By Anupum Pant
Let me just not say anything before I make you watch this video today:
In the video, a Nickel ball is heated using a torch and is dropped into a bowl of water. As the hot ball touches water for the first time, it makes a certain “Ping” sound. It enters the water and gets covered in a bubble sort of thing. As it cools and the bubble is lost, that “ping” sound comes back again. The “Ping” repeats several times and is fun to hear a metal ball do that!
Why does it form a Bubble cover?
This happens because the metal that is dropped into water is extremely hot and makes the water around it vaporize. The vapor formed around the ball acts as an insulator and doesn’t let the water touch the metal ball. This is the same effect that lets dip your hand in molten lead or Liquid Nitrogen without getting harmed by it. The same thing happens when you drop water on a hot pan – it dances.
This effect is called the Leidenfrost effect and I’ve covered it in an article before…
I’m not sure what exactly causes the “Ping” sound. If you know or have any theories, please tell me in the comments below.
CrashCourse in Quenching
Well, if I’d have wished to piss you off with jargon, I’d have said: “You just watched a hot Nickel ball being quenched in water”
Yes, quenching. Quenching is the name for making a hot metal cool very quickly. It is pretty interesting to know why some one would, with great effort, heat a metal, and then choose to drop it in water to cool off!
Cooling a hot piece of metal very quickly makes it extremely hard. So hard, that the same process is used to make the hard edges of swords that don’t get damaged even if they are used to cut metal!
There is so much more I wanted to write about the process, but I feel this isn’t the right place for it. Let me leave it for some other day.