Mixing Alcohols

[Mark Hurd]

I've been in the kitchen all day with a bunch of mutilated beer cans, playing with fire, hot water, and thermometers. My wife thinks I may have been drinking some of the fuel, but I swear I'm sober. I've been on a quest to get 16 oz of 60 degree F water to a rolling 212 F boil on 1/2 oz of alcohol. I've used a MiniBull Micro-Sith, Gram Weenie, 2 kind of homemade penny stoves, a Cat stove, and a Caldera Cone with 1.3 Evernew. I employed a Heineken pot, Evernew 1.3, Brasslite 600, and MSR Titan pots. In addition to all the different stoves and pots I tried different heights above the stoves, I clamped aluminum fins on the pots and played with wind screens.

I know, I know… "How hard can this be?" Many of you can get a boil easily on 1/2 oz of alcohol, right. I could too if I started with 70 F water, but I decided 60 F water is closer to what I would find in the wild, so 60 degrees it is. (My very rough calculations showed that a 100% efficient stove could do it with about 8ml of ethanol so it is theoretically possible.)

With many of my test runs I was able to get the water up to 190-205 F which of course is hot enough to "cook" my freezerbag meals, but that is not the point. I wanted rolling boil, tiny bubbles roiling the water, heavy steam! But it was no go until my wife ( she's a chemist ) suggest I try mixing alcohols.

Turns out that isopropyl (91% rubbing) and methanol (Yellow Heet) mixed 50-50 burns hotter than the methanol that I was using by itself. And although there is some yellow flame toward the end of the burn, there was only minimal soot. Oh, and I got a real 212 F rolling boil with several stoves using a 1/2 oz. of this mixture.

Anyone else out there mix fuel. Any suggestions on better combos or ratios? Any and all input appreciated.

-Mark

[James D Buch]

Your wife had good insight. Actually, it is a little surprising that some engineering oriented stove maker wouldn't have already tried this and reported upon it.

If you can convert this into some measure of how much weight (grams per standard boil burn or grams per 5 or 10 burn hike) you can save by doing this bit of chemistry, then the ultralight crowd would have some basis to be more interested.

Without doing any calculations myself, you may have achieved a 10% fuel weight savings for just boiling.

When you turn this into the 60F vs 70F baseline, many people could easily fall asleep out of misunderstanding.

Jim

[Roger Caffin]

Mark
> Turns out that isopropyl (91% rubbing) and methanol (Yellow Heet) mixed 50-50 burns
Just remember that methanol is toxic to humans. Ethanol has slightly more energy content and is not, well, actually toxic. In addition, ordinary methylated spirits should not have much water at all, giving greater efficiency.

Cheers
Roger

[Mark Hurd]

Jim,

Good point.

With this mix I can "cook" 2 full meals a day( 4 cups of water) on 1 fluid oz of fuel which would weight 0.79 oz wt. or 5.5 oz wt of fuel for a 7 day trip.
That is a better way to look at this!

Roger,
Thanks, I am aware of the toxicity issue. This is true for naphtha or white gas and other chemicals we use so one should proceed with caution and care when handling these substances. Still I think if one is careful they can be used safely.

Thanks,
-Mark

[Brett .]

In order of energy density, isopropyl alcohol is highest, then ethanol, then methanol; so you can expect stove performance to be proportional. For details look up gravimetric or volumetric energy density of these fuels.

I use 100% methanol in my Caldera Cones because it is easily available from my drugstore; but I wish I could get 100% ethanol or isopropyl here in Japan. Maybe when I figure out the kanji I can choose the right fuel additive from my auto parts store.

IME, 30ml of Methanol will boil 600ml of cool water in my Caldera Cone; a little more fuel required on a cool day or at high altitude, probably because there is less O2 for the combustion process?

[Jay Well]

Mark:

I have also been trying various stoves and pot combinations to get 2 cups of water to a boil. I am very excited to try mixing fuels to see if I can get more consistent boils. I was curious what stove, pot, accessory combination allowed you to get consistent 2 cup boils with your new fuel mixture?

