Flame is obviously hot. However, very few pay attention to how hot it is and its degree of purity. Flame is a necessity. Ever since our ancestors discovered cooking their foods. Making bonfire when the great sun is in hiding and the night is freezing cold. Fueling generators to produce electricity. Can you imagine the status of convenience food items without it. Would there be steel, plastic and paper?
Burning wood has typical color white, yellow and red. White being closest to wood and hottest. Next is yellow and then red. Red is the coldest. Though deemed cold, it will scorch and burn any combustible object it touches. This explain why red is associated with hot perception. At the red tip is black soot. There is no burning there. Waste product basically, carbon dioxide. Other leftover are ash and sometime charcoal.
On rare occasions, I am seeing blue flame on madre de cacao hardwood. Not sure how is it? Maybe due to high concentration of resin. Short lived blue flame on wood usually have whizzing sound.
Alcohol flame is part blue and part colorless. Yellow and red parts are often imparted by wick. Impurities and water contribute to yellow part. The laboratory grade alcohol were using in Bunsen burner were almost always blue. Consumer grade 40% rubbing alcohol burns poorly. The 70% burns better but has great deal of yellow part.
Candle flame bottom part is blue and the rest follow the same pattern as wood. So wax burns better than wood? Not sure. I think I need to read more about this matter.
LPG (liquefied petroleum gas) exhibits blue flame with yellowing on top. There are slight differences from stove to stove. There are brands that can produce all blue flame. I thought it did not matter until I stumbled to a post on “coffee roasters forum”. Someone was badly obsessed with getting his roaster flame all blue. They say blue means more complete burning and is generally hotter. More efficient way to use precious gas. There are ways to tweak the setting to make it all blue.
Blue flame is clean and pretty hot at 1500 C. Impurities produce by other colors could have undesirable effect.
When we first fired up our DIY gas burner, all I wanted to see was burning rod. I was happy to see it was working well. Even happier that we can tweak the control to make the flame almost all blue. Now, I want to learn the engineering and science behind it. How can we make near perfect burner for every application in hand.
Marvin is the lead chocolate maker of Ben and Lyn Chocolate Inc. Has strong background in food research and development. Occasionally conducts training and lectures. Lecturer of Cocoa Foundation of the Philippines. Do coaching and consultancy services on his free time.