Make your own plasma

After a quite technical post the other day I’d like to share with you some more microwave entertaining. In that post we said that a rough classification for the states of matter is: gas, liquid and solid but there are more, for example plasma. A plasma is a gas where some of the electrons have been detached from their atoms. In that way in a plasma one has free negative charges moving (the electrons) and also free positive charges moving (the ionized atoms). For this reason, some fun electrical phenomena happen such as the filamentation that one can observe in a plasma lamp:

Filamentation in plasma lamp

As it turns out, you can create the same effect (at a smaller scale) in your own microwave. All you need to do is cut some grapes in halves, but not all the way through (just leave a small piece of skin holding together the two halves). Then dry the surface of the grapes with some kitchen paper and put them in the microwave for a few seconds.

Plasma grapes

Please beware that performing this experiment longer than a few seconds can be as dangerous as functioning the microwave empty and may result in permanent damage of your microwave oven. Also pay attention when taking the grapes out of the microwave because they will be very hot. This is the result:

Essentially what is going on is that the grapes are as little antennas, just like the light bulb was the other day. Their shape, composition (they are full of electrolytes) and size all conspire to make the electric field very strong near the grapes raising the temperature so much that the skin between the two halves burns and the air nearby is ionized creating a small plasma that provokes sparks.

Plasma grapes

You can actually see in the video that each grape bursts into flames exactly at the same spot in the microwave. This is because microwaves are not distributed uniformly and, since you need a high field to provoke this effect, you need to find the “hot spots” inside your microwave in order to create your own plasma.