If you’re looking for an interesting but slightly dangerous experiment for your science fair project, you’ve come to the right place, with this project from the August 1938 issue of Popular Science. With just a few odds and ends from the hardware store, you’ll be able to cause an electric current to flow through glass.

You’ll need some copper wire (which can be cannibalized from the electric light you’ll be using, as well as some glass tubes.  If you can’t find the glass tubing locally (or “borrow” a couple from your science teacher), then one of the least expensive options appears to be these reusable glass drinking straws from Amazon or these glass test tubes.

You’ll need a lamp cord similar to the one shown here, or you can simply use a normal desk lamp.  Cut one of the two wires leading to the lamp (or plug it into an extension cord and cut one of those two wires), and strip the insulation off the end of the two wires.  Insert each wire into a glass tube.

Of course, glass is an insulator, so the lamp won’t work when plugged in.  But when you hold the two glass tubes next to each other and heat them in a bunsen burner, electricity will begin arcing through the molten glass, and the light will come on.

It appears that what’s happening is that an oxide of the copper is mixing with the molten glass, and the current is using this as an electrical path.  When you remove the glass from the flame, the light will stay lit until the glass again solidifies.

Warning:  This experiment uses household electricity, which can kill you if you’re not careful.  Don’t work in a wet area or anyplace where you can touch a metal object.  Whatever you do, don’t let anyone touch either of the two exposed wires.  When you’re done with the experiment, cut the plug off your modified cord so that some younger kid won’t plug it in and get electrocuted.  Do this experiment only with adult supervision.