Re: Colored sparks
From: Jim Lux[SMTP:jimlux-at-earthlink-dot-net]
Sent: Thursday, December 11, 1997 4:29 PM
To: Tesla List
Subject: Re: Colored sparks
Tesla List wrote:
> From: Gary Lau 10-Dec-1997 1244[SMTP:lau-at-hdecad.ENET.dec-dot-com]
> Subject: Colored sparks
> Last night I placed a small wad of paper towel, soaked in water, and
> thickly covered with table salt on my torroid such that this would
> constitute a breakout point. The streamer that originated from this
> point was beautiful - BRIGHT sodium-yellow for about the first foot of
> arc, then fading to the usual blue-violet. Try it!
> I'm anxious to try salts of other metals - copper, barium, and strontium
> come to mind.
I've played with this at some length. Before the advent of xenon arc
spotlights and dichroic filters, they used cored carbon electrodes in an
arc, with the core containing the appropriate compounds to color the
I've tried soaking objects (e.g. a tennis ball) in various salt
solutions and placing it in a drawn arc or jacobs ladder to produce some
novel special effects. I've also sprayed fine mists of the solutions in
either alcohol or water. Alcohol evaporates faster but is flammable.
The idea is to put the mist in the air, let the solvent evaporate, and
have microscopic particles of the salt suspended in the air. If the
particles are small enough, they won't settle out.
For colors try:
Strontium - deep red, scarlet
Calcium - orangish red
Barium - yellowish green
Copper - green or blue (blue with Chloride ion)
Sodium - bright yellow
Violet - potassium (it is weak though, and will be masked by the
nitrogen in the air).
As to toxicity, Barium compounds are most toxic. However, the total
amounts aren't all that high. A fairly dense mist is a few tens or
hundreds of milligrams per cubic meter, and a milligram of solution
contains micrograms of the salt.