How to Keep Fuel Warm During Canister Stove Operation

[Gary Dunckel]

Companion forum thread to: How to Keep Fuel Warm During Canister Stove Operation

Various techniques for keeping fuel warm during canister stove operation are described, in order to optimize fuel vaporization.

[David Thomas]

“is the BIC lighter under the stove for 5 seconds method. . . . a mostly empty canister a couple days ago and the stove slowed way down, so I briefly took pot off and heated with BIC.”

A variant on that is to leave the stove going with the pot on top and simply direct the Bic at the lower edge of the canister for several seconds until you get a roaring stove flame again and then several seconds longer.

In lieu of the disposable hand warmer, I’m going to suggest a neolithic alternative: a rock.  Put a 2-3″ flat rock in your pocket to let it warm a bit.  Put it over the stove flame or your Bic for a few seconds and then tuck it under the canister in that concave volume.  Not as convenient as a Moulder Strip or an IR reflector, but another option in a pinch.  It worked for my Cro-mognan ancestors to keep their canister stoves going and it will still work today.

[Roger Caffin]

I haven’t found that I need any canister warming technique at +30*F at 8-10,000′ here in Colorado. I use MSR 4 oz. canisters.
Very likely. The MSR canisters are iso-butane with a boiling point of about -14 C. 30 F or -1 C should be fine.

Cheers

[Jerry Adams]

I was using stove on table, it slowed down because of cold

after boiling some water for coffee, I poured the remainder on the sides of the canister and it pooled up against the canister bottom.

then I boiled another pint and it didn’t slow down

[Gary Dunckel]

Jerrry, what was the ambient temperature, and which brand of fuel were you using? Was there butane in that mix?

[Jerry Adams]

cheap butane (50% isobutane, 50% n-butane) 20 F boiling point, maybe 2 ounces left in canister

it was 29 F air temp

 

[Gary Dunckel]

That sounds like pure n-butane to me, with minimal iso-butane. If you used those Korean horizontal 8 oz. canisters to refill your Lindal valve canister, that’s likely what it was. I haven’t seen any of those that contained iso-butane, just pretty much pure(ish) n-butane.

[Roger Caffin]

Can’t be pure n-butane with a BP of 20 F.
(Pure n-butane boils at 32 F.)

Cheers

[Gary Dunckel]

You boys have me confused here. Jerry, you said the stove crapped out in +29F ambient temperatures, which is about what I would expect of pure n-butane. Then you mention that the fuel has a BP of 20F, which should have worked. I am a bit skeptical that this fuel actually does have a BP of +20F, considering how it actually performed. How can you be certain that the fuel is 50% isobutane?

This isn’t a big deal to me, since I refuse to use canisters that contain more than a tiny bit of butane. But something here doesn’t quite make sense.

[David Thomas]

Canister stoves crap out (barring use of a Moulder Strip, warm water, IR reflector, etc) 10-ish degrees F above their boiling point.

1) you need a little back pressure to get an adequate flow through the valve and to the burner head and

2) without a heat feedback technique, ambient temps need to be somewhat above the boiling point for heat transfer into the canister to occur at a sufficient rate.  Ballpark of 10F above the boiling point to run for very long.

Those horrid Bluet n-butane canisters with a boiling point of 32F would crap out around 45F ambient with extended use and since we didn’t boil & let soak back then, it was always extended use.

Edited to add: by “crap out”, I don’t mean it stops, I mean diminished flame level.  If you’re a few degrees above the boiling point, you’ll get a tiny flame.  If ambient is 5-10F above the boiling point, you’ll get a decent flame at first until evaporative cooling has reduced canister’s temperature and therefore pressure.  Then you’ll be left with a low flame until you add heat to the canister.

[Jerry Adams]

yeah, what Roger and David said

my fuel BP was 20 F – when it was below 20 F nothing came out, just above 20 F a tiny bit of flow but not enough to operate – so it must have been about 50% n butane and 50% isobutane

in part 1 I show how you need to be 3 degree F over BP to provide enough pressure to operate the stove at a slow rate which is what I experienced

and then you have to add an amount for evaporative cooling – my canister had about 3 ounces of fuel left so there would have been about 8 degree F of evaporative cooling

20 + 3 + 8 = 31 F is the minimum air temp where it would operate slowly

I measured 29 F air temp which is pretty close to the theoretical 31 F

 

[James Marco]

Exactly my thought, David. Normal readings only occur at STP, that is a standard temperature and pressure. Jets always restrict flow while increasing speed. So, a regular 0C temprature for boiling inside a closed vesel (canister,) will not deliver enough pressure to drive a flame or only weakly. I seem to have noticed a drop off in performance at around 40F or ~4.5C. with an isobutane cartridge some years ago. This might be because I almost always set it to low anyway. Conversely, temps of around 35C (~100F) will yield very high performance…but is getting off topic…

[Robert Langer]

Just some short question regarding the copper strip option:

1. How do you carry it? I am assuming that you do not bend it back and forth to a more convenient shape each time, right?
2. If it stays in the “canister shape” how do you achieve this shape in the first place? Can a strip of copper of this thickness be easily adjusted to the desired shape? (Sorry, I don’t have any experience with copper.)
3. Do you have any ideas how to make it work better with bigger canisters? Would two of them help or would that be too risky? (overheating)

TThanks for the answers in advance and thanks for the great article!

