetboil Stove, which like many lightweight stoves runs off canisters filled with a blended isopro fuel, and each time I pack I’m faced with the needling question of how much fuel is left in those partly used canisters that are accumulating in the basement. Can I get by for the weekend with one partially used canister or should I carry a spare just in case? Invariably I carry the spare because I can’t accurately guesstimate how much longer the partial will burn.So the question that keeps running through my mind is this: Are there accurate methods of determining how much fuel or how much burn time I’ve got left in my canister?
I just ran across two solutions listed on Backpacker’s website quoting Steve Grind, the product manager for MSR stoves. Here’s his advice:
“There are a couple of reasonably good methods for determining the amount of fuel remaining in the canister. The most common one is to weigh the canister when it’s full and write that number (in grams or ounces) down onto the canister itself. After the canister has been partially used, it can be re-measured and the weight difference is how much fuel has been consumed. The net weight of fuel in a full canister is printed onto the canister, so you can calculate the percentage used and the percentage remaining. To get to burn time remaining, you’ll have to know the burn time specific to your stove. We publish burn times per canister for each of our canister stoves. So if you have 60% of your fuel remaining, and the burn time on a full canister (again, specific to your stove) is 80 minutes, you have roughly 48 minutes of burn time remaining. These burn time numbers really need to be taken with a grain of salt, though, because canister output is going to vary dramatically depending on conditions.
A more useful measurement is the number of liters of water boiled per canister. For example, the MSR Reactor boils about 22 liters of water per full 8 oz. IsoPro canister, so a half-full canister will give you about 11 more boiled liters. The other method of determining the amount of fuel remaining is much easier to do in the backcountry, or in your kitchen if you don’t have an accurate scale at your disposal. The canisters will float upright when placed in water, and the water line will vary depending on how much fuel is remaining in the canister. If you float a full canister and then float an empty canister, you can measure those water lines and mark them on your new canisters, then re-measure after the canister has been partially used. If the water line is halfway between the ‘full’ water line and the ’empty’ water line, the canister is half full.”
Here are three other tricks that may help you make better use out of a canister stove:
- Use a windscreen. The heavy foils screens that come with MSR gas stoves (like the Whisperlite or Simmerlite) work well. Wrap the windscreen loosely around the stove so there is plenty of room for air to get into the burner and for excess heat to escape. If you don’t have the heavy foil screen from a Whisperlite, make a screen from a double-layered length of aluminum foil.
- To improve the cold-weather performance of a stove, place the canister inside the the lid of a pot and pour in an inch of tepid or cold water. Even cold water is warmer than below-freezing air temperatures.
- For winter use, figure out how to hang your canister stove in a tent so that you don’t waste calories cooking outside in the cold. The ability to hang may even be a requirement of the stove you purchase if you’re a winter adventurer and/or a climber. Jetboil makes a hanging accessory for their stove that’s very slick, but I’ve also made my own hanging system for the same stove by sewing a loop of webbing onto the pot’s neoprene cover/cozy opposite the pot’s webbing handle. A hanging cord then runs between the webbing handle and my sewn-on loop (see photo below). When hanging the stove, I also twist a short length of bailing wire (4-inches long) between the burner and the pot to ensure these two parts don’t separate while I’m cooking. Having the burner fall off the pot would spell disaster for a tent floor (unless you’re using a floorless tent).