Mt. Whitney Portal Store & Hostel Forums General Mt. Whitney Portal Store Message Board Does Gas Have An Expiration?

You probably had a vapor lock on the line. No matter what you did, it wasn't going to help until you disconnected.

If I know it's going to be cold in the A.M. I put my canister or fuel bottle (depending on trip)in a sock and stuff it in my boot so it's ready to go in the morning.

You're pretty much on point, but there are a couple of things I'd like to refine.

First of course, cold doesn't appear to be the issue at all in this case. Richard has a brand new stove that he's trying to use in his kitchen. I'm assuming his home is well above freezing inside.

But in terms of gas, there are significant differences in the brands. Some brands (Coleman, Optimus, Primus, etc.) use regular butane. Regular butane isn't a particularly good fuel in cold weather. Other brands (MSR, Snow Peak, Jetboil, Brunton, etc.) use isobutane which is a much better cold weather fuel.

On my blog, I've got tips and tricks for cold weather canister gas use, and I've got a more detailed analysis of the various brands of gas. I've also got some information about inverted canister stoves which work far better than the typical top mounted upright canister stove. If you're interested, have a look at Canisters, Cold, and Altitude: Gas in a Nutshell.

The mechanics of how much gas in you canister is a bit more complex than just burning off the propane and leaving butane behind although something like that happens. The propane and the butane actually mix, and the mixture has a boiling point between the boiling points of its constituent fuels. The presence of the propane will facilitate the burning off of a great deal of the butane (and even more if you've got isobutane). If you're interested, I discuss what's happening on my blog in Gas in Cold Weather: The Myth of "Fractioning"

HJ

KentuckyTodd - I think you r right. Although I melted 4 pots of snow for warm drinking water before I shut it off in disgust and disassembled it.

Pumping it hundreds of times and thinking the 'vapor lock' would eventually be relieved, which it was not, was very strange.

Pumping seemed(felt) to build up pressure but it leaked off somewhere very quickly. Weird.

Never had this happen before in 20 yrs of using this type of stove in the cold.

Come on, Alan, that just isn't how the chemistry works. You're confusing things by continuing to perpetuate this myth.

In those propane/butane canisters the majority of what comes out is butane, regardless of the temperature.

Richard, have you tried a new canister?
Alternatively, have you tried your old canisters with another stove?

Ep, I hate to disagree but...

If what you observed were true (that the mix puts out mostly butane and not propane at low temperatures), then the distillation process to purify/concentrate chemicals wouldn't work.

Consider how you make brandy or whiskey...take either wine (about 12% alcohol) or a grain malt (similar or less alcohol) and boil it. It's a mixture of ethanol and water. The ethanol has a significantly lower boiling point (78C/172F) than the water (100C/212F) and what you get out the condenser part of the still is mostly ethanol, not mostly water. Indeed, to make the final stuff drinkable, you have to cut it with water back to the concentration (proof) you want. Not that you get pure ethanol...some of the other organics come out as well, or all booze would taste the same, but distillation increases the ethanol concentration specifically because more of it boils out of the solution than the accompanying water.

Same thing for a liquified organic gas mix like propane/butane. At temperatures below the boiling point of the less volatile component, you're going to get mostly the more-volatile component out of the mix. Now, I will agree that at temperatures at/above the boiling point of the less-volatile component, you'll get a mix, but that's not the point of why propane/butane mixes perform poorly at lower temperatures than the butane boils.

Oh, and before someone squawks about the temperatures quoted above, yes, those are at sea level. In a pressurized canister, both will be higher but the relationship will track.

Thanks for the feedback everybody. I'm looking forward to looking at HJ's website.

EP, these used cannisters worked on other stoves. Not recently tough.

I've been too busy to contact the vendor about an exchange, but that's the route I'm heading down. It's BS that this thing isn't working properly at 2600' inside. Not worth the frustration of heading outdoors with it.

Okay, Richard, if you're certain it's the stove. That's what I was guessing in the first place. Too bad you got a lemon!

Alan, that's fine with me. In return I hope you don't mind my demonstrating that your understanding of this is faulty.



That simply isn't true. In order for distillation to work there only has to be a difference in the proportions in the vapor versus the liquid. As long as there is enhancement of the ratio, even if the output is far less than 50%, one can distill.



Whisky is distilled from liquid at about 5% ethanol. This will boil at around 97°C, BELOW the boiling point of water, and yet the vapor, while enriched in ethanol, will contain mostly (65%) water.



At -7°C, a 15% propane mixture (by weight) results in 67% isobutane in the vapor. A 27% propane mixture has 49% isobutane in the vapor. That's at -7°C (19°F).

The fact is that you lose propane no matter what the temperature. When it's colder you lose it faster but only marginally so. It's not something you'd notice without measuring it carefully.

Alan,

Say you had two canisters, each containing 100g of gas. Canister one contains 100% butane. Canister two contains a 70/30 butane/propane mix. Assume the canister temperature is 30F and that that temperature will not vary. Assume that the air pressure is 1013 mBar (sea level). Put two identical canister stoves on each of our two canisters, open the valves 100%, and ignite. How much fuel is left at the end of our burn?

