toroid discharge

Subject:  toroid discharge
  Date:   Fri, 13 Jun 1997 11:17:05 PDT
  From:  "Mad Coiler" <tesla_coiler-at-hotmail-dot-com>
    To:  tesla-at-pupman-dot-com

All, I have heard before about the breakout voltage of the toroid, was 
wondering if anyone has any formulas or rules of thumb regarding how to 
determine breakout voltages or power levels for optimum performance for 
different toroid sizes. I have several different toroids I use on my 
coil. With the small ones that run at higher freq seem to work just 
fine, but when I put a big toroid on it (and I re-tune!) to get the 
lower frequencies, the toroid stops free-arcing. But I know there is 
voltage there because as soon as I place a grounded rod in proximity 
with the toroid it bolts out pretty strong. Can anyone give me any 
advice on what is going on and how to find out my optimal toroid size?