Re: Paint breakdown at high voltage

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

Original poster: "Christopher Boden by way of Terry Fritz <teslalist-at-qwest-dot-net>" <chrisboden-at-hotmail-dot-com>


1. the "Mole Trails" are Carbon Tracks :) you can create a similar 
phenomenon in wood, plastic, and even the thin glass of a lightbulb :) It's 
the bane of the HV world. Carbon Tracks forming in the tar are the #1 cause 
of all NST failures.

2. Never, ever, paint an insulator, period. Black is the worst (and a 
common color for people to paint coil bits) but others have it to. It's not 
the metallic bits you have to watch out for, those are clearly labelled as 
such. It's the Carbon (there's that word again) that is mixed into the 
paint, or one of a thousand other ingrediants, that is either conductive, 
or conductive enough to work at HV.

The solution? Build a new gap.


Christopher "Duck" Boden Geek#1
President / C.E.O. / Alpha Geek
The Geek Group
www.thegeekgroup-dot-org
Because the Geek shall inherit the Earth!

Never doubt that a small group of thoughtful, committed citizens can change 
the world. Indeed, it's the only thing that ever has.


The ability to learn is older - as it is also more widespread - than is the 
ability to teach.
     - Both from Margaret Mead, 1901 - 1978





>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Paint breakdown at high voltage
>Date: Tue, 04 Feb 2003 11:40:36 -0700
>
>Original poster: "Christopher \"CajunCoiler\" Mayeux by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <cajuncoiler-at-cox-dot-net>
>
>
>Anyone else having problems with paint breaking down under high
>voltage?  I recently put a coat of paint on the outside of my RQ-style
>spark gap, and it goes nuts with arcing when a 15/30 NST is applied to
>test it... problem is, the arcing is on the OUTSIDE, around the heads
>of the bolts that hold the electrodes in.  I also notice some lines
>forming in between the bolt heads that closely resemble the trails
>left by a mole...although on a MUCH smaller scale.
>
>Next, I decided to make a simulation, to see what was going on under
>a controlled condition.   I took a left-over slice of PVC, and drove
>some screws and copper couplings in, making a simple replica of the
>original gap.  Then I attached the 15/30 NST to the two end electrodes,
>and connected the NST to my bench variac.  I cranked up the whole thing
>at the 0 setting of the variac, and slowly turned it up.  The hiss of
>corona was present, telling me all was well, all the way up to full
>voltage.
>
>Next, I covered the open ends of the pvc, and sprayed on 2 coats of
>the paint in question, letting each coat dry solidly.  Then I took my
>Fluke77 DVM, and tested to see if perhaps the paint was conductive at
>this point... it wasn't.  So I ran it through the voltage test as
>before, and this time, when the input was between 90 and 95 volts
>(probably about 11,250v and 11,875v out of the NST), it once again
>broke down, and started arcing and making mole trails.
>
>Anyone else encountered this?  Or is it just me again?
>If it is common, what workarounds are available?  BTW, I checked, and
>the paint is NOT a metal flake or metal particle type.