[Roger Caffin]

My 2c – but wait for Gary
1. In the pot with the stove maybe? Wherever is convenient. Don’t keep bending it.
2. With a hammer! Panel beating over an empty canister.
3. Bigger? Do you mean a 450 g canister? Hum … more difficult.

Cheers

[Robert Langer]

Thanks Rodger!

3. Not necessarily 450 g, but 220g would also be nice. As far as I understood Gary mentioned in the article that the copper strip works best with 110g canisters. He assumes that the larger surface of the bigger canister negatively affects the efficiency of the strip. Sounds logical to me. However, I was just wondering if you could simply use two strips for a 220g canister or if this would risk overheating.

Just being curious @Rodger: If you compare the “copper strip” approach and your vortex burner which approach would “win” in very cold conditions (<< -20C). Background: I am winter hiking in Scandinavia rather early in the year (February) quite often where those temperatures are not uncommon. If you do not have practical experience with those temperatures, theoretical considerations are also very welcome!

[Roger Caffin]

Hi Robert

It’s Roger, not Rodger. I have no idea where the ‘d’ comes from, although it is a common mistake. No matter.

The 220 g canister is not much higher than the 110 g one, so I would expect that a copper strip would work as well on it. The 450 g canister is much higher, so getting heat to the bottom would be more difficult. A lot of heat could be lost to the wall above the level of the fuel. Note that I am saying ‘more difficult’, not impossible.

which approach would “win” in very cold conditions (<< -20C).
Well, first of all, I am obviously biased! But there are reasons for my bias.
The standard butane/propane mix stops boiling at sea level around -24 C. If you can get the canister above this temperature a remote inverted canister stove WILL work, and it will NOT get colder by evaporation. It is highly likely that a canister in your pack or kept under your quilt will be warm enough. There is some security there.

The copper strip approach might work, but in my view it is a bit of a gamble. If you have some liquid water available before you start then obviously you should be able to get it to work in most cases. I would add that liquid water would make an inverted canister stove work very well, and so would a bit of radiation feedback from the flame to the canister.

In my experience, living and working below -20 C is a matter of keeping your fingers warm enough. That means keeping them DRY and out of the wind. Um – and not touchng any cold metal with your skin!!!

Cheers

[Robert Langer]

Hi Roger,

I am very sorry about the misspelling! Thank you for your detailed answer! Very informative!

Cheers!

[Roger Caffin]

Eh, no worries.

My memory is that it was a bit crunchy cold up here. Taschi Lapcha pass, 5,750 m Nepal. Bit puffed too :)

Cheers

[Bob Moulder]

Robert, here is a very extensive test of the copper strip method — my particular variation and some others — at -26°C, conducted by David Thomas.

I have personally used my method quite a few times in the -10 to -15°C range with 220g canisters with no problems using strip PLUS canister cozy. Commercial blends with isobutane and propane are best for very cold temperatures because they help get the thermal feedback loop going more quickly, but even straight n-butane can be used if some canister pre-warming tricks are used. I suspect — but have not tested this! — that 450g commercial blends would be fine with the strip and a good canister cozy, although I also suspect that straight n-butane might struggle in this scenario.

The photo below depicts my JetBoil MiniMo in operation at -15.5°C (4°F) as it was used for snow melting operations with a 220g canister. No problem, the stove will run strongly until the last remnant of fuel is exhausted, as if operating at +20°C…

This photo shows a 220g canister with a small amount of Primus “Summer” blend. I wanted to use up the rest of the fuel but mistakenly brought the wrong copper strip (too short) and the wrong canister cozy. So I had to do a bit of a hack and run it without a cozy. The temperature was about -10.5°C (13°F) and the stove worked well even without the ideal sized strip and cozy. I did a “Trickle Prime” by opening the valve, inverting the stove and letting some raw fuel into the burner, which when lit was enough by itself to get the thermal feedback loop going. No other warming method was used.

