Winter Gas

My favourite stove for the winter months in Scotland where overnight temperatures may typically be down to -5C, or more infrequently below -10C, is the Kovea Spider. Having used this stove now for 4 winters I’m happy with both the performance & reliability.

As mentioned previously I carry a pricker & tiny spanner to be able to clean the gas nozzle should it block, the most probable ‘failure’ mode. More recently I’ve taken to also taking along the BRS-3000T canister top stove as a back-up,  not the most efficient of stoves & susceptible to the wind but it will provide me with a hot meal & at only ~28g it serves to guard against something like a hose leak on the Kovea.

Another precaution I adopt is to check the sealing of the Lindal valve on the canister as I disconnect the stove; it’s no good have 2 stoves without fuel. I’ve only ever experienced one canister leaking but it takes 2 seconds to check & if leaking stove could be reconnected.

On a recent trip I was questioned why I ran the stove with the canister inverted even with the bothy being above freezing (3 or 4C) in the bothy. Well here was my reasoning, it’s all down to physics/ thermodynamics, which I hope to put across simply.

The Primus Power 230g gas canisters I tend to use in Scotland contain a blend of gases (25% propane, 25% isobutane and 50% n-butane) which in my experience work fine with an upright canister (aka canister top stove) down to +5C without any intervention, like warming the canister.  Below this the evaporation rate of the n-butane (-1C boiling point) will slow, & eventually stop. This will result in only the propane (-42C), isobutane (-12C) being available for fuel & eventually a half full canister that doesn’t work.

Why the +5C ‘limit’ when n-butane’s boiling point is -1C? The liquid gas needs energy to evaporate (boil), similar to trying evaporate a pan of boiling water, the energy is supplied by the cooling liquid within the canister; the lower the temperature the lower the evaporation rate of the n-butane will be or it may completely stop. One solution would be to use a different gas mix; the slightly more expensive Jetboil canisters with their 80% isobutane & 20% propane mix should operate satisfactorily down to -6C; I prefer to just flip the canister.

One thing that has always bugged me is the collection of part used gas canisters. I’d thought about getting one of the G-Works Gas Saver devices that allow the decanting of part used canisters into one but the £35 price put me off (the cost of 8 full canisters) so I’ve ended up just using the ‘empties’ for car camping or the occasional overnight trip.

Then I found the Jeebel Adapter, at ~£6.50 it seemed worth a punt.

I’ve now successfully decanted several ‘empties’ canisters into one without any issues. The recipient canister had been in the freezer overnight, the ‘donor’ canisters got stood in hot water for 15mins (to increases the pressure differential). It only took a minute to decant all but ~10g of gas out of the donor canisters (no liquid left on the canister). I did weigh each canister beforehand (nominally 150g empty & 380g full) ensuring there was sufficient space in the recipient for the transfer so as not to overfill; if over fill does occur the easy solution would be to immediately burn off the excess.

It’s worth noting that if using a canister top stove close to freezing the ‘empty’ canister contents  may be predominantly n-butane, for the reasoning above, so the resulting ‘full’ canisters would be best reserved for warmer weather; inverted canister use avoids this to a large part.