Liquid Fuel vs Gas Stoves

Regarding "Meths", Methylated Spirits: Meths isn't methanol, it's ethanol with stuff in it to stop you drinking it. Possibly some percentage of methanol and nasty bitter stuff and colour. Presumably made by fermentation/distillation so not a fossil fuel. Looking at a [spec sheet](https://colorex.co.nz/wp-content/uploads/2016/03/sds_tmk_ah_coloured_methylated_spirits_issue_5.pdf) for NZ sold Meths, it seems to be all (>99.9%) Ethanol with some Denatonium benzoate to make it nasty and bitter. Energy content is only 60% of White Spirits (30 MJ/kg vs 48MJ/kg), so you need more than half as much again for the same heating value. Butane/Propane are 49/50 MJ/kg, so similar/slightly more energy/kg to White Spirits. [Data sheet here](https://www.engineeringtoolbox.com/fossil-fuels-energy-content-d_1298.html) I tend to use a little homemade meths burner (two Redbull cans and a MSR style foil windshield) for short solo trips, I can carry 150-200 ml of meths in a plastic vanilla essence bottle or similar. Main advantage is avoiding taking and using just some of a full gas canister (or having to go out and buy same). I might take the gas canister if I had one 1/3 or so full lying around. Disadvantage of the meths burner is it's hard to adjust heat output, so hard to simmer say rice for 15-20 minutes in a small pot. Regarding Gas Canister stoves, I was camping up on the Annette Plateau on the weekend, melting snow. Kovea titanium burner screw on top of gas canister. It wasn't cold, maybe just zero overnight. It was clear the burner head was conducting significant heat down to the gas canister, also clear that gas evaporation was cooling the liquid Butane/Propane below ambient, my impression is that if you start with a body temperature canister, once it's going, it gets enough heat conducted down to keep it going as long as you keep it off direct contact with the snow. A universal fuel burner is also possible and easy to improvise if you run out of/can't get normal fuel, lose your usual cooker: Just the bottom 3 cm of a coke can or small tuna can, a wick of coiled cardboard or toilet paper or dry moss. A wrap around windshield of oven tray foil skewered with a tent peg holds the pot above the burner. Three rocks can also hold the pot above the burner if necessary. You can burn anything from vegetable oil to ghee to yak butter to narwhal or penguin blubber to diesel/jet fuel/kerosine/scrapings of candle wax from around the candle holders in a hut in one of these, it's a little sooty but not too bad. If you need to burn white spirits or petrol, fill the can with sand and then pour in the petrol. (Need to be a little careful with this last option, best outside on a gravel riverbank or similar, and take care lighting...)

If you need to burn white spirits or petrol, fill the can with sand and then pour in the petrol. (Need to be a little careful with this last option, best outside on a gravel riverbank or similar, and take care lighting…) Is there a story to go with this last comment?

Not really. It's reasonably well known the Commonwealth/UK troops in North Africa in WWII did a lot of their cooking/tea brewing by mixing petrol with sand in various metal cans. AKA a Benghazi Burner. I've tried it outside, the problem is it keeps going better and better as the petrol heats up, then it suddenly goes out and you can't add more fuel safely as the can/sand is hot. So it does work, but you have to judge the fuel amount and you wouldn't want to do anywhere except outside in a sandy/rocky/non flammable environment. A wick stove with cooking oil/wax/kero works reasonably well. A bit smoky, sooty and not as hot or efficient as a pressure stove, but easy enough to use as long as you have something to put over it to put it out when necessary. Pouring water on it when it's going well can be a bit spectacular. I've cooked/brewed up a few times in huts using a can/wick and wax from leftover candles, tea lights or cooking oil left in the hut when I haven't had enough fuel for the conventional stove.

Ian, it's not evaporation cooling the cannister (as such), it's the dropping pressure in the cannister as the gas is used. PV=nRT is the formula. Pressure x Volume is proportional to Temperature (n & R are constants). The volume of the cannister is fixed/constant so only pressure & temperature can change. As the gas is used & pressure in cannister drops, so does the temperature. Reflected waste heat from the burner (& pot base) does warm the cannister a little but, overall, the cooling effect is greater. This is (1 of the reasons) why cannisters can ice up while in use. I didn't know about the sand/petrol thing but it makes sense - but think I'll stick to gas :)

it's the dropping pressure in the cannister as the gas is used. Wrong. The contents in the canister are stored as a liquid at around 20psi stops the gas boiling. As gas is released more liquid boils equalizing the pressure. If we were to use a gas with a really low boiling point like hydrogen we would have to store it at huge pressure in order to get a decent capacity and the cannister would weight a ton.

Fair point, geeves - sloppy thinking on my part. Liquid fuel evaporates to replace the used gas, maintaining the pressure (at constant temperature). The pressure does drop - but as a result of temperature drop, not directly because gas is used. (assuming the ambient temp is less than the cannister) ... and, Ian, evaporation *is* the correct word (apologies). As the fuel is used, heat is pulled from the wall of the cannister to provide the energy needed to vaporise/evaporate more gas.

I have a primus omnifuel that I bought for a trip to Nepal back in about 2002. It burns just about anything. But, it weight ~600g, and is the loudest gas burner I have encountered anywhere. My deluxe pocket rocket by comparison is light and burns relatively quiet. The omnifuel just doesn't get to go on adventures anymore.