[Corvettaholic]

So the mention of misch metal got me really interest (add it to the list, huh?) in sparks! So when I flick my lighter, it makes sparks. Easy enough. What exactly IS a spark? Does it have mass? Is it energy?

If its mass, that means its gotta come from somewhere, is it from the misch metal, or from the metal striker thing? What if I used different metals, say had a magnesium striker instead of iron, or whatever they use? Sounds like a real bad idea and I won't do it, but I'm just curious. If sparks are pure energy, that means I should easily be able to manipulate them with a strong magnetic field, and I got a great idea for a light-show device.

[gregpawin]

A spark is just the appearance of a plasma, or excited bunch of molecules that are going through some chemical reaction and giving off light, or being ionized by a high voltage electric flow.

[hmx9123]

In an electrical sense, yes, but in a chemical sense, especially in the misch metal sense, you may be seeing small particles with surface burning going on.  The burning itself of course is low temp plasma, but it is many times attached to tiny particles as they fly through the air.  The sparks from flint and steel are actually tiny flecks of iron rapidly oxidizing (burning) in air.  This particulate burning is what's responsible for the beautiful willow effect of many fireworks.  Think about sparklers, too.  These are nothing better than pieces of aluminum and steel rapidly oxidizing through air and bouncing down on the ground.  I've got a great picture of a sparkler from a couple of years back doing some chem demos.

[hmx9123]

Oh yeah, I found some awesome charcoal stars.  Beautiful example of sparking.    The middle two are examples of sparking, but they are not charcoal stars.  Only the overreaching one is that.

[Corvettaholic]

Plasma?! Wow, never thought I'd see something get that hot, and I guess I see it quite a bit from my lighter. So sparking is all based on chemical (as in a sparkler), and not electrical. But once the particulate has been shot out, and is burning really freaking hot, does it have any electrical properties? I imagine being so hot, any ferrous properties are right out.

Given all this new stuff to me: If a spark is superheated whatever at a plasma state, then an arc would really be just a big long thingy of sparks, right? And just to refresh my memory, to ionize is to take away an electron, therefore giving you a positive ion, right? Can there be negative ions?

[hmx9123]

Plasma is more common than you think.  Ever look at a flame and wonder whether it's a solid, liquid or a gas?  It's actually just low temperature plasma.  You're thinking of high-temperature plasma, the really energetic stuff.

Sparking is not always based on chemicals; in your lighter, it happens to be.  However, as greg pointed out, you can get sparking from electricity as well.

Everything has electrical properties.  How well a substance conducts electricity is just one of those properties.  To what are you referring?

Sparks aren't necessarily superheated.  Chemically, they're burning chunks of whatever flying through the air, and electrically they're ionized particles of air (or whatever medium you're using).  (These are gross terms, as ionization is of course chemical when you get down to a molecular sense).

I suppose you could think of an electric arc as a long chain of sparks, although it might be more suitable to think of it as a long chain of ionized atoms.  Greg could probably help you more with that; he's more of the physics guy.

If you make a positive ion, you have to make a negative ion.  It's conservation of charge.  Take a look at the salt on your table.  Dump some into water.  You've just generated positive and negative ions.  The sodium ion is positive, the chloride ion is negative.

[Corvettaholic]

I was just reading about conservation of charge earlier today, thats a very good point. And about plasma, yeah, I always think about the really high powered stuff. Like the sun. I've seen plenty of sparking from electrical sources, such as power supplies in computers. So sparks are not created equal then, do they ALWAYS involve a tiny bit of burning matter? When I think of "energy" I think of light, heat, sound, or electromagnetic waves. When I think of "matter", I think of anything I didn't previously mention. As I understand a plasma, its the next state above a gaseous state. So what kind of rules does a plasma follow compared to a gas or liquid? Can it flow, be magnetic, or stuff like that? Now I'm starting to visualize plasma as simply "fire". Then I get to thinking what rules that fire has to follow. Am I on the right track?

The end result of this questioning is trying to figure out if I can make a stream of sparks flow in neat curves mid-air through the use of magnets, and generate sparks via a metal grinder or (now that I know about it) misch metal.

[gregpawin]

As with all applications of language on physical phenomenon, the definition of spark is so broad and general, it almost has no meaning at all.  I would guess its meaning to most people is just something like a pointlike flash of intense visible light, which can be caused by a whole litany of things.  Probably, most people see the sparks in fireworks/sparklers when they think of it, which are most of the time pieces of metal containing particles at really high tempeartures, which are hmx's forte.  

