Companion forum thread to:

The Performance of Alcohol Fuels for Backpacking Stoves
Part One: Three Straight Alcohols and Alcohol Blends

Tony and Roger,

Nice work!

It is great to have the scientific method applied to this analysis. I have used and advocated blended fuels in the past, but have gravitated to plain ethanol over the last year. Looks like I made the right choice.

On a related side note, I know your experiments were confined to specific stoves, but if a stove was designed specifically to more completely combust isopropyl alcohol do you think that would be a safe way to use iso as a fuel? Or is using it just generally a bad idea?

-Mark

Edited by markhurd on 05/06/2009 00:31:26 MDT.

Hi Mark

Thanks from both of us.

Once the alcohol has vaporised and left the vicinity of the stove to become a flame, the chemistry is fixed. What the stove looked like ceases to matter. So I don't think that the stove will make any difference to how the alcohol burns in the flame. IPA is just bad stuff for burning.

Cheers

Nice work on the article. The comment about the stove having no affect on the byproducts I disagree/agree with. On the one hand, the stove can affect the fuel/air mixture, rate, temperature that a fuel burns at, all of which will affect the resultant byproducts. Similar to how the oxygen fuel mixture in a car will affect the resultant byproducts in the exhaust. My conjecture is that the sooty mess that ISO-OH leaves behind means that there is a lot of carbon that is not being burned, thus not enough oxygen in the fuel mixture (and most likely, to low of a burn temp as well).

Having said that, I do not think that it is practically possible to make a simple alcohol stove that can get enough oxygen and heat to burn ISO-OH properly. So in the end, the stove type will not make a difference.

I just wanted to say, great article! I enjoyed the read and really appreciate the scientific approach taken in many BPL articles.

Excellent article and the kind that keeps me coming back to BPL. This is data you just can't get anywhere else. Will there be a follow up comparing the different types of solid fules "Esbit style" coming?

IPA might not be a good choice in your garage or tent but using it in the backcountry where there's nearly always a breeze to blow away any byproducts might make it worth a consideration. Did it otherwise burn well?

A very interesting article, Roger and Tony. Thanks. For UK readers and anyone visiting the UK with an alcohol stove the methylated spirits sold here (the standard fuel for alcohol - so standard that the stoves are known as meths stoves)is a mixture of methanol and ethanol. What the percentage of each is I don't know however - it's not listed on the three different brands I have at present.

The methylated spirits sold for backpacking stoves in the UK is called mineralised methylated spirits and this is defined by Customs and Excise thus:

"in the case of mineralised methylated spirits, with every 90 parts by volume of spirits there shall be mixed 9.5 parts by volume of wood naphtha and 0.5 parts by volume of crude pyridine, and to the resulting mixture there shall be added mineral naphtha (petroleum oil) in the proportion 7.5 litres to every 2,000 litres of the mixture and synthetic organic dyestuff (methyl violet) in the proportion 3.0 grammes to every 2,000 litres of the mixture".

Edited by Christownsend on 05/06/2009 11:14:13 MDT.

>Once the alcohol has vaporised and left the vicinity of the stove to become a flame, the chemistry is fixed<

Thanks Roger, but I see merit to David R's argument that the air fuel mixture and heat of the vaporized fuel would make a difference in how completely the fuel burns: partial verses complete combustion. However, I also agree with David that the difficulties of making such a stove may make it a moot point. Of course that hasn't stopped people like Tinny from trying. See URL below. (He later took this stove off the market.)

-Mark

http://www.minibulldesign.com/myadventure/index.php?query=isopropyl&amount=0&blogid=1

Edited by markhurd on 05/06/2009 11:48:33 MDT.

Chris,

The additive 'Wood Naptha' is another term for methyl alcohol, which suggests that the 90% is ethanol.

A quick google search on [ "mineralised methylated spirits" msds ]showed most products in England to be 90%-95% ethanol.

MSDS - Materials Safety Data Sheet

If you search from there and include a manufacturer name I think you'll find the details.

Thanks Greg. I didn't know to search for MSDS. Searches suggest the composition is 60-90% ethanol and 5-10% methanol.

The UK products are generally 90% ethanol, then methanol and the minor additives as listed above.

The MSDS can be a bit vague - they typically say something like 60-90% ethanol.

Edited by nsjohnstone on 05/06/2009 12:36:26 MDT.

Chris and Neil,
On the MSDS look for the section on the additives. It will usually give the parts in percents, the remainder of the product then being ethanol.

Tony and Roger

Excellent work! As was mentioned above, this type of analysis, along with the sheer creativity of BPL’ers, is what keeps me coming back. It is nice to see some numbers behind the rhetoric.
I wonder if you would consider the following for your future work. Since your independent variables (X-axes) are categorical instead of continuous, please use bar graphs instead of line graphs. Will you show the standard deviation for you data, or otherwise indicate significant or non-significant differences? I realize that this would increase the sample sizes. How tight are your means?

First of all, I commend the authors. Like the others, it is articles like this that make BPL the "Science Magazine of Backpacking".

Is there any chance in future statistical chart presentation if a sidebar arrow can be displayed with the wording "Better" showing which way is better, versus which way is worse.

I had to read considerable text before figuring out which direction in the charts was more desirable, but with the arrow icon, one would immediately know.

Would the Americans reading the article come to the conclusion that Yellow Heet is the best to use outside of EverClear in the USA for stoves?

Edited by marti124 on 05/06/2009 15:16:38 MDT.

Roleigh,
This american favors Sunnyside Denatured Alcohol. It's readily available in gallon cans for about $13, and is around 94% ethanol.

The MSDS for sunnyside denatured alcohol is here:

http://www.sunnysidecorp.com/pdf/msds834.pdf

I've pretty much got my system down so I never come in skin contact with the stuff, and of course ventilation is a priority. Then again, the name is not quite as creative as those brands of everclear...

James

> IPA might not be a good choice in your garage or tent but using it in the backcountry
>where there's nearly always a breeze to blow away any byproducts might make it worth
> a consideration. Did it otherwise burn well?

Nope! Sooty.

Cheers

Hi Chris

"in the case of mineralised methylated spirits, with every 90 parts by volume of spirits there shall be mixed 9.5 parts by volume of wood naphtha and 0.5 parts by volume of crude pyridine, and to the resulting mixture there shall be added mineral naphtha (petroleum oil) in the proportion 7.5 litres to every 2,000 litres of the mixture and synthetic organic dyestuff (methyl violet) in the proportion 3.0 grammes to every 2,000 litres of the mixture".

Yes, well, you would NOT want to drink that stuff!

Cheers

Hi Roger,

Destitute alcoholics do drink it though! Back in the 70s when a Trangia was my only stove you had to sign the poisons register to buy meths in Scotland and shops would only sell 500ml at one time because of the problem with people drinking it. I can remember going to several shops and buying a bottle in each on one long walk! I used to take the Trangia with me so I could show it them if they queried my purchase. Now I can buy 5 gallons no questions asked, no signature required.

The purple dye makes it very distinctive, as does the smell. You'd really have to be desperate to drink it.

Cheers,

Chris

Hi James

> Since your independent variables (X-axes) are categorical instead of continuous, please
> use bar graphs instead of line graphs

Understood. I will look at this for the future.

Standard deviations - nice idea, but for many of the readings we are taking only 3 measurements. Provided they are consistent (within maybe 5%) we run with the average of those 3. Quoting a SD doesn't seem justified.

Cheers