Plasma Colouration? (Imperial Weapons)

[MarcoSkoll]

The color of plasma is going to depend on the chemical composition of whatever is generating it.

I'll take it you went tl;dr on that whole post I wrote on what causes the colour of plasma.

So here's the tl;dr version:
To the perceptions of the human eye, the chemical make-up of a plasma is irrelevant in deciding what colour it is. The only important factor is the temperature. The hotter it gets, it moves from red through yellow to pure white. (And if it gets insanely hot, a faint blue - a bit ironic, given our normal perceptions of red as a warm colour and blue a cold one). If you want to know why, my last post will explain it in plenty of detail.

So if you want to paint it an inappropriate colour (anything that is not a natural spectrum for black body radiation), the appropriate excuse is "artistic licence", not "different chemicals".

[Soldado]

I've always thought of plasma to be either pale yellow (like a sun) or a pale purple/lilac

Emperor Children's plasma (actual plasma cutting machine)

And pretty much what MarkoSkoll wisely said (in both posts, even the TL;DR ones).

In most of the 40k artwork I've seen, plasma is white-blue-ish, and, when I going to paint one, some day, mine will be the classic one, because purple-pinky does not fit very well with World Eaters. But who knows...

[DietDolphin]

To the perceptions of the human eye, the chemical make-up of a plasma is irrelevant in deciding what colour it is. The only important factor is the temperature. The hotter it gets, it moves from red through yellow to pure white. (And if it gets insanely hot, a faint blue - a bit ironic, given our normal perceptions of red as a warm colour and blue a cold one). If you want to know why, my last post will explain it in plenty of detail.

I think the point is that each plasma gun is at the same temperature but because of possibly different chemicals used, a different colour could be observed as each element/molecule has different ionization levels.

I mean a forgeworld isn't going to make cooler plasma guns just so they can get the same blue as everyone else just because they are using a substance easier to ionize.... Unless of course divergence from standard "imperial plasma blue" is heresy.

[Friedrich von Offenbach]

What no one seems to have mentioned is painting the plasma 'part' silver, like a metal casing with groves for cooling like an oil heater sort of thing. The plasma doesn't have to be out in the open, as wouldn't it just fall out of the gun? I personally paint plasma blue but i have a friend who does silver and it still fits in nicely to most colour schemes.

Totally irrelevant, but i was just thinking: Plasma is super hot. hot stuff rises because its less dense. Shouldn't that mean when you fire a plasma gun it should go straight up into the upper atmosphere?

[DietDolphin]

Totally irrelevant, but i was just thinking: Plasma is super hot. hot stuff rises because its less dense. Shouldn't that mean when you fire a plasma gun it should go straight up into the upper atmosphere?

Protip: applying real world logic to sci-fi always ends in disappointment, so try not to think about it too much

[AndrewGPaul]

I paint the "magnetic containment coils" on my plasma weapons as a copper colour. Like Friedrich von Offenbach above, I'm not happy with the "flourescent lightbulb" look of coloured coils. I save the blue glow for the muzzle and surrounding vents.

Actually, even the copper look is probably silly - they'd either be the colour of the rest of the gun or black, I would think, but that would look a bit boring.

Friedrich, 40k plasma guns have some technobabble about magnetic fields which keeps the actual plasma from dispersing before it contacts the target.

[=Angel=]

how the hell did a hive ganger get ahold of a plasma cannon?

And why would a hive ganger know what a sun looks like?

[MarcoSkoll]

I think the point is that each plasma gun is at the same temperature but because of possibly different chemicals used, a different colour could be observed as each element/molecule has different ionization levels.

As I have now said more than once: To the human eye, only the temperature affects the colour of plasma. And Ionisation =/= Temperature.

If something is at 4000 Kelvin, it will look the same colour regardless of what it's made of or how that something is ionised. Yes, under very fine spectral analysis, different materials will leave different specific frequencies missing, but these spectral lines are completely invisible to the human eye, which does not have the necessary colour resolution to make them out.

If plasma is a different colour, it is a different temperature. It's not because it's a different material, a different ionisation or any of that. Sure, it might well be, but this will not be why it's a different colour.

But as I've already said, paint it what colour you like. However, justify your choice with artistic licence, not pseudoscience.