However, you must remember to separate the idea of temperature with heat, like how most people should stop thinking high voltage or high current is automatically dangerous.  While the temperature of that spark might be really high, it has such low total heat, that it does you no harm when it falls on your arm when handling a sparkler; by the same token, when you make a spark by touching a doorknob on a dry day, you are involved with high voltage but with a tiny amount of actual flow of electrons.

Interestingly, plasma is the predominate form of matter in our universe because it is the natural form of matter in environments of intense energy, as in stars.  But sometimes I wonder, if those astronomists are just assuming everything that is in the universe can be seen, which limits things down to radiation emitting objects.

Yes, plasma can be controlled by using electric or magnetic fields, because they are defined as excited collection of positive and negative ions.  Problem is with making a controlled stream from a sparkler is that by being excited, they are giving off their energy/heat all the time.  You are sitting in a bath of relatively cool fluid while the sparkler is giving away its chemical energy as heat and light.  For a sustained production, you need to keep adding energy.  And that spark has just used up its own energy in a pretty much irreversible reaction.

[Corvettaholic]

Yeah, I suppose a spark would be fairly irreversible  

The way I thought of to constantly add energy was to have a metal disc, constantly spinning, pressed against another metal surface. Sure I'll have to replace the sparking disc periodically, but that should count as continually adding energy. Once the sparks are generated, I want to be able to move them around, at least until they expend all their energy. Good point on the temperature vs heat thing, never really thought about that before.

[Scratch-]

The large falling sparks from shooting fireworks are made by superheating iron spheres until they burn. You might be able to do something similar with a high-energy reaction. If you have a large enough sphere you might still be able to pull it around with a magnet before the core of the sphere gets too hot.

[Corvettaholic]

I was thinking of using this mysterious "misch metal" to have some fun. Figure if it works in my lighter, should work fine as a clutch disc. Spin with a starter motor, and press it into an iron plate. Tons of sparks that way. I think maybe I'll just wave a powerful electromagnet around it to see what happens. Speaking of magnets, time to visit the physical chemistry forum  

[hmx9123]

"The large falling sparks from shooting fireworks are made by superheating iron spheres until they burn. You might be able to do something similar with a high-energy reaction. If you have a large enough sphere you might still be able to pull it around with a magnet before the core of the sphere gets too hot. "

What are you talking about?  Iron spheres?  Most fireworks don't use iron, actually.  Sparks come from finely groud metals, charcoals, and other materials.  While you could use iron, most don't.  The closest thing I can think of is sparklers that use both Al and steel for sparks.  Aluminum is probably the most common sparking agent in fireworks.  But superheating iron spheres?  I think you're misinformed.  Although some compositions call for certain types of metal particles, like flake or spherical, none that I know of use iron.  It doesn't spark that well.  Iron titanium flakes do a great job at sparking, though.  Also, superheating isn't what really starts the reaction; powerful oxidizing agents are intimiately mixed with the metals to create the burn, then flame touches them briefly and away they go.  There isn't any superheating or conductive heating initiating the firework.

[Corvettaholic]

So fireworks are just a fancy reactive metal + less reactive metal compound reaction right? The first thing I learned about those types of reactions is thermite, but I assume it applies to a lot more benign uses, such as fireworks. Now that I think about it, you DID mention that a thermite reaction throws a LOT of sparks, so I assume thats true of any similar type of reaction? Not that I want to do that to create sparks, too dangerous. Now misch metal thats used in lighters, is that something I can order somewhere?

[Scratch-]

I saw it on a movie about fireworks. These are the big fireworks that the pros shoot up in the air for independence day.

[hmx9123]

Fireworks are a lot of different things.  I think perhaps what Scratch was thinking of was round stars; these are small sphere-like balls of compositions that fly through the air from the large commercial fireworks emitting sparks as they burn.

Compositions of fireworks generally consist of:

- an oxidizing agent
- a fuel
- a colorant
- a binding agent

The oxidizing agent oxidizes the fuel and the coloring agent; sometimes the burning of the fuel excites the colorant to emit colors, other times it does not.  The binding agent is in small amount and just holds things together.  You can also add sparking agents, chlorine donors (to enhance color), among other materials.  The fuel can be a metal, or it can be an organic compound.  Sometimes, the fuel is also the colorant and the sparking material, other times it is not.  rec.pyrotechnics has a lot of good information on this in their archives.