For canister one, the amount of fuel left will be about 100g. Maybe you could burn off 1g, but it's unlikely you could burn off even that much. Why? We're simply below the temperature where butane vaporizes.

For canister two, the amount of fuel left will be something on the order of 25g (that's a very ballpark figure). Why? How on earth can we burn some 45g of butane when we've been below the vaporization (boiling) point the whole time? The answer lies in the fact that hydrocarbons like butane and propane when comingled form a mixture. That mixture has a boiling point between the boiling points of the constituent fuels. Yes, propane will come out of the mixture at a faster rate than the butane, but a lot of butane will vaporize as well because it is a part of the mixture. So long as there is any propane left in the canister, at least some butane will vaporize.

The addition of propane to butane forms a mixture with a in effect new boiling point. This is the whole reason why canister manufacturers add propane. The propane allows much of the butane to be burned, butane that wouldn't have even burned a gram's worth had it been in the canister alone. Yes of course, the colder you go, the less butane will burn, but the addition of propane allows one to burn butane below the boiling point of butane.

HJ

Jim, that's a nicer way of putting it.

However...



That's not strictly true, although I get what you're saying. Butane does vaporize at 30°F. At that temperature it has a pressure of 990 mbar. The notion that liquid doesn't vaporize below its boiling point mystifies me. Hasn't anyone ever looked at their steaming pot of water as it heats up? How do you suppose evaporation works?

Of course, as you point out, to drive a stove you do need a positive pressure. Actually you need a couple of hundred millibars above ambient to push the gas through the works. And that's the key thing that the propane helps provide.

Ah, yes. You are correct of course. I'm over-simplifying, aren't I? Leave a pan of water out on a day where the ambient temperature is well below the boiling point of water, and the water will soon enough be gone.

For the practical purposes of running a stove, one needs the fuel to be about 10F above the vaporization point. Butane boils at 31F at sea level, so for a stove running on 100% butane, the fuel needs to be at about 41F or higher in order for the stove to have decent power. But you are absolutely correct, some vaporization happens well below the boiling point.

HJ

So, by the numbers that you give, a canister with 15% propane/85% isobutane will have a vapor that is 33% propane/67% isobutane. This confirms what was said - the vapor will be enriched in the component with the higher vapor pressure. This follows the basic gas laws. And as you burn that canister, the fact that the vapor will have a higher percentage of the propane than the source canister will eventually lead to almost complete depletion of the propane long before the isobutane is all consumed. The total pressure in the canister will drop as this happens, since the total pressure is the sum of the partial pressures of the components.

Well that depends on what you mean by "almost complete" and on the specific mix of gases. I don't know what basic gas laws you're referring to but if you actually do the calculation you'll find that the propane (and hence the pressure) diminishes gradually throughout the cycle. There will always be some even at the end but by then it is a small fraction.

Here's an picture of this from the MSR website:

Post! Things you learn...

Now for a practical application of how your personal stove will operate.
I use a wisperlight and superfly (depending on trip) and have always disconnected and stashed fuel in a sock, boot just to keep it warmer than it would be than if I just left it connected to the stove (nights >30).

I was taught (which has applications on Whitney) when you start at a low elevation (portal) and it's 80 degrees, buy the time you cook dinner and sack out temp is down to 25 at trail camp, the left over warmth from the fuel canister could cause ice crystals to form around the connection between fuel and stove, which would cause issues when used the next morning.

Leave stove connected to fuel, or disconnect?

Basically, yes. I'm not sure about "long before," but the propane does diminish over time and so does your total vapor pressure. Toward the very end of the life of the canister, you won't have a lot of propane left.

The fact that your best cold wx fuel (propane) burns off at a faster rate is why I typically advise people to get a brand of gas that does not contain butane. Isobutane gives one a 20F degree cold weather advantage over butane, all else being equal.

A 70/30 butane/propane mix has about the same vapor pressure as an 80/20 isobutane/propane mix at the start of a canister at say 20F/-7C, but as the propane burns off, toward the end of the canister, the 80/20 canister will have a much higher vapor pressure.

HJ

You've got two different classes of stove with a Whisperlite and a Superfly.

I usually disconnect both types, but that's more for safety than anything else. I don't like leaving white gas stoves pressurized for any length of time.

You could get condensation in the connection of a canister stove which could freeze if the stove were left connected overnight. I'm not sure how big a risk that is. I usually take the canister in my sleeping bag with me if it's going to be below freezing overnight, and yes I do disconnect the stove first.

HJ

Wow! I'm sticking to my zip stove!

Does anyone know if I will be able to buy a jetboil fuel canister in Lone Pine? If not, will an MSR fuel canister work with my jetboil stove?

Thanks, heading out to try Whitney for the first time on the 27th and I just want to be prepared.

Nah! It's not that bad. Here: short and sweet (and simple): Cold Weather Tips for Gas Stoves.

Not that there's anything wrong with a Zip stove.

HJ