So you love experimenting with spectrum tubes? The Elenco STPS-1 Spectrum Tube lets you do so in a safer fashion. It lets you study spectral lines of pure substances. The power supply lets you run 10″ spectrum discharge tubes. It has specially designed sockets to eliminate risk of electrical shock.
So how does this work? Electrons inside the tube run from the negative pole to the positive pole and hit the gas atoms to cause them to light up. Different gases produce different colored lights. You can buy them for around $20 each.