Subject: Re: Gradually lightning neon. How?

From: [email-masked] (BillyFish)
Date: 29 Jul 1995 00:56:09 -0400

In article <[email-masked]>,
0396103-delden <[email-masked]> wrote:
>Some time ago I was in a novelty store where they sold some neon things.
>One of the neons was a figure made from glasstube that began burning at
>one end of the tube and then slowly followed the tube (with its lightning
>path) to the other end (and was totaly lit then). Then it made its way
back
>again, slowly fading from fully lit to totaly out. How is this done? I've
>always thought that the ignition of a neon tube was some kind of chain-
>reaction and could not be controlled. After all everything takes place
>between two electrodes.....
>
>In another tube (saw it somewhere else) they were able to send 'light
pearls'
>down the tube. I looked like a continuous stream of small light balls
going
>through the tube. A very cute effect.

Although I do not know how the effect was achieved, one possibility for
the first one is by current control.  In glow discharges, the area of the
glow is roughly proportional to the current.  It is only when the glow
covers the entire cathode, that additional current starts the transition
to arc discharge.

William Buchman