[Mark Hurd]

Brett,
The main problem with isopropol alcohol is that it has a higher boiling point and lower vapor pressure than ethanol or methanol and doesn't burn as readily giving off a yellow sooty flame. I think the mix with methanol helps keep the heat in the stove high and volatilizes the isopropanol so that it burns more completely. Since isopropanol has half again as much heat capacity or energy density as methanol (7.2 kcal/gm vs 4.7 kcal/gm respectively) you get a much hotter flame. On the other hand it may just be magic. #;-)

The bottom line is that I can cut my fuel wt. a lot with this mix. I can get 500ml of 15.56 degree C water to 100 C with 15ml of the 50/50 alcohol mix.

-Mark

[Mark Hurd]

Jay,
I settled on the Evernew 1.3 Ti pot due to its larger bottom. Seems the wider the pot the better the heat transfer. The beer can pots heat the worst and are the hardest to get to a boil in my experience. I was able to get consistent boils (60 F up to 212 F) with the Evernew and the SuperCat stove and a Caldera Cone setup. The Micro Sith also worked. I had trouble with flare ups with the Gram Weenie that I am still working on. Also, I tried 75/25 iso/meth mix but it was not clean burning and made a mess of my pots. Hope this is helpful.

-Mark

[Brett .]

Mark,
I'll try that combo if I can find isopropyl; probably sold as medical alcohol here too.
Thanks!

[Scott Ridgeway]

Would painting the bottom of your pot with black heat paint help?

[Michael Martin]

Hi Guys-

Wow, what a fascinating discussion!

I've long been a fellow stove tinkerer and have a few comments to throw into the mix.

1) As Roger mentioned, Ethanol has more BTU's per ounce than Methanol, and so provides better weight efficiency than Methanol. It might be interesting to see how Ethanol/Isopropanol mixtures perform.

2) Here in Idaho, we can easily get 99% Isopropanol at the supermarket!

3)I've done a number of burn tests with the 99% juice and had the same yellow flame and soot problems already mentioned. In addition to the vapor pressure/boiling point issue raised, I recall there being something about Isopro's molecule that lends itself to incomplete combustion. Further, in addition to soot production, incomplete combustion means that you don't release all the heat possible when burned. (Sorry, I'm not a chemist — maybe somebody else can comment on this in more detail.)

3) For reference, by my calculations:

Methanol = 9755 BTU/lb
Ethanol = 12764 BTU/lb
Hexamine (Esbit)= 12926 BTU/lb
Isopropanol = 14220 BTU/lb (assumes complete combustion)
White Gas = 18500 BTU/lb
Butane = 21165 BTU/lb
Propane = 21656 BTU/lb

(Yes, BPL's metric advocates can hate me now…) ;-)

Cheers,

-Mike

[Roger Caffin]

Hi Scott

> Would painting the bottom of your pot with black heat paint help?
Doubtful. It might work if you had a radiant heat source, but alcohol flames are not that bright … Conduction from the hot gas to the metal surface is the main channel.
The insulating properties of the paint might hinder the heat transfer more.

Cheers

[Franco Darioli]

It has taken me a few years to realise that what you call alcohol and we call metho are similar but not the same ( methanol and ethanol) . That finally explained why I was consistently getting different results from the ones published from over there ( the US).
A few days ago on a different forum someone from Scandinavia, possibly Norway, mentioned that over there they dilute alcohol with water to "cool it down" ( I cannot remember why….)
So I did some experiments using Isopropyl Alcohol (expensive here in Australia) , adding water to Ethanol and adding both water and Isopropyl.
I used the White Box stove because I have a couple of them (for side by side tests)
The Isopropyl/Ethanol mix (50/50) does burn hotter but burns a little quicker.
No gain for me.(negatives,more soot wider flame)
The Ethanol plus water (10 to 15%) burns "cooler" , takes longer to boil but boils for as long as straight Ethanol. Two big plusses for my set-up are:
1) it makes the WB stove about 15% more efficient
2) it narrows the flame to about half the normal spread so I don't get flames up the sides of my pot. ( curiously the flame is bluer than otherwise)
An 80% Ethanol,10% Isopropyl/10% water gives similar results as for Ethanol only , but does leave some soot.
All considered this appears to be also a 10% increase in efficiency.

