My 6 inch secondary: coil number two


The basic materials used in a Tesla coil are illustrated above. The primary is generally copper heating pipe, although copper strip can be used on large coils, while the secondary former is a suitably sized tube made of an insulating material like Acrylic. Avoid black plastic however as this has carbon added.
I find Acrylic tube is reasonably priced and is handy to use, but it needs a coat of varnish before you wind, so as to help the wire to grip.