Denatured alcohol is basically 100% alcohol with some poisons added so people won't drink it. It is superior to the 70% to 90% mixtures for the reason Susan mentioned..no water. If you were to burn the 70% in a pop can stove..it would smoke more, be less efficient and leave black soot on your pot...but then in a survival situation I could give a crap about some soot on my pot. Don't take our word for it though...build you a stove and then experiment with it. You may also want to check out this website..pretty good resource. Alcohol Stove basics