Looks like mixing fuels does indeed improve the efficiency.
I propose that Roger Caffin should do for BPL a full set of tests along these lines so that we can all have a more scientific result.

No pressure Roger, but Spring is here….

Franco

[Mark Hurd]

Franco,

First- Thanks for your mixing experiment results. I was beginning to feel lonely.

Second- Wow, adding water to the fuel! What kind of upside-down thinking is that? :-)
Very interesting.

The isopropyl alcohol (cheap here in the US) that I was using was 91%. So my mix was more like 50% methanol/91 %isopropyl/9% water. Maybe I will try to water down the isopropyl ( actually it also comes stock in 70% which is even cheaper here.)

Also, I wonder if the methanol, which is more volatile than ethanol, somehow allows the isopropyl to burn more completely? My 50/50 mix left only a tiny dot of soot on the pot. Easily wiped off with your bandana or sarong (oops! that is another discussion)

Finally- I second your proposal that Roger do a BPL article.

-Mark

[Franco Darioli]

Here is a picture to prove the point. The pot on the left is a 900 ml container ,the one on the right is 1000 ml, so the one on the left is aprox 5 ml smaller in diameter. I used the tea light container to fill the stove, about 20 g.
The stove on the left has 85% Ethanol and 15% water, the other one has 100% Ethanol. ( for Roger, that 100% is 97% plus 3 of whatever they put in it…)
The mixed version took longer to prime and to come to a boil but the boil lasted a few seconds longer so it is more efficient.
I then added a bit more water, around 20% total, the flame was narrower again but it failed to bring the water to a boil.
Franco

[Joe Kuster]

From my understanding the most common reason to add water to alcohol based fuels is to allow for simmering or otherwise reducing the output.

[Yukio Yamakawa]

Brettさんへ

アルコール燃料を入れるならばパウチ容器はいかがでしょうか。一例ですが、１８０ｃｃ入りの”ウイダーinゼリー”６０ｋｇの体重で踏み付けても破裂しないほど丈夫です。しかも東京では、簡単に手に入ります。他でも、入手しやすいと思います。

http://jp.youtube.com/watch?v=WcxmuWlX9lA

この動画は、私が自作したJSBサイクロンストーブに,アルコールを注いでいる様子です。以下は機械翻訳ですので、誤記があるかもしれません。

To Brett

The alcoholic fuel is inserted, if is, will the pouch container how probably be?

It is one example, but trampling at weight” of [uida] in jelly” the 180cc entering, the extent which does not burst it is strong at 60kg weight. Furthermore in Tokyo, it enters into the hand simply. You think with in addition to that it is easy to procure.
http://jp.youtube.com/watch?v=WcxmuWlX9lA
As for this animated picture, I am the circumstances which pour alcohol to the JSB cyclone stove which the original work is done.

[Sam .]

>"Anyone else out there mix fuel. Any suggestions on better combos or ratios? Any and all input appreciated."

No advice but, FYI the red bottle of HEET (ISO-HEET) is 99% Isopropyl if I remember correctly. Brett might even be able to find that in Japan's auto parts stores.

[Donna C]

Mark-
See my post under tealight stove. Tinny has been doing this mix and has sold me on it. I use it for my tealight stove. I've used 70% rubbing alcohol with denatured, 50/50 blend.

[Bill Burk]

If you do add water, do it in the field and don't count it as fuel used :)

[Mark Hurd]

Ok, I’ve been at it again. Trying to improve the efficiecy of my Heineken cone setup, I have been mixing alcohols again.

All these tests were done in my kitchen with ambient temperature of 68 F. Altitude is 750 ft. Each test started with 500 ml (16 fluid oz) of 60 F water. Fifteen ml of alcohol was used for each test, I used an open vented chimney stove inside my Heineken cone. The Heineken can was used as the pot.

