Defining fire as plasma is a topic that divides even experts in physics and chemistry, so the most popular expressions point to “almost plasma” or “partial plasma”. What they do agree on is that fire heats and burns… but what if it were possible to create cold fire/cold plasma? Under the right conditions, cold fire freezes what it touches, and the YouTube channel The Action Lab has two videos with excellent demonstrations.
Fire and Plasma
“Fire: Accelerated oxidation of a material under combustion. The flame is the part of fire that emits visible light, and the process is exothermic, so it also emits energy in the form of heat.”
But if we try to explore its relationship with plasma, the story gets complicated. For some, when a gas reaches the minimum temperature that allows it to be seen, it is a plasma. For others, everything depends on the level of ionization, and in the case of fire, it would not be that high.
So… half plasma? Semi plasma? If that sounds too confusing, let’s look for common ground. Fire and plasma are hot and the idea that they could turn into something “cold” is contradictory… unless we tweak their conditions a bit. That’s what they did on the channel The Action Lab, the same one of the drone inside an elevator and the Internet signal through water. Cold fire!
Cold Fire!
It all starts with an electrode, which reaches tens of thousands of volts. The potential is so high that the gas around the electrode ionizes.
The key to turning that fire/plasma cold is to displace thermal energy while retaining free electrons. For this, a gas that ionizes easily and has superior thermal conductivity is needed. In a word, helium.
By adjusting the gas flow, its circulation becomes fast enough to keep ions from accumulating thermal energy, but not free electrons.
So why don’t those electrons burn us? The answer is that they don’t have the necessary mass. That makes cold fire an excellent sterilizer, destroying surface viruses and bacteria without burning material.
The Fire That Freezes Things
However, the experiment in the first video is at room temperature. To create cold fire that freezes what it touches, the solution is to drastically reduce the temperature of the gas.
At this point, a whole range of possibilities opens up, but The Action Lab followed the path of dry ice, placed over a copper coil. This causes the temperature of the helium to drop to about -78 degrees Celsius.
The hardest part is filming the freezing (it looks better with lots of light, even though it “covers” the plasma), but the shortcut was to wet the objects before placing them near the electrode.
