What's In A Candle Flame?

What is a candle flame really made of? I am at the Palace of Discovery in Paris to do an experiment that beautifully demonstrates the answers.

Ok, so we're turning on an electric field here and we see that the flame is spreading out. That's very cute; it's like a butterfly. And you can see that the flame has two separate pieces to it now. One is going towards the negative plate. Those would be the positive ions, and the negative ions will be going towards a positively charged plate. So we see the flame kinda flattening out.

But if that didn't convince you that flame contains ions, then check part two of our experiment where we compare the conductivity of a flame to the conductivity of air, which is normally a pretty good insulator. It requires about 10,000 volts to break down a centimeter of air. So right now, this plate is about 20,000 V. You see that the spark is only little, but if I put it around the flame, we will see if we can get a bigger spark happen.

Look at that, yeaaa! Because the flame has those ions in it, that means that we can break down a greater distance of air. This greater conductivity. It's awesome! You love doing this, right?

A strong enough electric field can actually extinguish the flame, but watch carefully what happens when the flame goes out. Just like in the flame, the opposite charges in the smoke are pulled in opposite directions. Now, while some may argue that a flame is not truly a plasma because it's not hot enough and it doesn't have a high enough density of ions, one thing is for sure: it does contain ions which have important electrical properties, which can be demonstrated if you have a strong enough electric field.