Re: cap material question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 6/10/01 11:43:20 PM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:

> Original poster: "Will Daniels by way of Terry Fritz <twftesla-at-qwest-dot-net>" <
> tesla_is_god-at-37-dot-com>
>  
>  I know most people use PE as their dielectric but, I was looking through a
>  
page(http://www.datasync-dot-com/~ignatz/electro/teslacoil/platecap/homadecaps.h
>  tm) at the dielectric material graph section and I noticed how good mylar's
>  ratings were.  I know it must have been tried on a cap with a puncture
>  voltage of 7500 per mil  and a better dielectric strength than PE.  Has
>  anyone used mylar on a cap before?  I looked around and 
>  http://www.discount-hydro-dot-com/mylar.asp
>  is selling mylar for pretty cheap.  Is this the right stuff?  Mylar seems
>  far too good to be true.  If anyone could shed some light on this subject
>  I'd appreciate it.
>       Thanks,
>            Will Daniels
>  

Will,

Your guess is correct, Mylar *is* too good to be true.  It has very
high losses at Tesla coil frequencies, which causes it to heat
up and give shorter spark lengths.  I did a test of the popular
0.01uF Fair Radio cap which I think is Mylar.  It heated up and
gave 15% shorter sparks than my Maxwell polypropylene caps.
Mylar caps can short out and leak or explode from the internal
heating.

John Freau