The Turn Of The Century Electrotherapy Museum http://www.electrotherapymuseum.com Wax-Impregnated / Oil-Filled Tesla Secondary Coils Slightly new twist on an old concept typically used by Elihu Thomson. Paraffin wax was used instead of linseed oil or kerosene, to keep down the mess!   A simple setup.  3.5" diameter PVC secondary coil, close-wound with 26 AWG wire.  It was placed in the centre of a 4.5" diameter piece of PVC, capped and then filled with wax.  The caps were sawn off afterward. Testing coils without a topload to start... Sparks were around 9-10" long with around a  kilowatt of power using my Tesla Coil tuner. Here is the ridiculous experimenter behind this website... (C) Jeff Behary - 15. March 2008