My understanding is that the black residue is part of the nature of isopropyl. 99% won't make that go away.

I read on another forum of a guy experimenting with different blends of lower alcohols (Methyl, ethyl...) with the isopropyl (forgotten which percentage) and had some luck with good boil times and clean burning.


Maybe it was backpackinglight.com. Less than a year ago, I think.