[ChrisMurray]

As much as I love seeing a debate about science, I don't think it should dominate what colour you paint your minis. Rule of cool trumps here. Although I personally like green plasma weapons.

[Iron_Lord]

As I have now said more than once: To the human eye, only the temperature affects the colour of plasma. And Ionisation =/= Temperature.

If something is at 4000 Kelvin, it will look the same colour regardless of what it's made of or how that something is ionised. Yes, under very fine spectral analysis, different materials will leave different specific frequencies missing, but these spectral lines are completely invisible to the human eye, which does not have the necessary colour resolution to make them out.

If plasma is a different colour, it is a different temperature. It's not because it's a different material, a different ionisation or any of that. Sure, it might well be, but this will not be why it's a different colour.

Why does a tube full of neon plasma glow a very different colour from a tube full or argon plasma? Temperature alone does not account for it.

http://en.wikipedia.org/wiki/Plasma_(physics)

Other factors may matter- even visually.

[MarcoSkoll]

Okay, I was overgeneralising. If you have a cool plasma such as those in a gas discharge lamp, yes, it can be different colours. In such cases, you are seeing the emission spectra.

However, if you have a hot plasma (the relevant point of discussion here), the black body radiation produced would have an effect many orders of magnitude greater than any other factor that affecting the colour of the light produced. (It's like putting a rose on a pile of fermenting manure. It's still going to smell awful.)

[DietDolphin]

As I have now said more than once: To the human eye, only the temperature affects the colour of plasma. And Ionisation =/= Temperature.

I didn't say this at all. However you are right about the colour after having another bit of a read up on plasma at high temperatures.

However...

Why does a tube full of neon plasma glow a very different colour from a tube full or argon plasma? Temperature alone does not account for it.

http://en.wikipedia.org/wiki/Plasma_(physics)

Other factors may matter- even visually.

Which was why I initially got a bit mixed up. So after going re-reading my stuff on plasma i'll try to break it down in Layman's terms (though your post was great Marcoskoll, it is a bit... overwhelming).

-At relatively low temperatures the colour of Plasma depends on the gases composition, this is due to the gas ionizing (the definition of a Plasma), releasing elections which them bind with other molecules to form neutral atoms. As the atom has gained an electron and dropped energy levels light is emitted. What light is emitted will depend the ionization level of the gas and what gas it is. Examples are neon lights.

-At high temperatures, Plasma gas effectively becomes a black body radiator to the human eye. This means it will be radiating nearly every wavelenght of light. This means white light will be observed as white light is just a combination of all colours of light. Example: the sun

[Born Again]

What no one seems to have mentioned is painting the plasma 'part' silver, like a metal casing with groves for cooling like an oil heater sort of thing. The plasma doesn't have to be out in the open, as wouldn't it just fall out of the gun? I personally paint plasma blue but i have a friend who does silver and it still fits in nicely to most colour schemes.

Totally irrelevant, but i was just thinking: Plasma is super hot. hot stuff rises because its less dense. Shouldn't that mean when you fire a plasma gun it should go straight up into the upper atmosphere?

Re: the first part, I was just looking through the 2nd FW Badab War book, and there is a picture of a Salamander in there with orange coils on his plasma pistol... however, all the wargear diagrams show plasma weapons as being silver. It could be the coils are metallic in appearance when inactive, and glow when the weapon is fired and for a short 'cool-down' period after. As to what colour... I'd say it depends on what gives the most dramatic contrast with the rest of the model's colours.

As to the second part... there's some logic in that, yes. However, planes should also fall out of the sky, they are kept there by force exerted by the engines and the way that interacts with air pressures over the wing. In the same way, the plasma is accelerated at a very high velocity out of the gun... so it probably goes up, eventually, in the same way a bullet will eventually drop to the ground. An odd thought.

Having said that, my knowledge of physics is rated only a tiny amount above "nothing" and someone else can feel free to correct me there

[Pilgrim]

Totally irrelevant, but i was just thinking: Plasma is super hot. hot stuff rises because its less dense. Shouldn't that mean when you fire a plasma gun it should go straight up into the upper atmosphere?

Do flamethrowers immediately jet their payload into the sky just because it's a bit hot? No. Likewise for lightning bolts shooting downwards, despite their temperature, and lava not immediately leaping off the ground.