[Gary Dunckel]

Hi Robert. Yes, Bob and I have both found that our “Moulder Strips” do work better with the smaller 110 gm canisters than with the 220 gm ones. However, a cozy pretty much solves the problem. I haven’t tried this technique with the huge 450 gm canisters, but I tend to agree with Roger in that it might be difficult to get heat to the base of the canister (where the fuel would be once you deplete most of it).

As for the copper strip itself, I form mine so as to contact as much of the canister as I can. I do this at home, using an empty canister to pound the copper into proper shape. Bob doesn’t bother with this precision, and he is likely right that it isn’t really necessary to have maximum copper-to-canister contact. Having good contact along the vertical side of the canister is sufficient, as that’s where the liquid fuel is. Having the copper contact the top of the canister doesn’t much matter, but I like to do it anyway, out of anal principle.

For storage/transport, I leave the cozy on the canister and I keep the copper strip and foam base in a Ziploc bag. The Ziploc is put in the pack in a place where the copper strip won’t be squashed or bent. If for some reason it does get a bit deformed, it is quite easy to bend it back to proper shape. I think the key to the strip is to contour it where it touches the vertical canister wall to allow maximum contact.

You can see in Bob’s photo above that this isn’t really rocket science. All one needs to do is to somehow heat the canister with the copper strip. He was able to get that to work at -10.5* C, right? I expect that at -20* C he would have kicked himself for not bringing the right cozy and copper strip. But nothing that Bob does surprises me–he is the master of this technique.

Roger and I are both biased – he makes remote canister stoves, and I am totally sold on the “Moulder Strip” concept. The main thing about remote canister stoves is that they are heavier than most stoves. The big advantage is that you can fully enclose the stove with a windscreen, which helps with efficiency. As I mentioned in the article, I have trouble with mine at temperatures below -15* C (~ +5* F). Having a way to warm the canister a bit would help raise the canister’s internal vapor pressure to push the liquid fuel through the line to the burner head. Positioning the canister close to the hot windscreen might solve things, but sometimes it is hard to get it that close without moving the stove around. If I were to take a remote canister stove, I would also take some hand warmers and one of those cookie cup lids to secure them onto the bottom of the canister. I know that would work.

[David Thomas]

Robert:

1. classic Moulder Strips (a strip of copper) are easy to pack and reform to the canister curvature.  Other, more delicate configurations can be stored around your canisters, especially if you store your canister inside your pot.
2. I beat some stiffer materials (e.g. aluminum from an aluminum ruler) into that curvature around a steel pipe or a green, 1-pound, “Coleman” steel propane canister.  Or, with the hemispherical end of a ballpeen hammer with the metal supported on a piece of wood.  The wood yields and compresses a bit, forming a slight trough under the center line.  Note that there are both wood and rocks in most of the places we go backpacking.  Anything you can do with 8 big whacks, will be better with 30 little hits.
3. I’ve done testing at -21F / -29C with 220-gram canisters, and the better designs, including the classic Moulder Strip worked well.  As Roger stated, they are about the same height with a lot more surface area.  And I agree with him that a 450-gram canister would not perform as well due to the greater length of the strip, the greater surface area of the canister, and the contact area between upper steel canister and the strip: you want heat conducted down to the BOTTOM of the canister and thick copper or aluminum is FAR better at that then the thin steel of the canister.  Yes, combining two strips would work better and to colder temperatures.  Also, a taller canister cozy (I like wide, double-sided velcro tape as a combination strap and cosy) would help.  But at only -20C/4F?  That’s not pushing the limits of any of the better heat-conducting strips.

[DAN-Y/FANCEE FEEST]

Make or purchase a multi-use crotch pocket from Gossamer Gear and keep the canister in it while you walk the trails :-)

[Roger Caffin]

The main thing about remote canister stoves is that they are heavier than most stoves.
Some of the white gas stoves are heavy enough to be used for hammering tent stakes into rock. XGK – I am looking at you! However, there are UL versions at 80 g (cough).

The big advantage is that you can fully enclose the stove with a windscreen, which helps with efficiency.
I don’t do the ‘fully enclose’ bit: I only do a 3/4 wrap. The open 1/4 gives me access to the control valve which on my stoves is on the stove itself, and the gap allows radiation from the stove to warm the canister as well.

Dan – does a ‘crotch pocket’ work with a kilt, or is it too drafty?

Cheers

[DAN-Y/FANCEE FEEST]

Too drafty, especially in higher elevations but these guys might be able to do the kilts and crotch bags. They look better conditioned for it :-)

[Roger Caffin]

We had a group of those Alpenhorns outside our Refuge window in MariaAlm (Austria) one time on the Via Alpina. Half hour concert – they were practicing for the big music Festival the next day. Very beautiful.

Then they pulled their alpenhorns apart into short lengths and packed them away!

Cheers

[Author]

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