Coleman Xtreme Canister – claims usable to -27C/-16F

I make zero attempts to be politically correct. I totally reject the concept.  :)
On the other hand, I will go to considerable lengths to be scientifically correct. That is my life.
Technically (ie legally) I cannot speak for Backpacking Light: only Ryan Jordan can do that. But I do try to avoid getting BPL into strife. That seems fair to me.

Could the canister slosh if there was 140 g of n-butane in it? The question does not obtain imho as I don’t think you could get more than about 132 g of n-butane in the canister. There just ain’t room.

More to the point though, if you can HEAR sloshing, that means the surface of the liquid is slapping against the inside of the canister. To me, that means there MUST be vapour space inside.

Cheers

Gary, based upon your measurements and Roger’s math, that question is very close to being answered. :^)

For practical purposes we have the touch test for temperature and now the slosh test for volume.

Getting back OT,  I am looking forward to actual field tests of this canister in very cold temperatures. However, even if the propane content is 40% or perhaps a little higher, all they’ve done is bought a little more burn time and the performance will diminish just like the others when the laws of physics catch up with it. Now, if they’ve figured out a way to somehow keep the propane/isobutane mixture evenly distributed during the burn — which seems very unlikely — THAT would be something.

if they’ve figured out a way to somehow keep the propane/isobutane mixture evenly distributed during the burn — which seems very unlikely — THAT would be something.

The mixture is a true solution, like a salt solution.
If you use the canister upright the propane will tend to boil off faster, just as with any other canister. No difference at all.
If you use a liquid feed it will stay perfectly mixed. It will not separate. The laws of chemistry (and physics) will still apply.

Cheers

In an upright stove, and the canister is cold for example at the boiling point of n-butane, then the propane must boil off faster?  Leaving the remaining fuel in the canister a higher proportion of n-butane?

As opposed to, if you use the upright canister much higher than the boiling point of n-butane, then the remaining fuel in the canister must maintain the original proportion of n-butane and propane?

The propane will boil off preferentially. The higher the ambient temperature, the less the significance of this. At +20 C, irrelevant.

Cheers

@rcaffin, If a liquid feed eliminates the issue of the different boiling points, then what is the advantage of having a higher propane ratio – i.e. if it still must be used inverted?

Wouldn’t it make sense to just use straight butane, with a thinner walled canister?

Hi Edward

A good question, but with a good answer.
To get liquid out of the canister, something inside has to push it out. And push with enough force (or pressure) that there is a fast jet of gas in the burner to entrain air for burning, otherwise you end up with a smoky candle.

Butane stops boiling off vapour at 0 C. So at -2 C you will get NO vapour out of a straight n-butane canister. Just, nothing. Plenty of us have had that problem in the past. A propane/butane blend however will still be boiling off vapour a bit below -20 C.

Cheers

Gary, IIRC the most N-butane I’ve put in was 123g. (If some of our resident experts think that’s insane, please advise!) – B. Moulder

I just saw this post.  I think 123g of N-butane is unsafe!

The reason you need the volume in the canister is to allow the liquid N-butane to expand as the temperature rises.  Gas is compressible, liquid is not.  All you need to do is calculate the density of N-Butane at the hottest you might expect it to be and multiply it by the volume of the canister (reported by Gary to be 220 cc).

I think a good design temperature would be 50 C (122 F).  At that temperature you can only fit 119 g of fuel.  At 123 g, the canister would fail at 98 F.  That is a pretty warm day, but certainly not an unreasonable temperature for a canister to reach.

Hmmm

Is Roger wrong on the science? Is the ‘slosh test’ fatally flawed?

Is Roger wrong on the science? Is the ‘slosh test’ fatally flawed?

The slosh test is fine for that temperature, but the vapor volume can disappear as the tank gets warmer.  Roger’s explanation is fine he just didn’t consider what happens things heat up.

In the interests of getting this right—and not going simply by my “IIRC 123g” statement—I just refilled one of the Primus canisters for which I have an accurate empty weight, which is 101.9g (with the plastic cap). The filled weight (with cap) is 217.3g, and there is still plenty of ‘slosh’ volume.

So the accurate weight for the N-butane (still somewhat ‘ballpark’) is 115.4g. Could’ve squeezed in a few more grams but that’s close enough, and you can hear the resistance to fuel flow as the donor/recipient canister pressures start to equalize.

