Source: Reddit does have some good info if you can wade through the piles of shit...... Odd_nonposter • 7y ago Chem Eng Much of the yellow/orange/red color of a flame is caused by hot carbon soot formed by incomplete combustion. In a flame, it acts as a blackbody radiator and emits light corresponding to its temperature. Gasoline, wood, paper, and most plastics are very carbon-rich and burn incompletely in a typical un-mixed flame. Methanol is comparatively rich in oxygen and hydrogen, and forms far less soot. A methanol flame emits far less light because of this, and bright daylight can easily wash it out, rendering it "invisible" to the human eye. Upvote 120 Downvote Reply reply Award Share Share u/EvanDaniel avatar EvanDaniel • 7y ago In addition: lack of exising C-C bonds helps reduce soot formation. As does the fact that it readily vaporizes before undergoing any reactions. Compare to oxygen-rich things like sugars that burn with lots of decomposition and soot.