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