EDIT TO ADD: The best, safest practice is to refill with no more fuel than whatever is listed by the manufacturer on the canister, usually 100g or 110g. That’s what I’d recommend to anyone else. Get yourself a good gram scale and use it!

you can use the scale to weigh your stuff and reduce pack weight

and measure down to put in each baffle : )

I also use it for mixing epoxy.

But I suspect the densities of Part A and B might be different, and therefore it should be measured by volume and not weight.

Damn, there’s always a catch! ;^)

No, the slosh test is not ‘fatally flawed’: if the canister sloshes, there is obviously vapour space.
However, I did not go into the whole question of variations in temperature and the coefficient of expansion. If it stops sloshing as it warms up – DANGER!

Yes, you could add another few grams or 1-2% of total, but then you might be going from the ‘quite safe’ to the ‘risky’. Is another 1% of fuel worth the risk?

I agree totally with Bob: go with what the mfr lists, and weigh accurately.

Cheers

Then they can use a gas mix with a higher vapour pressure and still pass DoT regs.

@rcaffin – I doubt that they’ll be concerned with the US DOT.  They just don’t let us have those kind of pressures for some reason in the US.  Powermax was as I recall a 60/40 blend in the UK (I saw it printed on the side of the canister), but it was only 65/35 here.

I’ve heard of 70/30 isobutane/propane blends available elsewhere, but for years the best we’ve ever had was MSR 80/20 — although Olicamp now says its blend is 75/25 which if consistently accurate would be a pretty good blend.  Somehow I trust MSR more.  Olicamp isn’t a manufacturer with technical expertise.  They just re-badge things from overseas.  But let us hope for the best.

HJ

the canister is same distinctive shape as the CV 300 canister but with a screw thread valve instead

@scunnered – We’ve never had CV300’s in the US.  All we’ve ever had were CV270 and CV470 (and we don’t even have those anymore, alas).  I have long been curious as to exactly why a CV300 exists.  What is its capacity?

HJ

I doubt that they’ll be concerned with the US DOT.  
I am not too sure who ‘they’ is, but if you want to sell goods in the USA, DoT regs are The Law (in the USA).
To be sure, the regs may be slightly different in other countries. We can get 70/30 mix with iso-butane here in Oz, but I don’t think you can in USA.
For that matter, a Swedish company sells 100% propane in ‘hair spray’ canisters – in Europe. I can’t get them in Oz.

Cheers

if you want to sell goods in the USA, DoT regs are The Law (in the USA).

Well, yes, but that’s my point.  I don’t think they’re ever going to sell Coleman Xtreme gas in the United States.  From what I’m reading (see link) it’s a 60/40 blend of n-butane and propane.  I don’t think that’s going to pass muster here.  We never got to see the 60/40 Powermax canisters that the rest of the world got to use either.  We were limited to 65/35.  I don’t think we’ll see this 60/40 mix either.

https://www.norwichcamping.co.uk/shop/product/coleman-c300-xtreme-gas-4824/

That said, maybe we’ll get a version that is 65/35 of the Coleman Xtreme.  That would be fantastic for inverted canister stoves.

HJ

Just wondering ‘out loud’ here… and for use in cold/very cold environments

What would be the difference in stove performance between 60/40 and 65/35—or even 80/20, while we’re at it—since the propane in that instance (Coleman Xtreme, inverted canister operation) is essentially just a propellant? (A propellant which, quite handily, becomes the primary/only fuel source as the supply in the canister dwindles.)

As far as upright canister use goes, it seems to me the 60/40 n-butane/propane is going to fare better at first than the 80/20 isobutane/propane blend but that the 80/20 will burn better after the propane is exhausted and isobutane becomes the primary fuel source vs n-butane for the 60/40 blend.

you could refill a canister with straight propane

you’d need to find the right adapter to do it

as long as you keep the canister below some temperature, like 70 F, you’d be okay

that’s what some respected BPL people said on some other thread

I sure as heck wouldn’t do it because I’m happy with plain-jane-n-butane. But that seems REALLY unsafe.

All by itself, depending upon the system to remain 70°F or lower sounds like an invitation to disaster. Already, commercial blends can explode if left in a hot car. HJ has a photo of that somewhere, with the back window of a car blown out. As I recall, it didn’t ignite, but it would have taken only one tiny spark to do so.

Nope, not gunna do it.

neither would I, but I have a hard time finding a time when it’s too cold for cheap butane even with no assist techniques

More pressure is more better — in cold weather.

According to Roger and Stewarts charts in their excellent gas in cold weather article, 80/20 isobutane/propane has about the same pressure as 70/30 butane/propane.  Therefore, 60/40 butane/propane would have considerably higher pressure.