In the case of plasma bolts, the velocity will prevent any alteration in course for the short term, meaning it won't start to disperse into the atmosphere until after it's hit its target. The creation of an ionisation channel through the atmosphere will also cause the plasma to preferentially follow this pathway instead of radiating in all directions (again, in the immediate term).

[DietDolphin]

Do flamethrowers immediately jet their payload into the sky just because it's a bit hot? No. Likewise for lightning bolts shooting downwards, despite their temperature, and lava not immediately leaping off the ground.

In the case of plasma bolts, the velocity will prevent any alteration in course for the short term, meaning it won't start to disperse into the atmosphere until after it's hit its target. The creation of an ionisation channel through the atmosphere will also cause the plasma to preferentially follow this pathway instead of radiating in all directions (again, in the immediate term).

Just thought I would point out that Flamethrower fuel and lava are both liquids and lighting is a current of electricity. They are all completely different to Plasma.

Plasma is basically a very hot gas (to the point of ionization) so it would work like a smoke gun. Sure the initial velocity will give it a little distance but because of air resistance alone it won't get far will dissipate and will rise. Also you can't have a bolt of gas, thats sci-fi nonsense.

The only way I could see it working is if it did fire solid bolts that contained plasma in them.

[Eldartank]

Contrary to the colour choices of pre-schoolers, the sun is not yellow. It merely appears yellow because of the atmospheric scattering of blue light.

It's easy to prove that its light is overall white (or what the human eye perceives as white) - we can only perceive a colour if the relevant wavelengths are being reflected back, and as we can see all colours in daylight, the full range of visible frequencies must be present. (Obviously excepting spectral lines, but these are far too fine to be perceived by the human eye.)

Seriously? What's next? You going to try telling us that nonsense about the Earth being a globe instead of flat? Maybe you can also try to convince us that the Earth is not actually the center of the universe.... (Just kidding!)

[MarcoSkoll]

Also you can't have a bolt of gas, thats sci-fi nonsense.

Plasma is electrically conductive. As it will carry a current, it's possible to shape it with electromagnetic forces. A radial induced current would compress it in on itself, and make it coherent - as long as the current lasted, at least. The exact same technique is used to "shrink" coins without any physical contact.

The approach could actually be combined with inductive coilguns, shaping and accelerating the plasma at the same time. So it's not as much sci-fi pseudoscience as it sounds - it's doable, if difficult.

[DietDolphin]

Plasma is electrically conductive. As it will carry a current, it's possible to shape it with electromagnetic forces. A radial induced current would compress it in on itself, and make it coherent - as long as the current lasted, at least. The exact same technique is used to "shrink" coins without any physical contact.

The approach could actually be combined with inductive coilguns, shaping and accelerating the plasma at the same time. So it's not as much sci-fi pseudoscience as it sounds - it's doable, if difficult.

Uh I was thinking of a bolt as in a solid bolt used in a crossbow, silly me. But like you said it would be difficult. You would have to compress it quite a bit for it to effectively cut through the air though, which could even change the state of the matter depending on the temperature and compression.

Also about the whole rising thing. It will largely depend on whether the Plasma gas used is denser or less dense than the air around it rather than the heat.
Heat does make things more energetic and less dense, but CO2 is still heavier than 02 for example.

[MarcoSkoll]

...Which could even change the state of the matter depending on the temperature and compression.

This does seem intuitive - knowing that both temperature and pressure affect states of matter, such as water boiling at a lower temperature in the thinner air up mountains - but there's something called a supercritical fluid.

As liquids are heated, they get less viscous and dense. As gasses are compressed, they get more viscous and dense. At a particular point on the temperature/ pressure graph (known as the critical point), these two cross over, and there's no difference between a heated liquid and a compressed gas. You get instead what's known as a supercritical fluid. Something that, no matter how much you compress it, it can't become a liquid, and no matter how much you heat it, it can't become a gas.

This is why compressing alone can't turn air into a liquid, because it's above its critical temperature. It has to be cooled. (Or compressed and cooled).

Plasma is more than hot enough that no amount of compressing would turn it into a liquid. You could compress it down to crazy densities (like is the case in the sun), and it'd still remain a plasma.

[NixonAsADaemonPrince]

As has already been said, "colours" are simply terms for the variations in the narrow band of the electromagnetic spectrum which humans eyes can perceive. So you can paint the plasma any colour, or leave it "black" (i.e No visible photons being emitted).