Pic 1 A 4.7 inch secondary: coil #1
The basic materials used in a Tesla coil are illustrated. The primary is generally copper heating pipe, although strip can be used on large tesla coils, while the secondary former is a suitably sized tube of Acrylic. Avoid black plastic however as this has carbon added.
Acrylic tube needs a coat of varnish before any winding, so as to help the wire to grip.
This Variac (rated at 20 amp) easily handles in excess of 30 amps without any trouble. It was also a back breaking monster for people to move around, until it went on wheels.
One of the four base's securing lugs was broken off by the courier company unfortunately, and it was only then I appreciated that the chassis of the unit was built using a 1" by 2" cast iron frame!