Re: Puncture voltage

Tesla List wrote:
> >From al263636-at-sal.itesm.mx.pupman-dot-comFri Aug 23 22:42:41 1996
> Date: Fri, 23 Aug 1996 09:49:29 -0500 (CDT)
> From: Jorge <al263636-at-sal.itesm.mx.pupman-dot-com>
> To: Tesla-List <tesla-at-pupman-dot-com>
> Subject: Puncture voltage
> Hi,
>         Im fairly new on building Tesla Coils, i recently built a small
>         one, it uses a 9000, 30ma neon sign transformer. My problem is
>         with the cap, i live in a small town and theres no where i can
>         get the poly to build the caps, so instead i used 1/8" window
>         glass, i sumerged the cap in oil and i also spreaded some in
>         between the plates, my question is ? Can the cap hold and for
>         how long ?.
>         Could some one please answer, i know this must be an easy
>         question for some of you, but im new at this some and im a
>         little nervous turning on the coil and have the cap blow up.
>         Thanks
>         Jorge Fuentes
> **********************************
> *    "World without end,         *
> *     From beginning to the end, *
> *     We are alive,              *
> *     Forever."                  *
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As long as you don't run the cap for too long a time, it should be OK.
Glass has a nice high dielectric constant, but unfortunately is very
lossy in Tesla Coil applications. This loss tranlates into heat. Any
imperfection in the glass (particularly "bubbles") causes even more
localized heating. If you run the coil too long, the heating causes the
glass to begin to conduct, starting a runaway condition which rapidly
punctures the glass in the weakest area, usually fracturing it in the

You may want to look at using wine-cooler bottle salt water capacitors.
These are very inexpensive, and very easy to fix if you lose a bottle -
even small towns will ALWAYS have an inventory of these.

Good luck, and safe coilin' to ya!

-- Bert --