Yes, the propane would boil off at a faster rate than the butane — on an upright canister stove.  So, don’t do that.  Use it with an inverted canister stove where the proportion of the fuel mix stays relatively constantly (you will lose some propane while lighting it upright).

65/35 butane/propane would still be better than 80/20 isobutane/propane — for inverted use.

I’m not sure that 65/35 butane/propane would be better than Olicamp’s 75/25 isobutane/propane mix.  I’d probably stick with the Olicamp 75/25.

HJ

Jerry, you mentioned elsewhere that the lowest you’ve experienced recently is 25°F, so yeah, I wouldn’t worry about it.

Yesterday morning I fired up my straight butane-powered JB at 29°F with no problems, and with no pre-warming of the canister BTW. Yes, it was in the field as I was doing another overnight quickie-trip to test some other stuff, so coffee and oatmeal were on the line.

IME you’re not going to learn a whole lot when testing above about 20°F with any blend containing propane. The one thing I did confirm is that shaking the canister does indeed free up a few molecules when trying to start the stove just below the known vapor temp. First time I lit the JB yesterday morning the flame was very weak. Turned it off immediately and shook it, opened the valve and re-lit and the vapor flow was significantly stronger.

However, I am definitely NOT going to recommend this to anyone because it really could cause a huge flare-up if somebody should shake the canister while the stove is running and liquid fuel enters the jet.

Ben: Thanks for weighing in.  I was skimming this thread offline yesterday and getting more and more agitated that thermal expansion of the liquid wasn’t being considered.  ChemE’s unite!  Dyslexics untie!  Butanes expand at 10x the rate that water does.  Propane at 13x the rate.  (Hydrocarbons in general expand and contract with temperature more than water, and more so as you go to lighter species).

Does the “slosh test” work?  Sure, at a particular temperature.  But if you are going to get the canister to a higher temperature, you’d need to check for slosh at that temperature.  The problem lies in getting to that temperature without losing “slosh” because at a degree or two over that point, the canister ruptures.

Is this a risk during use?  Not much.  As soon as you start using the canister, you’ll be removing liquid volume and through evaporative cooling, the canister will be losing heat.  And thermal feedback from radiant heat, conduction down the valve stem or through a Moulder Strip has a bit of a time lag during which you will have burned off a few more grams of fuel.  And, with an open valve, there is a bit of pressure relief, albeit with a liquid fuel getting to the burner and a resulting fireball.

I see the greatest risk as being during transport, after refilling and before any use.  A car interior in the sun could get to 140F/60C.  If you filled canisters at 68F/20C, then you’ve increased the volume of iso-butane 0.0012 x 72F = 0.0022 x 40C = 0.087 or by 9%.  Did you fill your canister to less than 90%?  I hope so.   And propane expands a bit more over that temp range.

So are we okay if we stick with factory-filled weights?  That’s great if you stick with factory butane/propane ratios.  Then the density of the mixture remains the same and is a good proxy for volume.

If you fill with more butane than the factory did?  That’s fine – n-butane and iso-butane are both denser than propane so you’ll get to factory fill-weight before you exceed factory fill-volume (of liquid).

But if you fill with more propane than the factory did?  Watch out!  Of course a higher fraction of propane makes for a high vapor pressure – that might have been your motivation in the first place: to make a better “winter mix” and tell yourself you’d never leave it in a hot trunk.  But liquid propane has a lower density (0.508) than liquid butane (0.584 and 0.563).  So the same weight of propane takes up more volume.  And propane has a higher coefficient of thermal expansion.  So everything is working against you:

• the higher mole fraction of C3H8 makes for a high vapor pressure at each temperature
• the lower density of C3H8 puts more liquid volume into the canister for a given fill weight and
• that liquid propane will expand more with heating.Would I ever do this, myself?  I may have.  But only to 90% of factory fill weight.  And label that higher-propane canister REALLY clearly.  Store it at room temperature, no more.  Transport it in the trunk or roof rack, never in the heated passenger compartment.  And use it that same winter so you don’t have it around next summer as ambient temperatures rise and you can’t grab it by mistake for a summer trip.  Even if you’ve burned off another 10% of the volume, you’ve only solved the expansion-of-liquid problem, not the higher vapor pressure issue.  Instead of a canister that should never get “hot to the touch” on top, you’ve got a canister that should never get “warm to the touch” and that requires a lot more diligence.