The table below shows my data:

All the fuels provided adequate hot water (500 ml) to prepare a meal on 15 ml (1/2 fluid oz). 190 F water is definitely hot enough for most uses around camp. However, as expected the Iso-Meth that I have used before and the Iso-Denat. were better at getting the water to boil. And the Iso-Denat mix was the best. This makes sense due to the higher heat capacities of these two alcohols (Iso = 7.4 kcal/gm, ethanol =6.4 kcal/gm versus methanol = 4.7 kcal/gm) (The ethanol is “denatured” with methanol so it’s heat capacity is somewhat less than 6.4 kcal/gam)

Since I got boiling water with the Iso-Denat and it continued to boil I could potentially decrease the amount of fuel used. Is six cups of hot water on an 30 ml of fuel possible?

-Mark

[Kyle Purcell]

Mark,

This is some really good stuff! I really enjoy hearing how you mixing escapades go, because it helps me tweak my experiments.

So, if I'm reading this correctly, you had the shortest burn time with the meth, and the longest with iso/denatured mix. Second was iso/meth with a boil achieved both times (iso/den and iso/meth).

My question is about the iso/den mix. It seems that this was a better mix with a longer boil time. Is this something that was consistent or did you try each mix once? I ask this because I have been meaning to try a iso/den mix for a while and my laziness has kept me from doing so.

[Kyle Purcell]

just saw your post again, and this time it was a chart (guess my browser was messing up). Looks like you tried each mix three times?

[Tony Beasley]

Hi Mark,

Thanks for the information on mixing alcohols, keep up the good work.

When I entered a similar debate a few weeks ago it was strongly pointed out to me that denatured alcohol that is available in the US varies quite considerably in what additives are added and the ratio of ethanol and these additives, and therefore was an unreliable source of fuel.

http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/10381/index.html?skip_to_post=75683#75683

"This is mostly due to lack of experience and too many charts and graphs. Denatured alcohol is just ethanol with a bunch of nasty stuff added to make it not drinkable. Ethanol is great for stoves–but—you can not purchase it without additives unless you buy 200 proof drinking spirits—good luck with that. The addatives are the problem with denatured alcohol. If you had used this denatured alcohol from different sources you will discover that sometimes it has stuff like bleach in it. I have had it give off fumes that sent me running for my life because it caused my eyes to burn as well as my lungs. I have also seen a thick brown residue left behind that caused jets to plugup as well as causing bubbles of a plastic like substance to form inside the stove. I would say from my experience and from the feedback of my customers, that denatured alcohol should not be used at all. I have read all the warnings about methanol and after years of using it to fuel stoves, I have had no problems at all with it and if used with commom sense it is the fuel of choice. I grow very tired of people telling me how bad something is without any pratical experience using it. That having been said—some people can only get denatured alcohol as a fuel because there country has placed limits on ethanol consumption. —-Tinny—Minibulldesign—Have a great day!!!"

A quick check of data sheets for US denatured alcohol showed ethanol amounts varied from 50% to 92%, this would mean a there is a variation in performance of the different mixes.

In Australia it I have only seen denatured alcohol that has 95% ethanol mix and is clean burning.

Would it be possible to post the denatured alcohol ethanol/additive mix that you are using for your tests as it is important analysing the final results.

I am currently writing up part one a two part technical report into alcohols and alcohol mixtures as a stove fuel which I hope to publish soon.

Tony

[Mark Hurd]

Tony,

I was vaguely aware of the issues with denatured alcohol here in the U.S. so I appreciate your input.

I have been using S-L-X Denatured Alcohol by Klean-Strip which is sold as lacquer thinner and marine stove fuel- if you believe the label. It turns out to be about a 50:50 mix of ethanol and methanol with a splash of Methyl isobutyl ketone. The Material Data Safety Sheet is Here. It should supply you with the info you need.

Concerning Tinny's arguments about the safety of methanol vs denatured ethanol I would have to say I like Tinny and I own several of his stoves, but methanol in not benign. The recommended PEL (Permissible Exposure Limits) for ethanol is 1000 ppm, methanol only 200 ppm, and in denatured alcohol they add a percent or two of methyl isobutyl ketone which is only 100 ppm. The lower the number the less safe (more poisonous) the substance is.

All this is to say that none of this stuff is risk free, so I try to be careful with all fuels. As to whether they put bleach and plastic into denatured alcohol here- your guess is as good as mine.

-Mark

P.S. – Sorry, didn't mean to get so preachy.

[Author]

Posts