alcohol stoves: 50/50 mixed fuel

Methanol burns cleanly and is available in neat Heet packages at walmart for about $0.16/oz.  But the BTU is relative low, around 9,000btu/pound.

Isopropyl alcohol (the 91% stuff) is about 12,000btu/pound and can be had cheap at drugstore sales, so why doesn’t everyone use it?  Because it soots like a madman.

I stumbled into some posts like this one on the various “gram weinie”* forums.  I did some googling and, sure enough, mixing methanol and 91% iso is a fairly common practice among stovie experimenters.
alcohol fuel mixing experiment

23% better BTU payload in at a 22% discount (sale price at Walgreens this AM) sounds good.  But how would it work?

It worked well.

Burn times for .5oz of 50/50 was 6:30, somewhat longer than I’ve been seeing with methanol alone (around 5:50).

Hmm, how to test for sooting.  I wrapped a pot in a layer of foil, shiny side down, and cooked over .5oz of 50/50, methanol, and iso (left to right in the pic above) in an Altoids burner sitting in a folding esbit stove.  After each run I flattened out the foil and ran an alcohol-moistened cotton ball down the middle.  The 50/50 and methanol were indistinguishable:  no visible soot on either the foil or cotton.  The iso foil and cotton were visibly blackened.

There was a bit of orange (5-10%) in the Altoid cooker’s flames.  Oddly, my orange-burning civvie Trangia seemed to burn bluer with 50/50 than methanol.  Hmmm.

When I ran 50/50 with a bit more headspace between the burner and pot (civvie Trangia under an inverted Westwind triangle stand) there was light sooting which wiped off easily.

Conclusion:  50/50 may be best for setups that have very little headspace, where long, orange flames do not form.  Like a side-jetted penny stove where the pot sits on the stove itself.   A test with 2/3 methanol and 1/3 iso may be in order.

fratermus

* ie, ultralight hikers.  They count grams to keep their packs and other gear light weight.

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One response to “alcohol stoves: 50/50 mixed fuel

  1. Pingback: Daily prep: more fuel testing, Mora | mindful omnivore

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