Zap!!! …goes the finger

Beware, owners of those plasma-dome thingies: I just discovered how to fry my own flesh with one.

If you’ve never played with a plasma globe before, the basic idea is that there’s a glass sphere* with a partial vacuum and a central electrode inside. When driven by a high-frequency, high-voltage AC current, ribbons of plasma reach out to the sides of the globe. Bringing a conductive object (such as one’s own hand) near the glass “attracts” the purple ribbons of light toward whatever it is. A slight warmth can be felt emanating from the dome after a short while. In a nutshell… cool!

Now, if you just barely touch your finger to the globe, you can hear a buzzing sound from the electricity that is arcing between the small gap of air between your finger and the glass. Look closely and you can see:

Isn’t that neat? It starts to sting slightly after a long while, but barely. Being the curious type, I started touching other objects to the glass to see what would happen. Predictably, it would seem that only conductive objects had any affect…furthermore, a small conductive object, like a pen clip, wouldn’t attract any filaments of plasma unless I was touching it, connecting it to my whole, 70%-water body. I then found that if I held the (plastic) pen to the globe without touching the (metal) clip, I could then touch the clip with my other hand and get some sparks from that…the clip was the new electrode! Cool! Hey… what’s that smell?

Turns out that concentrating the output of the globe onto the tip of a pen clip isn’t necessarily such a good idea. It took me awhile to realize it, but for some reason this arcing — which was orange now (cool!!!) — was burning my skin. And I have the burn marks to prove it!**

Being the experimenter that I am, I was contemplating wrapping a sheet of aluminum foil around the globe and seeing what would happen, but having researched plasma globes for this story, I’m satisfied that it would have the desired effect of being even more dangerous, enough that I won’t do it.